Patch testing in occupational hand dermatitis.

Patch testing is valuable for the management of most forms of hand eczema; it tends to be diagnostically useful, however, only in the nonendogenous forms. Historical and morphologic clues that distinguish hand eczema of endogenous from that of exogenous causes can increase the yield of valuable information from patch testing. Knowledge of the occupations at risk for skin disease and the time required for irritant and allergic contact dermatitis to develop will improve history taking--the key to suspecting an occupational component.