Follicular dermographism.

Four patients who complained of an inexplicable pruritus of several weeks to several years in duration are presented. General medical studies were unremarkable and the skin was normal except for erythematous papular lesions at sites recently scratched. The skin changes could be reproduced by multiple firm strokes with the broad edge of a tongue blade. The transitory, discrete, follicular, urticarial papules so elicited have been labeled by us as follicular dermographism. It is an entity to be distinguished from cholinergic and aquagenic urticaria. We postulate that follicular dermographism occurs during periods of transient antigenemia. At such times, the frictional force of scratching or the tongue blade test releases antigen from the blood stream to trigger focal urticaria at sites of high density mast cells, namely around the hair follicle. Hydroxyzine is an effective therapy.