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Croup
Other namesCroupy cough, subglottic laryngitis, obstructive laryngitis, laryngotracheobronchitis
The steeple sign as seen on an AP neck X-ray of a child with croup
Pronunciation
SpecialtyPediatrics
Symptoms"Barky" cough, stridor, fever, stuffy nose[2]
DurationUsually 1–2 days but can last up to 7 days[3]
CausesMostly viral[2]
Diagnostic methodBased on symptoms[4]
Differential diagnosisEpiglottitis, airway foreign body, bacterial tracheitis[4][5]
PreventionInfluenza and diphtheria vaccination[5]
MedicationCorticosteroids, epinephrine[4][5]
Frequency15% of children at some point[4][5]
DeathsRare[2]

Croup (/kruːp/ KROOP), also known as croupy cough, is a type of respiratory infection that is usually caused by a virus.[2] The infection leads to swelling inside the trachea, which interferes with normal breathing and produces the classic symptoms of "barking/brassy" cough, inspiratory stridor, and a hoarse voice.[2] Fever and runny nose may also be present.[2] These symptoms may be mild, moderate, or severe.[3] It often starts or is worse at night and normally lasts one to two days.[6][2][3]

Croup can be caused by a number of viruses including parainfluenza and influenza virus.[2] Rarely is it due to a bacterial infection.[5] Croup is typically diagnosed based on signs and symptoms after potentially more severe causes, such as epiglottitis or an airway foreign body, have been ruled out.[4] Further investigations, such as blood tests, X-rays and cultures, are usually not needed.[4]

Many cases of croup are preventable by immunization for influenza and diphtheria.[5] Most cases of croup are mild and the patient can be treated at home with supportive care. Croup is usually treated with a single dose of steroids by mouth.[2][7] In more severe cases inhaled epinephrine may also be used.[2][8] Hospitalization is required in one to five percent of cases.[9]

Croup is a relatively common condition that affects about 15% of children at some point.[4] It most commonly occurs between six months and five years of age but may rarely be seen in children as old as fifteen.[3][4][9] It is slightly more common in males than females.[9] It occurs most often in autumn.[9] Before vaccination, croup was frequently caused by diphtheria and was often fatal.[5][10] This cause is now very rare in the Western world due to the success of the diphtheria vaccine.[11]

Signs and symptoms

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Stridor
Inspiratory and expiratory stridor in a 13-month child with croup.
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Croupy cough
Croup cough in an 11-month child with croup.
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Croup is characterized by a "barking" cough, stridor, hoarseness, and difficult breathing which usually worsens at night.[2] The "barking" cough is often described as resembling the call of a sea lion.[5] The stridor is worsened by agitation or crying, and if it can be heard at rest, it may indicate critical narrowing of the airways. As croup worsens, stridor may decrease considerably.[2]

Other symptoms include fever, coryza (symptoms typical of the common cold), and indrawing of the chest wall–known as Hoover's sign.[2][12] Drooling or a very sick appearance can indicate other medical conditions, such as epiglottitis or tracheitis.[12]

Causes

[edit]

Croup is usually deemed to be due to a viral infection.[2][4] Others use the term more broadly, to include acute laryngotracheitis (laryngitis and tracheitis together), spasmodic croup, laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis. The first two conditions involve a viral infection and are generally milder with respect to symptomatology; the last four are due to bacterial infection and are usually of greater severity.[5]

Viral

[edit]

Viral croup or acute laryngotracheitis is most commonly caused by parainfluenza virus (a member of the paramyxovirus family), primarily types 1 and 2, in 75% of cases.[3] Other viral causes include influenza A and B, measles, adenovirus and respiratory syncytial virus (RSV).[5] Spasmodic croup is caused by the same group of viruses as acute laryngotracheitis, but lacks the usual signs of infection (such as fever, sore throat, and increased white blood cell count).[5] Treatment, and response to treatment, are also similar.[3]

Bacteria and cocci

[edit]

Croup caused by a bacterial infection is rare.[13] Bacterial croup may be divided into laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis.[5] Laryngeal diphtheria is due to Corynebacterium diphtheriae while bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis are usually due to a primary viral infection with secondary bacterial growth. The most common cocci implicated are Staphylococcus aureus and Streptococcus pneumoniae, while the most common bacteria are Haemophilus influenzae, and Moraxella catarrhalis.[5]

Pathophysiology

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The viral infection that causes croup leads to swelling of the larynx, trachea, and large bronchi[4] due to infiltration of white blood cells (especially histiocytes, lymphocytes, plasma cells, and neutrophils).[5] Swelling produces airway obstruction which, when significant, leads to dramatically increased work of breathing and the characteristic turbulent, noisy airflow known as stridor.[4]

Diagnosis

[edit]

Croup is typically diagnosed based on signs and symptoms.[4] The first step is to exclude other obstructive conditions of the upper airway, especially epiglottitis, an airway foreign body, subglottic stenosis, angioedema, retropharyngeal abscess, and bacterial tracheitis.[4][5]

A frontal X-ray of the neck is not routinely performed,[4] but if it is done, it may show a characteristic narrowing of the trachea, called the steeple sign, because of the subglottic stenosis, which resembles a steeple in shape. The steeple sign is suggestive of the diagnosis, but is absent in half of cases.[12]

Other investigations (such as blood tests and viral culture) are discouraged, as they may cause unnecessary agitation and thus worsen the stress on the compromised airway.[4] While viral cultures, obtained via nasopharyngeal aspiration, can be used to confirm the exact cause, these are usually restricted to research settings.[2] Bacterial infection should be considered if a person does not improve with standard treatment, at which point further investigations may be indicated.[5]

