Published online: June 3, 2019
Approximately 10% of Americans think they are allergic to penicillin, yet studies have shown that 90-95% of these people will be able to take penicillin-based antibiotics. This is important since the penicillin allergy label has been linked to longer and more expensive hospital stays, increased antibiotic side effects, decreased cure rates, and increased rates of “superbugs,” such as Clostridiodes difficile (C diff) and methicillin-resistant Staphylococcus aureus (MRSA). Although allergists have historically evaluated penicillin allergy with skin testing, recent studies suggest that skin testing may not be necessary in low risk individuals.
Authors Drs. Allison Ramsey and S. Shahzad Mustafa conducted a randomized study comparing penicillin skin testing followed by an oral dose of amoxicillin (PST), to 2 test doses of amoxicillin without preceding skin testing, also called a direct challenge (DC). Both PST and DC were administered under medical supervision in an allergy office. The authors included all patients older than five years of age with a history of reacting to penicillin with skin symptoms only, such as itching, rash, hives, or flushing. Patients with more severe reactions, such as swelling or difficulty breathing, were evaluated with usual skin testing or were told to continue to avoid penicillin. Their study is published in The Journal of Allergy and Clinical Immunology: In Practice.
A total of 80 patients were assigned to the PST group and 79 patients were assigned to the DC group. There were 70/80 negative PST, and the 10 PST positive patients were counseled to continue to avoid penicillin-based antibiotics. The 70 patients with negative PST all tolerated a dose of amoxicillin, confirming no allergy, and thus opening the door for penicillin use in the future. There were 76/79 patients who did not have any symptoms with DC, and were therefore told they too could be treated with penicillin-based antibiotics in the future. The 3 patients who experienced symptoms with DC had mild symptoms that resolved quickly. No patients in either group experienced a delayed reaction in the days following their evaluation. The authors showed that a DC evaluation is slightly faster and potentially less expensive than a PST evaluation.
This study is the first of its kind to compare PST to DC in patients with a history of reacting to penicillin with skin symptoms only. There were no patients who experienced a serious reaction in the study, including the group who did not undergo PST and instead were given test doses of penicillin. There were also more positive evaluations in the PST group as compared to the DC group, suggesting that PST may “overcall” penicillin allergy, and continue to lead to the unnecessary avoidance of this important antibiotic. This additional data regarding the safety of DC without preceding PST in patients at low risk for penicillin allergy may help to expand efforts to remove penicillin allergy labels from patient charts.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.