Drug-induced exanthemata : a source of clinical and intellectual confusion

Drug rashes are a common problem occurring in patients across the whole spectrum of medical specialties. They are a source of confusion not only to the wider medical community but even among dermatologists there is lack of clarity about how to describe, classify and approach them. Common patterns of drug rash, apart from the "classical" maculo-papular eruptions (MPE), include urticarial wheals and urticaria-like rashes which it is important to distinguish, because of differences in pathogenetic mechanisms, therapeutic response and prognostic significance. The purpose of this article is to try to offer some structure both from the point of view of clinical classification and also of underlying mechanisms.