A scheme for in vitro screening of substances for photoallergenic potential

Safety tests for photoallergenicity have to date used animal models, but in vitro testing, based on mechanistic knowledge, should now be considered. A photoallergen must absorb the wavelengths of light present in sunlight, and after light absorption the molecule must photobind to protein. In contrast, many photoirritants produce excited state singlet oxygen, which causes damage such as oxidation of certain amino-acid residues. An in vitro testing scheme founded on these considerations for the screening of photoallergens is presented.