Open Access CASE REPORT AMERICAN JOURNAL OF MEDICAL AND CLINICAL SCIENCES, 2022 VOL 7, NO. 1, PAGE 1 – 2 Anaphylaxis to the Pfzer/BioNTech COVID-19 Vaccine with Positve Polyethylene Glycol Skin-Prick Test in Brazil Luiz Werber-Bandeira 1 *, Bruno Braga 1,2 , Thiago Bandeira 1,2 , Elisa Almeida 1,2 , Isabela Bandeira 1,2 and Aderbal Sabra 2 1 Clinical and Experimental Immunology and Allergy Service, Santa Casa da Misericordia do Rio de Janeiro/IMUNODERM clinic/Universidade Estácio de Sá (UNESA), Rio de Janeiro, Brazil. 2 Food Allergy and Autism Unit of the Clinical Immunology Service, Santa Casa da Misericordia do Rio de Janeiro, Rio de Janeiro, Brazil. Contact Luiz Werber-Bandeira  Clinical and Experimental Immunology and Allergy Service, Santa Casa da Misericordia do Rio de Janeiro/ IMUNODERM clinic/Universidade Estácio de Sá (UNESA), Rio de Janeiro, Brazil. © 2022 The Authors. This is an open access artcle under the terms of the Creatve Commons Atributon NonCommercial ShareAlike 4.0 (htps:// creatvecommons.org/licenses/by-nc-sa/4.0/). ABSTRACT A 56-year-old male patent atended at the Medicine Allergy Secton with a current history of itchy red spots on the body reported that a few hours afer receiving the the Pfzer/ BioNTech messenger RNA (mRNA) COVID-19 vaccine, started with red and pruritc lesions. On physical examinaton, the patent did not show any considerable alteraton. Under dermatological examinaton difuse red urtcarial lesions were present in the thoracic region. A biopsy of the urtcarial lesion for histological analysis and epicutaneous-prick test (SPT) with polyethylene glycol (PEG) 335, 600, 3350 and 6000 with reading afer 15 minutes were performed. Urtcaria biopsy showed eosinophilic and lymphocytc infltrate and SPT was positve for PEG 6000 (wheal size 5mm). The patent was treated with an anthistamine and cortcosteroid 30mg per day for 5 days. Upon returning, the lesions had disappeared. PEG allergy is not so common and it seems to occur to higher molecular weight PEGs or higher concentratons. However, since the use of this molecule as an excipient in mRNA vaccines have no precedent before COVID-19, not much informaton was available and anaphylaxis reactons to mRNA vaccine from Pfzer/BioNTech COVID-19 induced or supposedly induced by PEG have been reported. ARTICLE HISTORY Received 01 April 2022 Accepted 28 April 2022 Published 03 May 2022 KEYWORDS Anaphylaxis; COVID-19; mRNA vac- cine; polyethylene glycol. Introducton Cases of anaphylaxis afer vaccinaton with the Pfzer/BioNTech mRNA vaccine against COVID-19 have been reported since the beginning of its use [1] and, as the cause of this allergy has not yet been fully clarifed, the excipients used were considered as potental allergens causing those reactons. Although excipients are inert ingredients, most of the tme without pharmacological actvity, the PEG molecule, as it was one of the excipients used initally in mRNA vaccines, was considered as a candidate allergen [2] and even confrmed as the cause of these reactons in some cases [3]. We report here the case of a patent who developed anaphylaxis afer receiving the mRNA vaccine from Pfzer/BioNTech, in which a reacton to PEG 6000 was detected in the epicutaneous-prick test. Case Report A 56-year-old male patent atended at the Service of Clinical and Experimental Immunology and Allergy - Santa Casa da Misericórdia do Rio de Janeiro-Brazil-General Hospital with a current history of itchy red spots spread over the body reported that a few hours afer receiving the Pfzer/BioNTech mRNA vaccine against COVID-19, started with red and pruritc lesions. Although being a long-term hypertensive patent under use of amlodipine and losartan he did not have any reports of drug allergies in his medical history. On physical examinaton, the patent was without fever, with stained mucous membranes, acyanotc, and anicteric, with head and neck unchanged. Nasal mucosa was normal, as well as the oral cavity. Heart rate was normal with 70 beats per minute, and blood pressure of 120x80 mmHg, abdomen with painless faccidity, bilateral and symmetrical pulses. Upon dermatological examinaton difuse red urtcarial lesions that disappeared with the pressure of a glass slide were present in the forearms, thorax and back (Figure 1). Biopsy of a lesion with punch 4 for histological analysis and epicutaneous-prick test with PEG 335, 600, 3350 and 6000 with reading afer 15 minutes were performed. As a result the following readings were obtained for PEG 335: (1mm, negatve), PEG 600: (1mm, negatve), PEG 3350 (3mm), considered negatve and PEG 6000: (wheal size 5mm) positve. The negatve control: phenolic saline soluton was (negatve) and the positve control: histamine 1mg/mL was positve, (9mm) (Figure 2). Histopathological examinaton of the skin biopsy showed retcular dermis with separaton of collagen bundles and scant perivascular and intersttal infammatory infltraton consistng of lymphocytes, neutrophils and eosinophils characterizing urtcaria.