Polyethylene glycol hypersensitivity, patient outcomes in a seven year retrospective study.

BACKGROUND: Immediate IgE-mediated hypersensitivity reactions to polyethylene glycol (PEG) are rare. Our understanding of PEG hypersensitivity is limited.

OBJECTIVE: We evaluated the clinical characteristics and investigation outcomes of the largest cohort of PEG-allergic patients reported.

METHODS: 44 patients investigated for suspected PEG allergy across four UK tertiary allergy centres between October 2013 and December 2020 were studied. Clinical characteristics, index reaction, and approaches to and outcomes of allergy investigations were analysed.

RESULTS: PEG hypersensitivity was confirmed in 42 of 44 cases. Macrogol laxatives were the most common index drugs reported (23%), followed by depo-medroxyprogesterone (19%), oral penicillin V (10%), and depo-methylprednisolone (10%). 61% experienced grade III anaphylaxis. Intradermal testing (IDT) increased the diagnostic sensitivity from 51% to 85%. Five patients experienced systemic reactions during IDT. Of the five patients, two were skin prick test (SPT)-positive to a high molecular weight (MW) PEG. Three patients with negative skin test results had positive drug provocation tests. Seven PEG-allergic patients reported tolerance to H1-antihistamines containing PEG. Administration of mRNA COVID-19 or AZ COVID-19 vaccines was tolerated in all 16 patients to whom they were administered.

CONCLUSION: PEG hypersensitivity is an uncommon cause of drug-induced anaphylaxis. Four index drugs accounted for two-thirds of cases and reactions to these drugs should prompt PEG hypersensitivity investigations. PEG IDT increases diagnostic yield. The role of SPT with higher MW PEGs requires further attention. Further studies are required to understand PEG thresholds and PEG equivalent doses of various administration routes. COVID-19 vaccines were tolerated by all exposed.