Patients with a remote history of an allergic reaction to penicillin that was not life-threatening appear to be able to tolerate an oral penicillin test, even if the results of skin tests are positive, according to study results reported by Israeli investigators.

Dr. Arnon Goldberg of Meir Medical Center, Kfar Saba, and Dr. Ronit Confino-Cohen at Tel-Aviv University identified 169 subjects who had a non-life-threatening allergic reaction to penicillin that occurred more than 3 years earlier.

Regardless of their response to penicillin skin testing, the participants underwent an oral allergy test with the usual 1-day dosage of penicillin or amoxicillin, on two separate occasions. A total of 272 oral tests were performed, the investigator report in the Annals of Allergy, Asthma, and Immunology indicate.

Out of 137 oral tests performed in patients who had a previous reaction to a skin test, 9 (6.6 percent) had adverse reactions; the 135 oral tests in those with a previous negative skin test produced 5 (3.7 percent) adverse reactions. The differences in adverse reactions between the two groups were not statistically significant.

Follow-up testing was conducted 2 to 6 years later to evaluate the outcomes of further penicillin testing. Fifty-five patients (40.1 percent) had been treated by their primary physician with a total of 66 courses of oral penicillin or amoxicillin for 7 to 10 days.

Of these patients, 32 (58.2 percent) had at least one positive skin test result and two (3.6 percent) had a positive oral test result.

Overall, 52 patients (94.5 percent) tolerated the treatment well, and 3 patients (5.5 percent) reacted to treatment with a mild rash.

It appears that oral penicillin allergy testing can be a safe “diagnostic procedure in these patients when skin testing is not feasible,” Goldberg said in an interview with Reuters Health.

Nonetheless, Goldberg cautioned that the “study is a preliminary one and should be repeated and extended in order to validate its findings.”

SOURCE: Annals of Allergy, Asthma, and Immunology, January 2008.