New Combination of Ultraviolet Absorbers in an Oily Emollient Increases Sunscreen Efficacy and Photostability

INTRODUCTION: It is now recognized that to adequately protect skin from sun damage, sunscreens require a photostable combination of ultraviolet (UV) filters with a suitable level of UVA protection. The total amount of UV filters should be as low as possible to avoid adverse skin reactions, potential environmental impact, and to ensure acceptable texture for better application and usage. METHODS: A synergistic combination of UV filters was selected to obtain a high sun protection factor (SPF) and UVA protection factor (UVA-PF). An oily vehicle was then added to the formula to improve the solubility and the photostability of the lipophilic UV filters. RESULTS: The combination of filters, i.e., terephthalylidene dicamphor sulfonic acid (TDSA), bis-ethylhexyloxyphenol methoxyphenyl triazin (BEMT), and butyl methoxy dibenzoyl methane (BMDM), obtained an elevated SPF as well as a high UVA-PF. Isopropyl lauroyl sarcosinate (ILS), a derivative of a natural amino acid (sarcosine, also known as N-methylglycine) was introduced in this formulation in order to dissolve the oil-soluble UV absorbers and to photostabilize BMDM. The new sunscreen formulation obtained with this combination is photostable and contains a reduced amount of UV filters compared to other sunscreens with the same level of efficacy. CONCLUSION: This report described the steps resulting in the formulation of a new combination of UV filters in an oily emollient, which presents a high UVA-PF (UVA-PF = 38) and a SPF 50+, is photostable, and offers good protection against UV-induced biological damage.