CD17 When the allergen is in the antidote: sodium metabisulfite contact allergy in an adrenaline autoinjector

Abstract

A 9-year-old girl with atopic eczema, asthma, chronic spontaneous urticaria and multiple non-IgE-mediated food allergies was referred for assessment of suspected allergic contact dermatitis to medical adhesives and fragranced products. Patch testing after 96 h revealed a positive reaction to sodium metabisulfite alone. Review of her exposures identified that her prescribed adrenaline autoinjector – administered on a single previous occasion – contained sodium metabisulfite. Sodium metabisulfite is included in the British Society for Cutaneous Allergy (BSCA) standard series at a concentration of 1.0% in petrolatum. At our centre, between 2002 and 2025, 8798 patients underwent patch testing with the BSCA standard series, of whom 335 demonstrated a positive reaction to sodium metabisulfite. Our case represents the only identified case in which sodium metabisulfite contact allergy has occurred in a patient prescribed an adrenaline autoinjector. Sodium metabisulfite is a nonactive excipient added to adrenaline autoinjectors as an antioxidant to prevent oxidative degradation and loss of potency, thereby ensuring drug stability and effectiveness during emergency use. At present, all licensed adrenaline autoinjectors in the UK, including EpiPen®, Jext® and Emerade®, contain sodium metabisulfite as an excipient, and sulfite-free alternatives are not available. Patch testing with sodium metabisulfite remains the most reliable method for identifying sulfite contact allergy and may also assist in the evaluation of patients reporting immediate reactions to sulfite-containing products. Although sulfite sensitivity has been associated with respiratory symptoms, clinical guidelines consistently emphasize that adrenaline must not be withheld in sulfite-allergic patients during life-threatening emergencies. The risk of untreated anaphylaxis far outweighs the risk associated with preservative exposure. This case highlights the counselling conundrum arising from avoidance advice when the allergen is an integral part of the antidote in cases where excipients are embedded within essential emergency and lifesaving medications.