Immunological Mechanisms in Allergic Contact Dermatitis
The most recent example for newly emerging allergens in consumer products is the preservative methylisothiazolinone (MI). MI is used alone or in combination with methylchloroisothiazolinone (MCI) in many products such as cosmetics and paints. The recent 'epidemic' of ACD caused by MI clearly shows the limitations of the in-vivo and in-vitro assays for the identification of contact allergens, of the final product testing, as well as the importance of considering exposure conditions and concentrations used in consumer products and in patch testing. Interesting approaches to reduce the risk of skin sensitization are the chemical modification of known contact allergens to generate less allergenic molecules. In the case of p-phenylenediamine (PPD), which is a contact allergen contained, for example, in hair dyes, addition of a 2-methoxymethyl side chain reduced its sensitizing potency. A recent study showed that a significantly lower number of PPD-allergic individuals reacted to methyl-PPD as compared with their PPD reactivity. A similar approach resulted in the reduction of the sensitization capacity of epoxy resin monomers. These strategies reveal the importance of the mechanistic understanding of the chemistry and biological effects of contact allergens which aids in the development of in-vitro assays for the identification of contact allergens, novel diagnostic techniques and therapies for contact dermatitis.
New Allergens and 'Hypoallergenic' Chemicals
The most recent example for newly emerging allergens in consumer products is the preservative methylisothiazolinone (MI). MI is used alone or in combination with methylchloroisothiazolinone (MCI) in many products such as cosmetics and paints. The recent 'epidemic' of ACD caused by MI clearly shows the limitations of the in-vivo and in-vitro assays for the identification of contact allergens, of the final product testing, as well as the importance of considering exposure conditions and concentrations used in consumer products and in patch testing. Interesting approaches to reduce the risk of skin sensitization are the chemical modification of known contact allergens to generate less allergenic molecules. In the case of p-phenylenediamine (PPD), which is a contact allergen contained, for example, in hair dyes, addition of a 2-methoxymethyl side chain reduced its sensitizing potency. A recent study showed that a significantly lower number of PPD-allergic individuals reacted to methyl-PPD as compared with their PPD reactivity. A similar approach resulted in the reduction of the sensitization capacity of epoxy resin monomers. These strategies reveal the importance of the mechanistic understanding of the chemistry and biological effects of contact allergens which aids in the development of in-vitro assays for the identification of contact allergens, novel diagnostic techniques and therapies for contact dermatitis.