The influence of sunscreen type on photoprotection.

Twenty-five volunteers took part in this study whose aims were to determine whether there was any difference between the applied amounts of a chemical and physical sunscreen of the same sun protection factor (SPF); whether the SPF of a chemical sunscreen influenced the quantity applied; and whether individuals who burnt easily in sunlight tended to apply more sunscreen than those who tolerated sun exposure. We found that most subjects choose to apply about two-thirds the quantity of physical compared with chemical sunscreen. This reduction in amount applied is likely to lead, in practice, to the physical sunscreen providing a SPF of about one-half of that achieved with the chemical sunscreen. In sunscreens in which the only variation was the concentration of the active organic chemical absorbers (and hence SPF), there was no difference in the amount of sunscreen applied and so the protection afforded can be assumed to increase in line with the SPF. While there was no statistically significant difference between the amounts applied by subjects of different skin types, there was a tendency for subjects with the lower skin types to apply more sunscreen than those who burnt less easily.