Exercise-induced anaphylaxis and urticaria.

Physical exercise is a stimulus capable of provoking urticaria and anaphylaxis in certain individuals. The cutaneous manifestations of EIA include erythema, pruritus, and urticarial whealing. Symptoms may also progress to angioedema, laryngeal edema, bronchospasm, and hypotension. Attacks are consistently associated with increases in serum histamine levels, and atopic individuals are more commonly affected. At least two distinct diseases cause EIA, including CU and classic EIA. A variant form of EIA may also exist. CU episodes are induced by increases in body temperature occurring secondary to physical exercise or passive body warming. Classic EIA episodes are induced only by exercise. Further differences between these two disorders include the size of skin lesions and the high frequency of progression to upper airway distress and shock in classic EIA. The manifestations of EIA occur as a result of mast cell degranulation that releases histamine and other mediators into the circulation. An exaggerated cholinergic response to body warming seems to provoke mast cell degranulation in individuals with CU. In classic EIA, exercise acts as a physical stimulus, which through an unknown mechanism provokes mast cell degranulation. The treatment of acute episodes of EIA includes administration of epinephrine and antihistamines, airway maintenance, and cardiovascular support. Prophylactic treatment includes exercise avoidance, abstention from coprecipitating foods and medications, pretreatment with antihistamines and cromolyn, and the induction of tolerance through regular exercise.