Physical allergies and exercise. Clinical implications for those engaged in sports activities.

There are several allergic responses that may occur in susceptible individuals as a result of exposure to physical stimuli. Most of these conditions are mediated by vasoactive substances and usually result in symptoms of urticaria and/or angioedema. There are 2 such conditions that may occur as a direct result from exercise. The first of these is cholinergic urticaria. Patients with cholinergic urticaria experience punctate (2 to 4mm) hives which occur reproducibly with exercise or with passive warming, such as might occur in a steam bath or hot pool. Life-threatening hypotension or angioedema usually do not occur with cholinergic urticaria. This condition usually responds well to oral hydroxyzine. Exercise-induced anaphylaxis (EIA) is a form of physical allergy that has been recognised with increasing frequency in recent years. This syndrome typically presents with generalised pruritus, a flushing sensation, a feeling of warmth and the development of conventional (10 to 15mm) urticaria in association with vigorous physical exertion only. Symptoms tend to occur variably with exposure to exercise and do not typically occur with passive warming. During symptomatic attacks, cutaneous mast cells degranulate and serum histamine levels increase. Treatment is problematic. Cessation of exercise with onset of symptoms and self-administration of epinephrine (adrenaline) are recommended. Other physical allergies that may affect exercising individuals include cold urticaria, localised heat urticaria, symptomatic dermatographism (dermographism), delayed pressure urticaria (angioedema), solar urticaria and aquagenic urticaria. Management of these conditions may include patient education, selective avoidance, antihistamines and, in some cases, induction of tolerance.