Consumers, cosmetics and skin sensitizers

Abstract: Background Chemical products, cosmetics and other products handled by consumers and workers frequently contain contact allergens (skin sensitizers). Contact allergens are low-molecular substances which may induce contact allergy (Type IV allergy) after contact with skin. 15-20% of adults are allergic to one or more of the most common contact allergens, which can cause allergic contact dermatitis (eczema) on any part of the body, although the hands and face are the most common sites. Contact allergy is a lifelong condition, requiring avoidance of further skin exposure to the allergen, in order to minimize the risk of developing contact dermatitis. Aim The main aim of this thesis project was to contribute to a scientific basis for preventive measures to reduce contact allergy and dermatitis. Skin sensitizing hair dye substances and preservatives in products frequently used by consumers were of special concern. Methods In study I and II, we assessed the occurrence and use pattern of skin sensitizing hair dye substances in hair dye products available to consumers in one Northern European country and one Southern European country, based on ingredient labeling. In study III, we examined if typographical design and the order of the list of ingredients could improve the readability of product ingredient labels. This was done by comparing the readability of original product labels versus alternative formats we developed, using several quantitative and qualitative measures. Study IV was an experimental clinical study, repeated open application test (ROAT), in which we examined whether permissible concentrations of the preservative methylisothiazolinone (MI) in cosmetic rinse-off products had the potential to elicit allergic contact dermatitis. Main findings In study I and II we showed that many different potent skin sensitizing hair dye substances are commonly used in oxidative hair dye products on the market and the products contain a “cocktail” of these sensitizers. In study III we showed that rather simple adjustments in the design of cosmetic product ingredient labels would improve their readability and understanding significantly. In study IV we showed that cosmetic rinse-off products preserved with 100 ppm or 50 ppm MI elicited allergic reactions in the majority of previously sensitized individuals.