Modern sunscreens may contain at least two UV filters, one with optimal performance in the UVA region and the other one in the UVB region. However, the presence of different UV filters, which usually leads to synergistic effects Tofacitinib in vitro regarding both the final performance and photostabilization of the sunscreen, can also accelerate their decomposition if a photoreaction occurs between the single components (Osterwalder and Herzog, 2010, Gonzalez et al., 2007, Chatelain and Gabard, 2001 and Lhiaubet-Vallet et al., 2010). Despite the wide range of UVB filters, appropriate UVA filters are rare; among them avobenzone is probably the most important
representative. This active ingredient is present in numerous commercial sunscreen and cosmetic formulations. Avobenzone strongly absorbs UVA, but presents significant degradation under UV exposure reducing its UVA protecting effect (Paris et al., 2009 and Bouillon, 2000). The reactive intermediates of photounstable filter substances come into direct contact with the skin, where
they may behave as photo-oxidants or may also promote phototoxic or photoallergic contact dermatitis. The interaction of photodegradation products with sunscreen excipients or skin components like sebum may lead to the formation of newmolecules with unknown toxicological properties (Cambon et al., 2001, Deleo et al., 1992, Rieger, 1997, Schrader et al., 1994 and Nohynek and Schaefery, 2001). Consequently, SP600125 there is an increasing concern
about the phototoxicity and photoallergy of UV filters. Phototoxicity is defined as a toxic response from a substance applied to the body which is either elicited or increased (apparent at lower dose levels) after subsequent exposure to light, or that is induced by skin irradiation after systemic administration of a substance (OECD, 2004). It is as a non-immunological light-induced skin response (dermatitis) to a photoactive chemical, and the skin response is characterized by erythema and sometimes edema, vesiculation, and pigmentation. Phototoxic reactions are comparable with primary irritation reactions in that they may be elicited after a single exposure, thus no induction period is required (Marzulli and Phospholipase D1 Maibach, 1985). Photoallergic contact dermatitis is thought to arise when UV radiation interacts with a chemical to form a hapten or antigen, which in turn triggers a type IV hypersensitivity reaction (Bryden et al., 2006). As organic UV filters are used in increasing amounts, there is gradual emergence of reports of allergic and photoallergic reactions to UV filters on human skin. Epidemiological studies performed using human photopatch test, showed that avobenzone and many other UV-filters were the causal agents of these allergic and photoallergic reactions (Schauder and Ippen, 1997 and Lodén et al., 2011).