ABSTRACT
Background: Polyethylene glycol (PEG) is a condensed polymer of ethylene glycol used as excipient in over 1000 commonly medicines, as well as for industrial products or cosmetics (shampoo, toothpaste.) where it can act as thickener, solvent, softener or humectant. In relation to the recently developed COVID-19 vaccines and their excipients some questions have arisen in our consultations. Method(s): A 48-year- old woman came to our clinic with doubts about the administration of COVID-19 vaccine. 8 years ago, after rectal administration of a healing suppository for an anal fissure she immediately presented a dry cough and a generalized urticaria which subsided spontaneously without attend to the emergency department. 5 years ago, with the application of an hemorrhoid cream se presented an immediate reaction consisting of cough, difficulty breathing and generalized urticaria. The symptoms subsided spontaneously after 30-45 minutes. The patient reported previous tolerance to both drugs. She has avoided them ever since. All these medicines have in common PEG as an excipient. We performed several studies to find out if PEG was the culprit. Result(s): *Prick test with Casenlax (which contains 10 grams of PEG 4000): negative. *Oral provocation test with Casenlax: we started with the intake of 2.5 grams of Casenlax and after 5 minutes she started with oropharyngeal pruritus, dry cough, feeling of shortness of breath and desaturation (since 98% to 92-90%). The patient was monitored and administered intramuscular adrenaline (0.3 ml), methylprednisolone 60 mg and dexchlorpheniramine 5 mg. The symptoms were controlled after 15-30 minutes. *COVID-19 AstraZeneca vaccine was administered without incident. Conclusion(s): Given the high incidence of reactions to the excipients accompanying the drugs, this should be taken into account when taking the patient's medical history and in the subsequent pharmacological study.