AN ASSESSMENT OF THE PHOTOTOXIC HAZARD OF A PERSONAL PRODUCT INGREDIENT USING IN VITRO ASSAYS.

Where substances are intended for use in personal products applied to the skin an assessment of potential phototoxic hazard is required. This report describes a tiered testing strategy involving in vitro assays used for the phototoxic hazard assessment of a personal product ingredient (Ingredient X). The initial assay was measurement of a UV/visible absorption spectrum to identify absorption at rele-vant wavelengths. This was followed by in vitro assays for phototoxicity (3T3 cell neutral red uptake phototoxicity test) and photoallergy (photobinding to human serum albumin). These in vitro screens gave equivocal results for Ingredient X which appeared to suggest a weak phototoxic reaction. To further evaluate the phototoxic hazard of Ingredient X to human skin, a phototoxicity assay using a 3-D human skin model was conducted. Ingredient X did not cause phototoxicity in this assay. Overall conclusions from these studies were that although Ingredient X showed slight intrinsic potential for photoactivation, it was unlikely to present a hazard to human skin. This report illustrates the value in a step-wise strategy of the use of human skin models to help interpret the results of other in vitro phototoxic-ity assays.

3-D skin model, 3T3 NR PT, 3T3 cell assay, Chloropromazine (CPZ), DMEM, EBSS, Human serum albumen (HAS), In vitro 3T3 cell neutral red uptake phototoxicity test, MTT, MTT ET-50 tissue viability assay, MTT assay, Mean photo effect (MPE), Monomer HSA (mHSA), Neutral red (NR), Neutral red uptake (NRU), Newborn bovine serum (NBS), Phosphate buffered saline (PBS), Photoirritation factor (PIF), Phototoxic, SkinEthic, Thiazolyl blue, UV light, UVB filter