THE PRESENCE OF LATEX CAN INDUCE FALSE-POSITIVE SKIN-TESTS IN SUBJECTS TESTED WITH PENICILLIN DETERMINANTS

Latex allergens are ubiquitous, and exposure may occur from different sources in the medical environment and in daily life. The observation that subjects with latex allergy were skin test positive to major and minor determinants of penicillins led our group to carry out an invest igation to try to explain these findings. A group of 20 subjects with a history of allergy to latex and with positive skin tests for, but go od tolerance of, penicillins was studied. The presence of latex contam inants was studied by RAST and RAST inhibition. Sixteen of the subject s were positive to at least one of the penicillin determinants used, a nd 14 (87%) of these were positive to at least two determinants. Repet ition of skin tests using the container without a stopper changed the skin test results to negative in almost all cases, indicating that som e trace contaminants had still been present. RAST-inhibition studies s howed that in all penicillin determinants there were trace amounts of latex allergens varying between 3 and 0.03 mu g/ml. These results indi cate that skin tests with penicillin in subjects allergic to latex may give false-positive results and lead to such patients being falsely d iagnosed as allergic to betalactams when penicillins are stored in con tainers with rubber stoppers.