Formulation of Sunscreens for Optimal Efficacy.

Skin exposure to solar radiation can cause many adverse effects. In addition to the sun protection factor (SPF), a parameter associated with Ultraviolet B (UVB) protection, significant evidence emphasized the crucial importance of a well-balanced protection against ultraviolet A (UVA) and for some indications, against high-energy visible light. Synergy between UV filters and filter photostability together with film-forming ingredients such as polymers that ensure the homogeneous distribution of UV filters on the skin are key factors to avoid UVA- and UVB-provoked detrimental effects of solar radiation. Clinical studies mimicking real conditions of use have been performed. The results show that a well-balanced sunscreen with at least an SPF-to-UVA protection factor ratio < 3 provides the most effective protection against DNA damage, skin photoimmunosuppression, photodermatoses, and pigmentation disorders. In addition, cosmetically pleasant sunscreens allow a sufficient amount to be applied and re-applied by consumers, ensuring continuous and even coverage of the exposed skin.