Severity

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Westley score: Classification of croup severity[3][14]
Feature Number of points assigned for this feature
0 1 2 3 4 5
Chest wall
retraction 		None Mild Moderate Severe
Stridor None With
agitation 		At rest
Cyanosis None With
agitation 		At rest
Level of
consciousness 		Normal Disoriented
Air entry Normal Decreased Markedly decreased

The most commonly used system for classifying the severity of croup is the Westley score. It is primarily used for research purposes rather than in clinical practice.[5] It is the sum of points assigned for five factors: level of consciousness, cyanosis, stridor, air entry, and retractions.[5] The points given for each factor is listed in the adjacent table, and the final score ranges from 0 to 17.[14]

  • A total score of ≤ 2 indicates mild croup. The characteristic barking cough and hoarseness may be present, but there is no stridor at rest.[3]
  • A total score of 3–5 is classified as moderate croup. It presents with easily heard stridor, but with few other signs.[3]
  • A total score of 6–11 is severe croup. It also presents with obvious stridor, but also features marked chest wall indrawing.[3]
  • A total score of ≥ 12 indicates impending respiratory failure. The barking cough and stridor may no longer be prominent at this stage.[3]

85% of children presenting to the emergency department have mild disease; severe croup is rare (<1%).[3]

Prevention

[edit]

Croup is contagious during the first few days of the infection.[13] Basic hygiene including hand washing can prevent transmission.[13] There are no vaccines that have been developed to prevent croup,[13] however, many cases of croup have been prevented by immunization for influenza and diphtheria.[5] At one time, croup referred to a diphtherial disease, but with vaccination, diphtheria is now rare in the developed world.[5]

Treatment

[edit]

Most children with croup have mild symptoms and supportive care at home is effective.[13] For children with moderate to severe croup, treatment with corticosteroids and nebulized epinephrine may be suggested. Steroids are given routinely, with epinephrine used in severe cases.[4] Children with oxygen saturation less than 92% should receive oxygen,[5] and those with severe croup may be hospitalized for observation.[12] In very rare severe cases of croup that result in respiratory failure, emergency intubation and ventilation may be required.[15] With treatment, less than 0.2% of children require endotracheal intubation.[14] Since croup is usually a viral disease, antibiotics are not used unless secondary bacterial infection is suspected.[2] The use of cough medicines, which usually contain dextromethorphan or guaifenesin, is also discouraged.[2]

Supportive care

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Supportive care for children with croup includes resting and keeping the child hydrated.[13] Infections that are mild are suggested to be treated at home. Croup is contagious so washing hands is important.[13] Children with croup should generally be kept as calm as possible.[4] Over-the-counter medications for pain and fever may be helpful to keep the child comfortable.[13] There is some evidence that cool or warm mist may be helpful. However, the effectiveness of this approach is not clear.[4][5][13] If the child is showing signs of distress while breathing (inspiratory stridor, working hard to breathe, blue (or blue-ish) coloured lips, or decrease in the level of alertness), immediate medical evaluation by a doctor is required.[13]

Steroids

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Corticosteroids, such as dexamethasone and budesonide, have been shown to improve outcomes in children with all severities of croup, however, the benefits may be delayed.[7] Significant relief may be obtained as early as two hours after administration.[7] While effective when given by injection, or by inhalation, giving the medication by mouth is preferred.[4] A single dose is usually all that is required, and is generally considered to be quite safe.[4] Dexamethasone at doses of 0.15, 0.3 and 0.6 mg/kg appear to be all equally effective.[16]

Epinephrine

[edit]

Moderate to severe croup (for example, in the case of severe stridor) may be improved temporarily with nebulized epinephrine.[4] While epinephrine typically produces a reduction in croup severity within 10–30 minutes, the benefits are short-lived and last for only about 2 hours.[2][4] If the condition remains improved for 2–4 hours after treatment and no other complications arise, the child is typically discharged from the hospital.[2][4] Epinephrine treatment is associated with potential adverse effects (usually related to the dose of epinephrine) including tachycardia, arrhythmias, and hypertension.[15]

Oxygen

[edit]

More severe cases of croup may require treatment with oxygen. If oxygen is needed, "blow-by" administration (holding an oxygen source near the child's face) is recommended, as it causes less agitation than use of a mask.[5]

Other

[edit]

While other treatments for croup have been studied, none has sufficient evidence to support its use. There is tentative evidence that breathing heliox (a mixture of helium and oxygen) to decrease the work of breathing is useful in those with severe disease, however, there is uncertainty in the effectiveness and the potential adverse effects and/or side effects are not well known.[15] In cases of possible secondary bacterial infection, the antibiotics vancomycin and cefotaxime are recommended.[5] In severe cases associated with influenza A or B infections, the antiviral neuraminidase inhibitors may be administered.[5]

Prognosis

[edit]

Viral croup is usually a self-limiting disease,[2] with half of cases resolving in a day and 80% of cases in two days.[6] It can very rarely result in death from respiratory failure and/or cardiac arrest.[2] Symptoms usually improve within two days, but may last for up to seven days.[3] Other uncommon complications include bacterial tracheitis, pneumonia, and pulmonary edema.[3]

Epidemiology

[edit]

Croup affects about 15% of children, and usually presents between the ages of 6 months and 5–6 years.[4][5] It accounts for about 5% of hospital admissions in this population.[3] In rare cases, it may occur in children as young as 3 months and as old as 15 years.[3] Males are affected 50% more frequently than are females, and there is an increased prevalence in autumn.[5]

