Solid Shampoo Is Mostly Not Preserved, in Contrast to Liquid Shampoos Used in Hairdressing—A Market Survey in Four European Countries

BACKGROUND: Hairdressers are frequently exposed to shampoos, both from neat liquid products and dilutions, often with unprotected hands. Shampoos usually contain preservatives. While the level of preservation is guided by risk assessment based on typical consumer exposure, this will underestimate sensitization risk in hairdressers. Lower exposure or avoidance of preservative-containing hair cosmetic products appears important for primary prevention of work-related allergic contact dermatitis among hairdressers. OBJECTIVES: To assess the preservatives (Annex V of the EU Cosmetics Regulation (EC 1223/2009)) used in solid shampoos, compare these to preservatives present in liquid shampoos for professional use, and determine the presence of ingredients with "antimicrobial" function in solid shampoo. METHODS: A physical store check and survey of online sales platforms was performed in four European countries in late 2024. Along with product descriptors, the full INCI labelling was recorded from package labels (or corresponding summaries online) and collected in a spreadsheet. RESULTS: The sample included 172 solid shampoos from various retail sources and 259 liquid shampoos from one online marketplace for professional users. Among solid shampoos, preservatives were found in 31.4%; if "antimicrobial" additives are additionally considered, this share increased to 41.3%. Benzyl alcohol (n = 29) and sodium benzoate (n = 18) were the most common preservatives, benzyl benzoate the most common "antimicrobial" (n = 8). By contrast, all liquid shampoos contained (multiple) preservatives. CONCLUSIONS: Solid shampoo shows potential to provide a less-allergenic working environment for hairdressers. Practical aspects should next be addressed to contribute to broader use of solid shampoos.