First of all, it's important to obtain a detailed history. If the urticaria and angioedema arise infrequently, look for possible triggers such as foods, drugs, exercise or physical factors. If the outbreak on the skin is chronic and persistent, occurring daily for more than six weeks, you're often dealing with chronic idiopathic urticaria. This may be the result of an autoantibody directed against a protein or immunoglobulin IgE on mast cells. Treatment is symptomatic until the autoantibody disappears.

Be careful to check any medications that were taken prior to the onset of angioedema or that are used on a regular basis. For instance, angiotensin-converting enzyme inhibitors can cause this condition by preventing the breakdown of bradykinin -- even if the patient has been taking the agent uneventfully for several years.

A rare disease, hereditary angioedema, is transmitted in an autosomal dominant fashion. It typically causes nonpruritic angioedema following trauma, stress, infection or for no apparent reason. Diagnosis is important, as this condition can be treated with C1 esterase inhibitor concentrate. PK