AMONG the first and classical allergic - sensitizations studied were those due to topically applied medicaments (Jadassohn1 ). As a matter of fact, since many topical medicaments are "simple" chemicals, some of these allergic sensitizations have been investigated in considerable detail from the viewpoint of the specific chemical groupings on which the allergenic effects are based (Bloch,2 R. L. Mayer,3 and others). While it had been known that topical medicaments could be the cause of allergic eczematous contact dermatitis, the more or less routine and systematic search for allergenic topical medicaments as causal or contributory factors in allergic contact dermatitis and other eruptions was first suggested by Sulzberger and Goodman.4 They proposed that patients who on the basis of clinical evidence were suspected of having developed allergic hypersensitivity to one or more topical medicaments be subjected to patch tests with a "therapeutic tray," i. e., a