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 lo major and minor to explain these findings. A group of 20 subjects with a history of allergy to latex and with positive skin tests for, but good tolerance of, penicillins was studied. The presence of latex contaminants was studied by RAST and RAST inhibition. Sixteen of the subjects were positive lo at least one of the penicillin determinants used, and 14 (87%) of these were positive to at least two determinants. Repetition of skin tests using the container without a stopper changed the skin test results lo negative in almost all cases, indicating that some trace contaminants had still been present RAST‐inhibition studies showed that in all penicillin determinants there were trace amounts of latex allergens varying between 3 and 0.03 μg/ml. These results indicate that skin tests with penicillin in subjects allergic to latex may give false‐positive results and lead to such patients being falsely diagnosed as allergic to betalactams when penicillins are stored in containers with rubber stoppers.