The angry back syndrome: eczema creates eczema.

False positive patch test reactions are common when the skin of the back is hper-reactive. Such reactions can obscure or invalidate observations of multiple specific sensitivity and of cross-sensitivity to contactants. The pathogenesis of the hyper-reactive skin ('angry back') is discussed and a mechanism postulated for the notion that eczema at certain sites can provoke an eczematous tendency at other sites.