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To the Editor:—
The first reports on allergic phenomena uniformly stressed that sensitization produces a state without protection (anaphylaxis) against minimal amounts of the antigen. Testing procedures for the detection of allergies are only reliable when carried out with minimal amounts of the allergen.This rule is of utmost importance when testing with anaphylactoid substances. Intracutaneous or epicutaneous applications of such substances in higher amounts might easily produce anaphylactoid inflammation which is indistinguishable from true allergic inflammation.In "Allergy to Dermatologic Agents" (198:517, 1966), it was claimed that patch tests for neomycin allergy should be performed with 20% to 40% solutions. Even though the exact amount of solution for the testing procedure is not mentioned, one might assume that an amount of 50 to 200 mg of neomycin is applied on skin areas with greatly enhanced penetration. Studying the table in the paper, one finds the number of "allergic"
Raab WP. Allergic and Anaphylactoid Inflammation. JAMA. 1967;201(2):143-144. doi:10.1001/jama.1967.03130020089035