Background: Immediate IgE-mediated hypersensitivity reactions to polyethylene glycol (PEG) are rare. Our understanding of PEG hypersensitivity reactions is limited. We evaluate the clinical characteristics and investigation outcomes of the largest cohort of PEG allergic patients reported so far. Method: 44 patients investigated for suspected PEG allergy across four UK tertiary allergy centres between October 2013 and December 2020 were studied. Clinical characteristics, details of 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. Seven PEG-allergic patients reported tolerance to H1 antihistamines containing PEG. Administration of mRNA COVID-19 (n=5) or AZ COVID-19 vaccines (n=14) was tolerated in 16 patients. 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. We observed no correlation in PEG dose and concentration between the implicated and tolerated PEG-containing drugs. Further studies are required to understand PEG thresholds and PEG equivalent doses of various administration routes. COVID-19 vaccines were tolerated by all exposed.

Background: Although well described in adults, there are scarce and heterogeneous data on the diagnosis and management of chronic urticaria (CU) in children (0-18 years) throughout Europe. Our aim was to explore country differences and identify the extent to which the EAACI/GA²LEN/EDF/WAO guideline recommendations for paediatric urticaria are implemented. Methods: The EAACI Taskforce for paediatric CU disseminated an online clinical survey among EAACI paediatric section members. Members were asked to answer 35 multiple choice questions on current practices in their respective centres. Results: The survey was sent to 2,773 physicians of whom 358 (13.8%) responded, mainly paediatric allergists (80%) and paediatricians (49.7%), working in 69 countries. For diagnosis, Southern European countries used significantly more routine tests (e.g., autoimmune testing, allergological tests, and parasitic investigation) than Northern European countries. Most respondents (60.3%) used a 2nd generation antihistamine as first- line treatment of whom 64.8% up dosed as a second- line. Omalizumab, was used as a second line treatment by 1.7% and third-line by 20.7% of respondents. Most clinicians (65%) follow EAACI/WAO/GA2LEN/EDF guidelines when diagnosing CU, and only 7.3% follow no specific guidelines. Some clinicians prefer to follow national guidelines (18.4%, mainly Northern European) or the AAAAI practice parameter (1.7%). Conclusions: Even though most members of the Paediatric Section of EAACI are familiar with the EAACI/WAO/GA2LEN/EDF guidelines, a significant number do not follow them. Also, the large variation in diagnosis and treatment strengthens the need to re-evaluate, update and standardize guidelines on the diagnosis and management of CU in children.