Antibiotics are Top Contact Allergens Among Medications


By Kerry Wachter, Skin & Allergy News

SAN DIEGO – Antibiotics are the greatest contributor to allergic contact dermatitis among topical medications, according to a retrospective study of 100 patients.

“Neomycin and bacitracin are the worst offenders,” said Dr. Shanna Spring, who presented the study at the annual meeting of the American Contact Dermatitis Society.

The most common positive patch test was for bacitracin (44 tests), followed by neomycin (29) and tixocortol-21-pivalate (19). Notably, 14% of individuals tested positive for both neomycin and bacitracin.

The researchers conducted a retrospective file review from the Ottawa Patch Test Clinic between January 2000 and September 2010. They randomly selected 100 patient files from the “interesting case database” compiled by the clinic staff.

Patients were eligible for the study if they had at least one positive patch test result to a topical medication; those whose patch test read as an irritant, macular erythema, or equivocal were excluded. Three-quarter of patients (74%) were older than 40 years, 68% were female and 34% were atopic, said Dr. Spring of the University of Ottawa.

The researchers were able to identify present relevant sensitizers in 80 patients. The most common sensitizers were antibiotics (59 patients), followed by steroids (31), anesthetics (6) and antifungals (6).

Most patients (64) had only one positive patch test; 20 had two positive tests. Eight patients had five positive patch tests.

In terms of co-reactions, 14 patients had more than one positive patch test for antibiotics. “This is not unexpected, as we know that aminoglycosides cross react,” said Dr. Spring. Eight patients had co-reactions of antibiotics and anesthetics; five patients had co-reactions to steroids only.

Dr. Spring reported that she has no relevant disclosures.