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February 12, 1968

Testing Neomycin Contact Sensitivity

Author Affiliations

Madison, Wis

JAMA. 1968;203(7):525-526. doi:10.1001/jama.1968.03140070081027

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To the Editor:—  In a letter (201: 143, 1967), Dr. Wolfgang P. Raab questioned the diagnostic value of positive results of patch and intradermal tests done with the concentrations now used to prove neomycin allergy. His conclusions were based on an extrapolation of the results of animal experiments; namely, that guinea pigs, rats, and mice show anaphylactoid (ie, toxic, immediate-type) reactions to intracutaneous injections of 0.1 ml of a 1% neomycin solution.I am aware that intradermal injections of neomycin solutions of this concentration also produce a wheal with a flare in both allergic and nonallergic humans. This type of reaction, however, is not diagnostic of neomycin contact sensitivity. Dr. Raab has confused the issue. It is the delayed eczematous response to tests, not the immediate whealing reaction, that is characteristic of contact sensitivity.Some drugs, apparently "histamine releasers," may cause papular delayed reactions. Intradermal injections of 0.1 ml of