History

[edit]

The word croup comes from the Early Modern English verb croup, meaning "to cry hoarsely." The noun describing the disease originated in southeastern Scotland and became widespread after Edinburgh physician Francis Home published the 1765 treatise An Inquiry into the Nature, Cause, and Cure of the Croup.[17][18]

Diphtheritic croup has been known since the time of Homer's ancient Greece, and it was not until 1826 that viral croup was differentiated from croup due to diphtheria by Bretonneau.[11][19] Viral croup was then called "faux-croup" by the French and often called "false croup" in English,[20][21] as "croup" or "true croup" then most often referred to the disease caused by the diphtheria bacterium.[22][23] False croup has also been known as pseudo croup or spasmodic croup.[24] Croup due to diphtheria has become nearly unknown in affluent countries in modern times due to the advent of effective immunization.[11][25]

One famous fatality of croup was Napoleon's designated heir, Napoléon Charles Bonaparte. His death in 1807 left Napoleon without an heir and contributed to his decision to divorce from his wife, the Empress Josephine de Beauharnais.[26]

Preston Brooks, a pro-slavery, pre-Civil War US congressman from South Carolina died unexpectedly from a violent attack of croup on January 27, 1857, a few weeks before the March 4 start of the new congressional term to which he had been re-elected.[27]

References

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Croup

View on Grokipedia
from Grokipedia
Croup is a common upper respiratory infection that primarily affects children under 6 years of age, causing and narrowing of the , trachea, and sometimes bronchi, which results in a characteristic barking , inspiratory , hoarseness, and potential breathing difficulties. It typically arises from viral pathogens, most often parainfluenza virus types 1 and 3, with an of 2 to 6 days, and spreads through respiratory droplets or contact with contaminated surfaces. Symptoms usually begin with 1 to 2 days of mild upper respiratory illness, such as a runny or low-grade fever, followed by the abrupt onset of the barking and , which often worsens at night and peaks around days 3 to 4 of illness, lasting 3 to 7 days in total. Epidemiologically, croup impacts approximately 3% of children under 5 years worldwide, with an annual incidence of approximately 3% , showing a higher in boys (1.5:1 ratio) and seasonal peaks in fall and early winter. It is rare in adults and children over due to larger airway diameters, though recurrent or spasmodic forms may occur in those with allergies or underlying conditions. is primarily clinical, using tools like the Westley Croup Score to assess severity based on , retractions, air entry, , and level of consciousness, with scores of ≤2 indicating mild cases suitable for home management, scores of 3-7 indicating moderate disease requiring medical evaluation, and scores ≥8 signaling severe disease often requiring hospitalization. Treatment focuses on reducing airway and supporting ; mild cases are managed at with fluids and acetaminophen for fever, while moderate to severe cases receive a single oral dose of dexamethasone (0.6 mg/kg), which provides faster improvement with many children experiencing relief within a few hours and noticeable reduction in airway swelling and symptoms by 6-12 hours, shortening the overall duration of severe symptoms to 2-4 days though individual responses vary, and, if needed, nebulized racemic epinephrine for rapid symptom relief. Antibiotics are reserved for rare bacterial superinfections, and is required in less than 0.2% of cases. The prognosis is excellent, with most children recovering fully without complications, though severe untreated cases can lead to significant respiratory distress or, rarely, secondary .

Clinical Presentation

Signs and Symptoms

Croup is characterized by a distinctive set of respiratory symptoms primarily affecting the upper airway in young children. The hallmark features include a barking or seal-like , inspiratory —a high-pitched, wheezing sound during —hoarseness of the voice, and varying degrees of respiratory distress. These symptoms arise due to and narrowing of the and trachea, leading to turbulent airflow. Symptoms typically begin 1 to 2 days after the onset of an upper respiratory , such as a , and often intensify at night or in the early morning hours, potentially waking the child from . This nocturnal worsening is attributed to the accumulation of secretions and positional changes that further the airway. The barking may initially be mild but can escalate, becoming more frequent and harsh, especially with agitation or . Associated symptoms commonly include a low-grade fever, coryza (runny or stuffy ), and a hoarse or raspy voice, which may progress to temporary loss of voice in more pronounced cases. In mild presentations, children may exhibit only occasional coughing and during activity or upset, with minimal impact on breathing. Severe cases, however, involve persistent even at rest, visible retractions of the chest or neck muscles, increased respiratory effort, agitation, and in rare instances, (bluish discoloration of the skin due to low oxygen). Croup most frequently occurs in children between 6 months and 3 years of age, with peak incidence around 2 years, as their smaller airways are more susceptible to obstruction from swelling. Infants younger than 6 months or children older than 6 years are less commonly affected.

