Chronic spontaneous urticaria (CSU), also known as chronic idiopathic urticaria (CIU), is defined by the presence of wheals, angioedema, or both for more than six weeks. The most common symptoms of chronic spontaneous urticaria are angioedema and hives that are accompanied by itchiness.

Chronic spontaneous urticaria, despite its cause being unknown, is linked to a higher prevalence of autoimmune diseases, and is often worsened by triggers like stress, infections, certain foods, or nonsteroidal anti-inflammatory drugs. The hives and angioedema seen in CSU is thought to be linked to the degranulation of skin mast cells. Mast cells release proteases, histamine, cytokines, and arachidonic acid metabolites, causing swelling, redness, and itching.

The standard workup for CSU differs in different parts of the world. However, most doctors agree on the importance of having a detailed history. The main goal is to identify any urticaria-inducing factors because eliminating them is the most straightforward course of treatment. Basic laboratory tests, such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and possibly a complete blood count (CBC) with differential, are critical for detecting signs of systemic inflammation and ruling out autoinflammatory conditions as well as urticarial vasculitis with systemic involvement.

For the treatment of chronic spontaneous urticaria, a two-pronged strategy has been proposed. The underlying cause(s) and/or eliciting trigger(s) must first be identified and eliminated. The second approach is pharmacotherapy, which aims to alleviate symptoms. A therapeutic approach should be implemented in three steps, according to current guidelines: (1) taking a second-generation antihistamine once daily; (2) increasing the second-generation antihistamine's daily dose up to four times; and (3) pursuing off-label therapy with cyclosporine A or montelukast or add-on therapy with omalizumab, which is an approved treatment option for CSU.

Angioedema, excruciatingly itchy recurrent wheals, or both can be signs of chronic spontaneous urticaria. Between 40 and 50 percent of CSU patients experience angioedema. However, angioedema is the main symptom reported by about 10% of patients.

Usually, urticarial lesions or hives are elevated, erythematous plaques with a defined perimeter. If a patient is taking antihistamines, these lesions may appear flattened and take on a range of sizes. It can affect any part of the body, including parts where clothing might press against the skin. Lesions typically do not last more than 24 hours. The degree of pruritus can interfere with everyday activities and sleep.

Angioedema is characterized by sporadic, asymmetrical submucosal or subcutaneous edema. It is more common to experience paresthesia, such as tingling or numbness, than the pruritus associated with urticaria. Often affected body parts are the lips, eyes, cheeks, and limbs. Urticaria and angioedema typically coexist, but in a small percentage of cases, angioedema may be the only symptom.

While the cause of chronic spontaneous urticaria is unknown many individuals with chronic urticaria have been found to have a higher prevalence of various autoimmune diseases. Many patients with chronic spontaneous urticaria report that certain triggers, like stress, infections, certain foods, or nonsteroidal anti-inflammatory drug consumption, cause their disease to worsen.