Urticaria and Angioedema

Excerpt

Urticaria consists of discrete areas of skin edema that are usually pruritic. Angioedema, which involves the deeper dermis and subcutaneous tissue, presents as localized areas of soft tissue swelling. Urticarial lesions are initially erythematous but often progress with central clearing to give a typical wheal and flare appearance. These lesions can vary from a few millimeters to several centimeters in diameter and may have serpiginous or polycyclic borders. Although most commonly involving the trunk and proximal extremities, the lesions can occur anywhere and are particularly common in areas of tight-fitting clothing. The lesions of angioedema are seldom pruritic but can produce an uncomfortable burning sensation and sometimes pain. Angioedema is most common in the loose tissues around the eyes and mouth. Urticaria and angioedema occur together in 49% of patients, urticaria is seen alone in 40%, and angioedema occurs alone in 11% of cases.

Urticaria is defined as chronic when lesions occur continuously or intermittently for longer than 6 weeks; although somewhat arbitrary, this definition of chronicity is clinically useful. Lesions of chronic urticaria usually last several hours and disappear in one area only to reappear in another.