The differential diagnosis of croup encompasses several conditions that present with upper airway obstruction, , or barking cough in children, necessitating careful clinical differentiation to guide management. Common mimics include , bacterial , , and spasmodic croup, each distinguished by specific historical and examination features. Epiglottitis, classically caused by Haemophilus influenzae type B (now rare due to ), but currently more often due to other bacteria such as streptococci or non-infectious causes, features sudden onset, high fever exceeding 39°C, , , and a muffled voice, with patients adopting a to maintain airway patency; unlike croup's viral , there is no barking cough, and agitation worsens symptoms dramatically. Bacterial tracheitis typically follows a viral illness but progresses with persistent high fever, toxic appearance, purulent secretions, and severe respiratory distress unresponsive to initial therapies like racemic epinephrine, contrasting croup's milder course. Foreign body aspiration presents abruptly with history, unilateral wheezing or , and asymmetric breath sounds, often without fever or , differing from croup's bilateral involvement and gradual onset. Spasmodic croup, a non-infectious variant linked to or reflux, manifests as recurrent nocturnal episodes of and barking cough without fever or toxicity, resolving quickly with supportive care and lacking the infectious etiology of classic croup. A detailed history and are pivotal in distinguishing croup from these mimics; a typical viral upper respiratory with low-grade fever and nocturnal worsening supports croup, while rapid progression or absence of such history raises suspicion for bacterial or mechanical causes. Atypical features warranting further evaluation include high fever greater than 39°C, , tripod positioning, unilateral signs, or failure to improve with standard croup treatments, prompting consideration of urgent or specialist consultation to rule out life-threatening alternatives.
ConditionTypical AgeKey Distinguishing FeaturesHistorical Clues
Epiglottitis3-12 yearsHigh fever, drooling, dysphagia, tripod position, muffled voiceSudden onset, no prodrome
Bacterial Tracheitis<6 yearsToxic appearance, purulent secretions, unresponsive to epinephrineFollows viral illness, rapid worsening
Foreign Body Aspiration<3 yearsUnilateral stridor/wheezing, asymmetric examChoking episode, abrupt onset
Spasmodic Croup6 mo-3 yrNo fever, recurrent nocturnal episodesAtopic history, quick resolution
This table summarizes core differences to facilitate bedside differentiation.

Causes and

Viral Causes

Croup is predominantly caused by viral infections, which account for the vast majority of cases, with parainfluenza viruses being the most common etiologic agents. Parainfluenza viruses (types 1–3) account for approximately 75% of croup cases, with type 1 being the most common, responsible for biennial outbreaks in the fall of odd-numbered years in temperate climates. Types 2 and 3 of parainfluenza virus are also frequently implicated, with type 2 causing sporadic cases year-round and type 3 peaking in spring and early summer. Other viruses associated with croup include (RSV), which is more common in infants and during winter months; A and B viruses, often circulating in winter; adenovirus; , typically seen in late winter to early spring; and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), associated with increased croup incidence during surges as of 2025. These viruses contribute to the remaining cases, with seasonal variations influencing overall —for instance, RSV and drive increased incidence during colder months. Transmission of these viruses occurs primarily through airborne respiratory droplets or direct contact with contaminated secretions, such as during close personal interactions or coughing. The typical ranges from 2 to 6 days following exposure, after which upper airway develops.

Bacterial Causes

Bacterial causes of croup are rare, comprising less than 5% of all cases, and often manifest as secondary infections superimposed on initial viral laryngotracheobronchitis. These superinfections typically involve pathogens such as , , or , which exacerbate the underlying and lead to more severe airway obstruction. Patients with these secondary bacterial infections commonly exhibit higher fever, purulent secretions, and a toxic clinical appearance, distinguishing them from the milder viral forms and indicating a poorer short-term prognosis if untreated. The incidence of such severe bacterial complications remains low, affecting fewer than 1% of croup cases overall and less than 3% of those requiring hospitalization. Primary bacterial etiologies are even less common but include bacterial tracheitis, which can arise independently or as a complication of viral croup, primarily caused by Staphylococcus aureus or group A Streptococcus (Streptococcus pyogenes). This condition involves bacterial invasion of the trachea, resulting in thick, purulent membranes that cause significant respiratory distress, often necessitating intensive care. Additionally, Mycoplasma pneumoniae may produce a mild, croup-like illness in some children, though it rarely leads to the classic stridor and barking cough. Viral predisposition to these bacterial overlays underscores the importance of monitoring for progression in initially viral presentations. Historically, due to was a major primary bacterial cause of croup-like symptoms, frequently termed "membranous croup" in the pre-vaccine era before the . This toxin-producing infection formed pseudomembranes in the and trachea, mimicking viral croup but with higher mortality rates due to airway occlusion and systemic complications. Widespread since the mid-20th century has drastically reduced its incidence in developed countries, rendering it an exceedingly rare contributor today.

Non-infectious Causes

Spasmodic croup, a non-infectious variant, accounts for a minority of cases and is often triggered by allergic reactions or gastroesophageal reflux, leading to acute subglottic without a preceding viral illness. It typically presents suddenly, often at night, with barking and , and may recur in children with atopic conditions.

Pathophysiology

Croup arises from an initial that triggers an inflammatory response in the upper airway, primarily affecting the subglottic region. This leads to a cascade of pathophysiological events characterized by the release of pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α, which promote the recruitment of immune cells including lymphocytes, neutrophils, and histiocytes to the site of . The resulting cellular infiltration and activation cause endothelial damage, loss of ciliary function, and increased in the , , and of the , trachea, and bronchi. This inflammatory process peaks in intensity between 24 and 48 hours post-, with maximal and mucus production exacerbating airway compromise. The hallmark of croup is subglottic , where swelling in the narrow subglottic space—circumscribed by the rigid —dramatically reduces the airway diameter, even a small increase in mucosal thickness can narrow the lumen by up to 75%. and accumulation of viscous further obstruct the airway, creating a fixed partial obstruction that limits and promotes turbulent flow, particularly during inspiration when negative intrathoracic pressure exacerbates the narrowing. This turbulent generates the characteristic inspiratory , a high-pitched sound resulting from vibrations in the edematous subglottic tissues. Radiographic imaging may reveal the "" on anteroposterior neck , a tapered narrowing of the subglottic trachea resembling a church , directly attributable to the circumferential in this region. Overall, these mechanisms culminate in increased and potential if the obstruction progresses, though the process is typically self-limited as the resolves the over several days.

