Which components in broad-spectrum sunscreens are most necessary for adequate UVA protection?

Abstract

There is an increasing need for broad-spectrum sunscreens that afford adequate UVA protection. In the selection of such a sunscreen, the sun protection factor is of no real value because it gives an indication of only the UVB protection. As long as the methods used to determine the real UVA protection factor are not standardized, the most valid information is the formula of the sunscreen. To determine the components that are most necessary for optimal UVA protection, different components were compared separately and in combination in human subjects by different methods. The physical agents tested gave only relatively weak UVA protection in both the shorter and the longer UVA ranges. Dibenzoylmethane derivatives are more efficient than the physical agents, but only in the shorter UVA range. The UVA protection afforded by the combination of a dibenzoylmethane derivative and physical agents appears to be cumulative.