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Background: Formaldehyde is a common cause of contact allergy. Hidden formaldehyde, that is, formaldehyde in products without formaldehyde releasers, has previously been detected in cosmetic products. Objectives: The objective of this study was to investigate the content and causes of hidden formaldehyde in leave-on cosmetic products. Methods: The formaldehyde release from 142 cosmetic products, primarily creams, was analysed using the chromotropic acid (CA) method. The study included 130 products with no formaldehyde releasers on the ingredient list and 12 products with formaldehyde releasers. Products without formaldehyde releasers positive to CA, that is, with formaldehyde ≥2.5 ppm, were additionally analysed using high-performance liquid chromatography (HPLC). Formaldehyde release from selected raw materials and packaging were also investigated. Results: Hidden formaldehyde was found in 23 of the 130 products (18%) without formaldehyde releasers on the ingredient list. The average formaldehyde content was 105 ppm (range: 0.5–507 ppm) in products with hidden formaldehyde and 355 ppm (range: 75–637 ppm) in eight products with formaldehyde releasers, selected for HPLC analysis. Impurities of formaldehyde in dihydroxyacetone may be a cause of hidden formaldehyde in self-tanners. No clear pattern was found for the other products with hidden formaldehyde. Conclusions: Changes in regulation are needed to prevent allergic contact dermatitis from hidden formaldehyde in cosmetic products.
Søgaard et al. (Sun,) studied this question.