Diagnosis

Clinical Evaluation

The diagnosis of croup is primarily clinical, relying on a characteristic history and to confirm upper airway consistent with viral laryngotracheobronchitis in children, typically aged 6 months to 3 years. Routine or studies are generally unnecessary in typical cases, as the presentation of a barking cough, hoarseness, and inspiratory following a viral strongly supports the . History taking focuses on recent upper respiratory symptoms, such as rhinorrhea, low-grade fever, and cough, which often precede the acute onset of stridor and barking cough by 1 to 2 days. Inquiry into exposure to ill contacts is essential, given the contagious nature of common viral etiologies like parainfluenza. Vaccination status should be reviewed to exclude vaccine-preventable conditions that may mimic croup, such as type b epiglottitis in unvaccinated children. On , reveals inspiratory , a high-pitched sound indicating laryngeal obstruction, often accompanied by a seal-like barking and hoarseness. Assessment of respiratory effort includes evaluation for signs of distress, such as intercostal or subcostal retractions, nasal flaring, , and, in severe cases, or use of accessory muscles. The examination should be performed calmly to avoid agitation, which can exacerbate . Ancillary tests are reserved for cases where the diagnosis is uncertain or mimics are suspected. A lateral neck radiograph may demonstrate the classic "steeple sign" of subglottic narrowing if performed, but it is not routine due to risks and the reliability of clinical findings in typical presentations. Viral testing via is not recommended routinely, as it does not alter management and may distress the child.

Severity Classification

Severity classification in croup is essential for guiding clinical management and determining the appropriate level of care, with the Westley Croup Score serving as the most widely used standardized tool for assessing disease severity in children. This score, originally developed in and validated in subsequent studies, evaluates five key clinical features to provide an objective measure, though it incorporates some subjective assessments. The Westley Croup Score components are as follows:
ComponentScoring Details
Level of consciousnessNormal (including sleep): 0; Disoriented: 5
CyanosisNone: 0; With agitation: 4; At rest: 5
StridorNone: 0; With agitation: 1; At rest: 2
Air entryNormal: 0; Decreased: 1; Markedly decreased: 2
RetractionsNone: 0; Mild: 1; Moderate: 2; Severe: 3
The total score ranges from 0 to 17, with severity categorized as mild (0-2), moderate (3-7), severe (8-11), or impending (12-17). Clinical criteria align with these scores: mild croup typically involves occasional barking , no at rest, and minimal or no retractions, allowing for home management; moderate croup features frequent barking , at rest, and mild to moderate retractions, often requiring medical evaluation; severe croup includes marked retractions, persistent , and signs of distress such as or , necessitating urgent intervention. and retractions, as scored features, are particularly predictive of outcomes in these classifications. In emergency settings, the Westley Croup Score is applied to stratify patients upon presentation and to monitor response to interventions, with reassessment recommended 1-2 hours after treatments to adjust care accordingly. It aids in deciding between outpatient management for mild cases and hospitalization for moderate to severe ones. Limitations of the Westley Croup Score include subjective elements in evaluating retractions, air entry, and agitation levels, which can lead to inter-observer variability; additionally, it is not validated for use in infants under 3 months of age, where croup is uncommon and alternative etiologies predominate.

Treatment

Supportive Care

Supportive care forms the cornerstone of for mild to moderate croup, focusing on alleviating symptoms and promoting recovery without pharmacological intervention. At home, parents are advised to position the child upright, as this posture can facilitate easier by reducing pressure on the airway. Encouraging adequate hydration through oral fluids helps thin secretions and prevents , which may exacerbate respiratory distress. Exposure to cool outdoor air may provide short-term symptom relief, but humidified air from humidifiers is not recommended by current guidelines due to lack of evidence of benefit. In hospital settings, close monitoring of , including and , is essential to assess the child's condition and detect any progression of symptoms. Minimal handling and a calm environment are prioritized to avoid agitation, which can increase oxygen demand and worsen . For airway maintenance, sedatives are avoided due to the risk of respiratory depression in already compromised airways. If the child is not significantly distressed, oral intake is encouraged to maintain hydration and . Evidence supports the low-risk nature of mist therapy despite its limited efficacy; a Cochrane of randomized trials found no significant improvement in croup scores with humidified air compared to controls, but it remains a safe, non-invasive option for comfort. Overall, these measures are particularly effective for mild symptoms, where most children recover within 48 hours with rest and observation.

Corticosteroids

Corticosteroids serve as the cornerstone of pharmacological treatment for croup, primarily by exerting effects that reduce subglottic and mucosal swelling, thereby alleviating airway obstruction associated with the condition's . This mechanism addresses the inflammatory response triggered by viral infection in the and trachea, leading to decreased and improved respiratory effort. Dexamethasone is the preferred , administered as a single dose of 0.6 mg/kg orally, intramuscularly, or intravenously (maximum 10-16 mg), which has been shown to reduce croup symptoms within 6 hours of administration, with benefits observable as early as 30 minutes and noticeable reduction in airway swelling and symptoms by 6-12 hours. The steroid helps shorten the overall severity and duration of symptoms, typically limiting the worst phase to 2-4 days in treated cases, though every child is different, with some recovering quickly and others taking up to a week. This dosing regimen is supported by high-quality demonstrating faster symptom resolution, reduced need for additional interventions, and lower rates of hospital admission or return visits compared to . Some current guidelines recommend corticosteroids even for mild croup to prevent worsening. Alternative agents include oral (1 mg/kg, single dose) or nebulized (2 mg, single dose), which offer comparable efficacy to dexamethasone in moderate croup, though dexamethasone is favored for its longer duration of action and in oral form. Treatment is typically limited to a single dose, as multi-dose regimens do not provide additional benefits and may increase the risk of adverse effects. Current guidelines from the (AAP) and the National Institute for Health and Care Excellence (NICE) recommend corticosteroids for all cases of croup except the mildest, where symptoms may resolve without intervention. Corticosteroids are effective in the majority of cases, with meta-analyses indicating significant symptom improvement in 80-90% of treated children and a of 50% for hospitalization. Side effects are minimal with a single dose, including in less than 5% of patients and transient agitation or hyperactivity in a small subset.

