By Gary M. White, MD
Cholinergic urticaria is a rare variant of urticaria in which thousands of small urticarial papules develop after sweating. This may be from physical exercise or passive warming.
1-4 mm urticarial papules that may be nearly confluent, giving the skin a peau d'orange appearance, is typical. Onset is within minutes of exercising. Often the patient presents with a suggestive history but no lesions. In such a case, the patient may be asked to exercise in the office or nearby (e.g. jumping jacks, climb stairs) in order to induce the lesions. Alternatively, he/she may make a return appt. and exercise just before.
Postprandial or food-dependent exercise induced anaphylaxis: There are several types of exercise-induced urticarias/anaphylaxis, some of which are induced by certain foods followed by exercise and some by any food followed by exercise. Exercise-induced anaphylaxis and cholinergic urticaria can be differentiated on the basis of urticarial morphology, reproducibility, progression to anaphylaxis and response to passive warming.
The standard antihistamines should be tried although they may not be as effective as in typical urticaria.
In one double-blind study [Derm 1996;193;324], cetirizine 20 mg/day was significantly more effective than placebo at reducing wheals, erythema and pruritus. Periactin (e.g. 4 mg TID) has been reported helpful in the past although significant sedation may occur. One patient of mine experienced significant relief with doxepin 25 mg QHS and cetirizine (10 mg QAM and 10 mg each afternoon).
Many patients do not get significant relief from antihistamines. In such case, sweating may be kept to a minimum. Alternatively, a trial of frequent exercise/sweating to reduce symptoms may be tried.
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