Self-reported penicillin allergy common in chronic urticaria

By Bianca Nogrady 
Patients with chronic urticaria have a significantly higher incidence of self­-reported penicillin allergy than the general population, a study has found. 

The retrospective study, using the medical records of 11,143 patients at a US specialist allergy and immunology clinic, showed that 33% of the 1332 patients with chronic urticaria self-reported penicillin allergy. This equated to a prevalence of self-­reported penicillin allergy among patients with chronic urticaria that was threefold higher than that in the general population, according to the study findings published in the Annals of Allergy, Asthma and Immunology. 

Only five patients who had both chronic urticaria and self ­reported penicillin allergy had undergone penicillin skin testing, and four of those five tests – as well as the subsequent oral amoxycillin challenge – were negative. 

A total of 1516 patients self­-reported penicillin allergy, 29% of whom had a diagnosis of urticaria and 14.5% had chronic urticaria on medical review. 

The authors said it was important to study self-­reported penicillin allergy because even though fewer than 10% of those patients were genuinely allergic to penicillin, their self­-reported allergy meant they were often treated differently. 

Commenting on the study, Professor Constance Katelaris said patients with chronic urticaria, who may experience an exacerbation two or three times a week, will often blame it on what they were exposed to immediately prior to the exacerbation. 

‘If the history of penicillin allergy is decades old, then it’s worthy of being investigated with referral to a specialist clinic for skin tests followed by a challenge,’ Professor Katelaris, senior staff specialist at Campbelltown Hospital and the University of Western Sydney, told Medicine Today. 

Penicillin allergy is vastly over self­ reported, she noted. 

‘This is a costly misdiagnosis for the community and the healthcare system because these people end up on more complicated intravenous drugs, they need hospitalisation and they often end up using second­ or third­line drugs.’
Ann Allergy Asthma Immunol 2016; http://dx.doi.org/10.1016/j.anai.2015.11.020. 

Picture credit: © Dr P. Marazzi/SPL.