Nebulized Epinephrine

Nebulized epinephrine, often administered as racemic epinephrine, serves as a short-acting intervention for providing temporary relief from severe airway obstruction in croup. It is particularly indicated in cases of moderate to severe disease, such as when patients exhibit at rest or a Westley croup score of 3 or greater. The recommended dosage is 0.5 mL of 2.25% racemic epinephrine diluted in 2.5 mL of normal saline and delivered via . This dose may be repeated every 1 to 2 hours as needed if symptoms persist, under close medical supervision. As an alternative, L-epinephrine (1:1000 solution) can be used at a dose of 0.5 mL/kg, up to a maximum of 5 mL, nebulized in a similar manner, offering comparable when racemic epinephrine is unavailable. The therapeutic effect stems from epinephrine's alpha-adrenergic stimulation, which induces of submucosal arterioles in the upper airway, thereby reducing hydrostatic pressure and in the subglottic region. Symptom improvement, including decreased and improved air entry, typically occurs within 10 to 30 minutes of administration and lasts about 2 hours. Due to the transient nature of this relief, patients receiving nebulized epinephrine require at least 2 to 3 hours of hospital observation to monitor for rebound worsening of symptoms as the vasoconstrictive effects subside. Evidence from randomized controlled trials supports its use in severe croup, demonstrating significant reductions in Westley croup scores by 2 to 3 points within 30 minutes and a decreased need for compared to or supportive care alone. Additionally, it shortens length of stay in moderate to severe cases without increasing the risk of symptom exacerbation post-treatment.

Oxygen Therapy

Oxygen therapy serves as a supportive measure in the management of severe croup, primarily aimed at correcting in children exhibiting significant respiratory distress. It is indicated when (SpO2) falls below 92% or in the presence of marked clinical distress, such as or altered mental status, with the goal of maintaining SpO2 above 94%. is uncommon in typical viral croup, occurring in fewer than 10% of cases, and its presence may prompt evaluation for alternative or complicating diagnoses. Supplemental oxygen is typically delivered as humidified low-flow oxygen at rates sufficient to achieve target saturation, using methods such as a face , , or oxygen hood, which are preferred for their tolerability in young children. High-flow or other advanced systems are reserved for cases where standard delivery fails to maintain adequate oxygenation. Humidification helps prevent drying of the airway mucosa, though evidence for its specific benefit in croup remains limited to general pediatric respiratory support principles. Continuous monitoring with is essential during oxygen administration to assess response and guide weaning, which should occur as clinical symptoms improve and SpO2 stabilizes above 94% in room air. If oxygen therapy fails to resolve despite other interventions, escalation to airway support, including rare (required in less than 1% of hospitalized cases), may be necessary. Overall, oxygen plays a limited but critical role in the subset of severe croup presentations, emphasizing its use only when threatens adequate tissue perfusion.

Other Therapies

Antibiotics are not routinely recommended for the treatment of croup, as the condition is primarily viral in . They are reserved exclusively for cases with suspected secondary bacterial , such as bacterial , where intravenous administration of agents like may be indicated based on clinical suspicion and local resistance patterns. Empiric use in uncomplicated croup has no proven benefit and may contribute to unnecessary risks like . In severe croup refractory to standard therapies, —a of and oxygen—can be considered as an adjunct to reduce and improve through narrowed upper airways. This therapy is particularly useful in moderate to severe cases during emergency transport or when nebulized epinephrine fails to provide relief, with some randomized trials showing comparable symptom improvement to racemic epinephrine alone. However, evidence from systematic reviews remains limited and conflicting, leading to its use only in select severe scenarios rather than as routine care. Intubation and mechanical ventilation represent a last-resort intervention for croup, employed only in the setting of impending or actual despite maximal medical management. This procedure is required in fewer than 2% of hospitalized children with croup, typically for a brief duration until subsides, and carries risks including post-extubation . Close monitoring in a is essential post-intubation to facilitate timely extubation. Emerging antiviral therapies, such as , have been investigated for viral croup but lack sufficient evidence to support routine use. While demonstrates activity against parainfluenza viruses—the most common cause of croup—clinical trials in immunocompromised patients with severe lower respiratory infections show inconsistent efficacy, and it is not recommended for otherwise healthy children due to cost, administration challenges, and potential toxicity. Ongoing research focuses on more targeted antivirals, but current guidelines emphasize supportive and anti-inflammatory measures over antivirals.

