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To the Editor.—
Dr. Epstein's letter calls attention to an important question: What factor explains a 22.2% incidence of positive patch test reactions to mercury bichloride? In our article, we stressed that most of the reactions elicited in our selected group of patients were of low intensity, and that patients with such mild reactions probably were not "clinically" sensitive. In view of the low (0.05%) concentration of mercury bichloride used in our tests (rather than the standard 0.1% concentration), we considered it unlikely that the reactions were due to primary irritant effects. Dr. Epstein, on the other hand, favor the latter possibility.Black, MD, in Auckland, New Zealand (written communication, Sept 5, 1973), found that, of 25 contact allergens tested, mercuric chloride in a 0.1% concentration elicited the highest percentage (14%) of reactions among his 215 patients. However, in only one of the 30 positively reacting patients was there a
Rudolf L. Baer, David R. Ramsay. Mercury Allergy and Patch Testing-Reply. Arch Dermatol. 1974;109(1):98–99. doi:10.1001/archderm.1974.01630010070027