Reduction of Antigen Exposure Time in Patch Tests To 24 Hours.

Results of patch tests obtained with 24 hour and 48 hour occlusion periods using antigen impregnated-discs' (AID) and antigen-containing-saucers(ACS) were studied in 168 patients. Of the 411 patches appr, 4 the results in 400 (97.3210/o) patch tests were concordant (91 positive and 309 negative reactions with both the 24 hour and the 48 hour occlusions tests), while 10 patch test reactions were positive only with 48 hour occlusion, and 1 patch test reaction were positive only With 24 hour occlusion. Of the 91 patch test reactions positive with both the 24 hour and the 48 hour occlusion tests, 81 patch test reactions were equally severe, while 10 patch test reactions were stronger with the 48 hour occlusion test. The discordant reactions were obtained with Lantana camera (3), inerium variabilis (4), Allium cepa (1), and potassium dichromate. (1), while concordant results were found with Parthenium hysterophorus, Calotropis procera, Argemone me)acana, nitrofurazone, neomycin, nickel sulphate an paraphenyl-nediamine. The discordant reactions were obtained almost equally in the summer, winter and rainy seasons.