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.