A novel ex vivo technique to assess the sand/rub resistance of sunscreen products.

A novel ex vivo technique has been used to assess the sand/rub resistance of topical sunscreens. The technique is based on transmission spectrometry using excised human epidermis as the substrate. The sun protection factors (SPFs) of 10 sunscreen products were measured prior to, and after agitation with sand. It was found that the different products retained varying amounts of their photoprotection after agitation, ranging from 40 to 85%. This technique provides a less expensive, less time-consuming and less experimentally problematic alternative to in vivo testing.