In the modern practice of Allergy, it is occasionally necessary or convenient to perform routine diagnostic skin testing while the patient is taking antihistamines. Current texts contain general statements that antihistamines depress skin reactions, but no quantitative data are given. Present concepts are based on work done with antigen challenge in sites locally injected with Pyribenzamine or Benadryl. A double blind study was designed to evaluate the effect of oral doses of antihistamine within the currently accepted therapeutic range. The patients studied included both reactors and nonreactors. The antihistamine utilized was Pyribenzamine, and a placebo was obtained for the fifty milligram tablet. Over seventy-five patients were challenged with two sets of ten intradermal injections, and results were tabulated before the double blind code was broken. This study indicated the need for further study in the range of nonreactors and very strong reactors. Analysis demonstrated no significant effect of antihistamine on intradermal wheals. Antihistamines may be used to suppress systemic effects of antigen challenge, while skin reactions serve as a guide to hyposensitization therapy.
Billingsley, James Glazebrook, "A Study of the Effect of Antihistamine on Clinical Allergy Skin Testing" (1960). University Libraries Digitized Theses 189x-20xx. 121.