Signs and symptoms

Signs and symptoms are diagnostic indications of an illness, injury, or condition. While signs are objective and externally observable; symptoms are a person's reported subjective experiences.

A sign, for example, can be an elevated or lower than normal temperature or blood pressure; or an abnormal finding showing on medical imaging. A symptom is something out of the ordinary that is experienced by an individual such as feeling feverish, a headache or other pains in the body. Symptoms can be a result of the immune system's response to an infection, the physical manifestation of an abnormal body condition, or the effect of a consumed substance. Symptoms, though often indicative of a disease process, are not always diagnostically relevant, and can be idiopathic in nature.

A medical sign is an objective observable indication of a disease, injury, or medical condition that may be detected during a physical examination. These signs may be visible, such as a rash or bruise, or otherwise detectable such as by using a stethoscope or taking blood pressure. Medical signs, along with symptoms, help in forming a diagnosis. Some examples of signs are nail clubbing of either the fingernails or toenails or an abnormal gait.

A symptom is something felt or experienced, such as pain or dizziness. Signs and symptoms are not mutually exclusive, for example a subjective feeling of fever can be noted as sign by using a thermometer that registers a high reading. The CDC lists various diseases by their signs and symptoms such as for measles which includes a high fever, conjunctivitis, and cough, followed a few days later by the measles rash.

Cardinal signs and symptoms are very specific even to the point of being pathognomonic. A cardinal sign or cardinal symptom can also refer to the major sign or symptom of a disease. Abnormal reflexes can indicate problems with the nervous system. Signs and symptoms are also applied to physiological states outside the context of disease, as for example when referring to the signs and symptoms of pregnancy, or the symptoms of dehydration. Sometimes a disease may be present without showing any signs or symptoms when it is known as being asymptomatic. The disorder may be discovered through tests including scans. An infection may be asymptomatic but still be transmissible.

Signs and symptoms are often non-specific, but some combinations can be suggestive of certain diagnoses, helping to narrow down what may be wrong. A particular set of characteristic signs and symptoms that may be associated with a disorder is known as a syndrome.

When a disease is evidenced by symptoms it is known as symptomatic. There are many conditions including subclinical infections that display no symptoms, and these are termed asymptomatic.

Signs and symptoms may be mild or severe, brief or longer-lasting when they may become reduced (remission), or then recur (relapse or recrudescence) known as a flare-up. A flare-up may show more severe symptoms.