Prevention

Hygiene Practices

Hygiene practices play a crucial role in reducing the transmission of viruses that cause croup, primarily through disrupting the spread of respiratory pathogens like human parainfluenza virus. Frequent handwashing with and water for at least 20 seconds is recommended, particularly after contact with potentially contaminated surfaces or individuals, as it effectively removes germs from the hands. If and water are unavailable, using an alcohol-based containing at least 60% alcohol provides a suitable alternative. These measures are especially important in settings like childcare facilities where close contact among children increases transmission risk. To further limit exposure, caregivers should encourage avoiding crowded indoor spaces during peak croup seasons, which typically occur in the fall and early winter when viral activity surges. Isolating children who are ill by keeping them home from school or daycare until symptoms resolve helps prevent the spread to others, as infected individuals can transmit the through respiratory droplets. Additionally, children to cover their coughs and sneezes with a tissue or the crook of their elbow, followed by proper disposal of tissues, reinforces respiratory etiquette. Environmental hygiene measures complement personal practices by targeting fomites that harbor viruses. Routinely cleaning and disinfecting frequently touched surfaces and toys with and detergent-based cleaners reduces viral contamination in homes and childcare settings. Avoiding exposure to tobacco smoke is also essential, as irritates the airways and increases susceptibility to respiratory infections, thereby heightening the risk of croup development or worsening. Overall, adherence to these hygiene strategies can reduce the spread of respiratory viruses by approximately 20%, according to CDC analyses of infection prevention .

Vaccination

Vaccination plays an indirect role in preventing croup by targeting specific viral and bacterial pathogens that can cause or mimic the condition, thereby reducing overall incidence among children. Although most cases of croup are caused by parainfluenza viruses for which no vaccine exists, immunizations against , , and type b (Hib) have demonstrably lowered the occurrence of pathogen-specific croup or similar laryngotracheobronchitis presentations. As of 2025, no parainfluenza vaccines are approved, with candidates still in preclinical or early clinical stages. The annual is recommended for all children aged 6 months and older, with two doses required for first-time recipients under 9 years to establish immunity. This vaccination significantly reduces the risk of infection, which causes a small proportion (approximately 5%) of croup cases, particularly during seasonal outbreaks; studies indicate it can prevent 40-60% of influenza-related illnesses in healthy children, based on recent seasons. Diphtheria vaccination, administered as part of the DTaP (diphtheria, , and acellular pertussis) series starting at 2 months of age with boosters through , effectively prevents diphtheritic croup, a severe bacterial form characterized by pseudomembrane formation in the . Widespread DTaP has reduced diphtheria incidence by over 99% in vaccinated populations since its introduction, virtually eliminating diphtheritic croup in regions with high coverage rates above 90%. The Hib conjugate vaccine, given in a series beginning at 2 months with boosters at 12-15 months, protects against invasive type b infections, including bacterial that can present with croup-like symptoms such as and . Prior to routine Hib in the late 1980s, Hib was a leading cause of such bacterial supraglottic infections in children under 5 years; post-vaccination, invasive Hib disease has declined by more than 99% , correspondingly reducing these croup mimics. Despite these benefits, limitations persist: there is no available for parainfluenza viruses, the primary cause of viral croup. Additionally, suboptimal uptake—such as influenza coverage rates at approximately 49% among U.S. children under 5 years as of the 2024-2025 season—can sustain preventable cases, underscoring the need for improved adherence to maximize croup prevention.

Prognosis and Complications

Prognosis

Croup is typically a self-limiting viral infection in children, with symptoms peaking around 24 to 48 hours after onset and resolving within 3 to 7 days in most cases. Mild cases often improve spontaneously at home with supportive measures, while severe symptoms may peak later, on days 3 or 4. The for croup is exceedingly rare with proper management, less than 0.5% even among intubated patients under modern care, though it can be higher in untreated cases of bacterial complicating the condition. Recurrence occurs in approximately 5% of children, who experience more than one episode, but the long-term prognosis remains excellent with full recovery expected in uncomplicated cases. Favorable outcomes are influenced by several factors, including early administration of corticosteroids like dexamethasone, which accelerates recovery and reduces symptom severity, with many children starting to feel better within a few hours and experiencing noticeable reduction in airway swelling and symptoms by 6-12 hours or sooner. This treatment helps shorten the overall severity and duration of symptoms, often limiting the worst phase to 2-4 days in treated cases, though every child is different, with some recovering quickly and others taking closer to a week. Children under 1 year of age tend to have more severe disease due to smaller airways, increasing the risk of hospitalization.

Complications

While most cases of croup resolve without long-term effects, complications are uncommon, occurring in less than 5% of hospitalized cases, particularly in severe or untreated instances. Respiratory complications include severe airway obstruction leading to respiratory distress, which may require oxygen therapy or ; in infants, this can precipitate apnea, characterized by pauses in breathing due to airway obstruction and fatigue. Secondary bacterial infections such as bacterial , which presents with persistent high fever, toxic appearance, and thick purulent secretions, often requiring antibiotics and potential , or as a bacterial , leading to lower respiratory involvement and increased hospitalization risk. Pulmonary edema, resulting from fluid accumulation in the lungs due to obstructed airflow, is a rare complication. is another infrequent complication, resulting from reduced oral intake amid respiratory distress, coughing, difficulty swallowing, or increased respiratory effort, which may require intravenous fluids for rehydration. Rare but serious outcomes encompass respiratory failure necessitating endotracheal , occurring in approximately 0.5% to 2% of hospitalized children, with even lower rates overall due to effective medical . Additional rare issues include pneumomediastinum, pneumothorax, and otitis media. Long-term sequelae are uncommon but include recurrent croup, which affects up to 60% of children with multiple episodes and is associated with , where acid reflux irritates the airway, or allergies and , predisposing to airway hyperreactivity. Post-intubation , a narrowing of the airway below the , can occur in cases requiring , with risk increasing with duration and tube size mismatch. Risk factors for complications include delayed treatment, which allows progression to severe obstruction and hypoxia, and underlying conditions such as , which heighten susceptibility to secondary infections and prolonged recovery.

