Urticaria is a skin reaction sometimes attributable to allergic phenomena as a result of various immune and inflammatory processes. It manifests as wheals and reddish swellings similar to mosquito bites. Urticaria is accompanied by local swelling (oedema) in some area of the body, though it does not usually leave sequelae.

There are two types of urticaria: acute urticaria, which lasts for hours or days, and chronic urticaria, which evolves over periods of more than three months.

Urticaria has many underlying causes, including the ingestion of foodstuffs or drugs, and insect bites. Treatment is only preventive with the prescription of antihistamines once the clinical condition has developed.

Angioedema is a frequent phenomenon in urticaria, and may present either in isolation or in combination with the latter. It manifests as more or less localised swelling (oedema), as in urticaria. Patients with angioedema suffer pain with practically no itching and with a sensation of skin or mucosal membrane distension. Additional symptoms depend on the location involved and comprise swallowing difficulties if the edema affects the uvula or breathing difficulties if swelling affects the glottis (throat), etc. In most cases, there is no topical reddening as in the case of urticaria.