The theory of the patch test was original with Jadassohn,1 but the method did not come into general use until 1929, when Bloch2 published a description of the technic. In the United States, Sulzberger and his associates3 have made it the basis of much study. The test is considered to be of definite value to dermatologists in the investigation of dermatitis due to contact with industrial materials, especially cosmetics, textiles and a variety of chemicals. The technics now commonly in use were developed in order to determine the reactivity of the skin to a substance held in contact with it over a given period. The substance to be tested is placed on the skin and covered by rubber tissue or cellophane, and this in turn is strapped tightly to the skin with adhesive plaster. A modification of the usual method was used by Hansen4 in Copenhagen,