CD15 What is in the soap? Contact allergen prevalence in UK supermarkets and NHS liquid hand soaps

Abstract

Contact dermatitis is a common inflammatory skin disease and a significant public health burden, particularly among healthcare workers. Repeated handwashing causes exposure to surfactants, preservatives and fragrance components in liquid hand soaps, contributing to irritant and allergic contact dermatitis. Contemporary UK data on the allergenic composition of commonly used liquid hand soaps are limited. This study was designed to identify and compare the prevalence of recognized contact allergens in liquid hand soaps in UK supermarkets and within the NHS, using the British Society for Cutaneous Allergy and Chemotechnique Diagnostics allergen series. Ingredient lists of liquid hand soaps were analysed from the top three UK supermarkets and NHS procurement channels. In total, 119 supermarket products and 26 NHS supply chain products were included, representing the full NHS liquid handwash range available at data collection. Ingredients were systematically reviewed against allergens listed in the BSCA standard, cosmetic and fragrance series and the Chemotechnique British standard, cosmetic and fragrance series. Allergen frequencies were recorded and compared between retail and healthcare products. Supermarket liquid hand soaps demonstrated a higher prevalence of fragrance-related allergens, including parfum, linalool, citronellol and cinnamal. NHS products showed a relatively higher prevalence of preservative allergens, including phenoxyethanol, benzoic acid and methylisothiazolinone. Within NHS liquid hand soaps, fragrance allergens were identified in 33% of products, while methylisothiazolinone was present in 15%. Cocamidopropyl betaine was the most frequently identified allergen, detected in 76% of all products. Multiple products in both settings contained more than one recognized contact allergen, indicating potential cumulative allergen exposure. This study demonstrates differing allergen profiles between retail and healthcare liquid hand soaps and highlights ongoing exposure to contact allergens in frequently used products, including the continued presence of methylisothiazolinone. These findings are relevant for dermatology practice and occupational health and may support improved patient counselling, product selection and future formulation practices.