Epidemiology

Incidence and Prevalence

Croup is a common acute respiratory condition primarily affecting young children, with a global annual incidence estimated at 3% among those under 5 years of age, or approximately 532 cases per 100,000 individuals. In certain regions, such as , the lifetime risk reaches about 15%, meaning a substantial proportion of children experience at least one episode before school age. The condition peaks in incidence between 6 months and 3 years of age, reflecting vulnerability in this developmental stage. Only a small fraction of croup cases require hospitalization, typically 1% to 5% of diagnosed episodes, as most are mild and resolve with supportive care. , pre-2020 data indicate around 40,000 annual hospitalizations for croup among children, highlighting its role in care despite low severity in the majority of instances. Epidemiological trends for croup have remained relatively stable over decades, though non-SARS-CoV-2 viral cases declined substantially during the early (March to September 2020) due to widespread masking, , and reduced transmission of common respiratory pathogens. Cases resurged post-2020, with notable increases in COVID-19-associated croup during the Omicron variant wave in late 2021 to early 2022; by 2024-2025, incidence had largely stabilized to pre-pandemic levels in many regions. True prevalence may be underestimated, as up to 85% of cases are mild and often managed at home without formal medical evaluation or reporting.

Demographic Patterns

Croup predominantly affects young children, with the majority of cases occurring between 6 months and 6 years of age and peak incidence in the second year of life; it is rare in due to the larger diameter of the adult airway. Males are affected 1.5 times more often than females, a pattern observed across multiple studies and potentially linked to anatomical differences in airway size. Seasonal patterns show peaks in autumn, driven by human parainfluenza virus type 1 outbreaks, with additional surges in spring-summer from type 3; incidence rises substantially during cooler months overall, reflecting increased indoor crowding and viral transmission. Risk factors include male sex, young age, and previous episodes of croup; attendance at daycare may increase exposure to respiratory viruses, while low is associated with higher rates due to crowding and limited preventive care. has been linked to increased respiratory infections in children but evidence for a specific association with croup is limited.

History

Early Descriptions

The term "croup" originated in the Scottish dialect, referring to "to cry hoarsely," and was first applied to the disease in medical literature by Francis Home in his 1765 treatise, An into the Nature, Cause and Cure of the Croup, where he described 12 cases of the illness characterized by inflammation of the and trachea in children. Home's work marked the initial systematic recognition of croup as a distinct entity, distinguishing it from other respiratory conditions like angina trachealis, though he attributed it to a contagious principle without identifying its cause. In the early 19th century, Irish physician John Cheyne provided one of the earliest detailed clinical descriptions of croup's hallmark symptoms in his 1813 publication, An Essay on Cynanche Trachealis, or Croup, noting the "deep barking cough" accompanied by and respiratory distress, often following a catarrhal . Cheyne emphasized the disease's rapid progression and high mortality in young children, based on observations from epidemics, and proposed it involved membranous of the airways, though he could not pinpoint the . By the mid-19th century, French physician Pierre Bretonneau advanced the understanding of croup by differentiating it from in his 1826 treatise Des inflammations spéciales du tissu muqueux, coining the term "diphthérite" for the bacterial form (true croup) characterized by pseudomembranes, while describing non-diphtheritic cases as "false croup" due to their lack of such membranes and different clinical course. This distinction was crucial, as it separated infectious laryngotracheitis from the more severe diphtherial involvement, though both were still viewed broadly as contagious without knowledge of specific pathogens. Early observers, including and Cheyne, recognized croup as infectious based on its patterns and familial clustering, yet the precise remained elusive until the mid-20th century, when viruses such as parainfluenza were identified as primary causes through isolation studies in the 1950s. This gap led to misconceptions that lumped croup with various laryngeal inflammations, delaying targeted interventions until viral agents were confirmed.

Development of Treatments

In the 19th and early 20th centuries, management of severe croup primarily relied on as a last-resort intervention to secure the airway, particularly in cases linked to diphtherial obstruction, though it carried high risks and mortality rates exceeding 50% in some series. Steam inhalation emerged as a common non-invasive treatment around the late , inspired by anecdotal observations of symptom relief from moist air, but subsequent randomized trials in the demonstrated its lack of efficacy beyond effects. By the mid-20th century, antibiotics were routinely administered when bacterial etiologies like or were suspected, reflecting the era's limited understanding of viral predominance in croup cases, though their use declined with improved diagnostics and . Additionally, routine against type b (Hib) since the 1990s and has virtually eliminated bacterial and diphtheritic croup, further reducing severe airway obstructions. Corticosteroids were first introduced for croup in the 1960s, initially via intramuscular or intravenous routes to reduce airway , marking a shift toward pharmacological approaches despite early controversy over efficacy and side effects. From the 1980s onward, evidence-based advancements solidified use, with a pivotal 1989 confirming dexamethasone's benefits in reducing symptom severity and hospitalization needs in moderate to severe cases. Concurrently, nebulized epinephrine was standardized as an adjunct for acute distress, following trials in the late 1970s and that showed transient vasoconstrictive relief of upper airway , typically lasting 1-2 hours and enabling safer observation. In recent decades, recommendations from the (AAP), as outlined in a 2001 review and reinforced in subsequent publications through the 2020s, have emphasized a single oral dose of dexamethasone (0.15-0.6 mg/kg) as first-line therapy for all severity levels of croup, leading to dramatic reductions in and rates compared to pre-steroid eras. This approach has minimized invasive interventions, with now required in less than 0.2% of cases overall.

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