State of the art sunscreens for prevention of photodermatoses

Abstract

The prevention of photodermatoses implies that the exposure to ultraviolet (UV) light of photosensitive patients is reduced to levels below the threshold of induction of light reactions. The four principal measures of prevention are the following: “ avoidance of sun exposure around midday; “ UV-protective clothes; “ hats; “ use of sunscreen products. Protection of photosensitive patients by sunscreen products play an important role. This is particularly true for the prevention of photodermatoses, which are elicited by UVA. About 50% of the exposure to UVA occurs in the shade, i.e. in the absence of direct sunlight. The amount of UVA in sunlight is high from sunrise to sunset, whereas the intensity of UVB peaks more sharply at midday. Whereas window and car glass materials offer an effective shield against UVB, they are transparent for UVA. Moreover, due to the presence of subclinical and/or apparent eczema in already affected skin areas, the natural protective capacity of the horny layer may be reduced or lost, which will further increase the light sensitivity of the afflicted skin. Which are the ideal properties of state-of-theart sun protection products? Such compounds should be: (i) well tolerated; (ii) cosmetically pleasant; (iii) non-toxic; (iv) equally effective against UVA and UVB; (v) photostable; (vi) water resistant; (vii) with a high ‘Sun Protection Factor’. These criteria should be briefly commented on (adverse properties listed under (i)–(iii) are exclusion criteria). (i) Good tolerance is of primary importance, since such products are often applied under stress conditions to sensitive skin. Skin tolerance requires careful testing and optimisation, since preparations with high protection factors contain relatively large amounts of UV filter substances (see later). Many promising filter substances are rejected at an early stage of development due to their irritant, photoirritant or photoallergic potential. * Corresponding author. Tel.: +33-1-47567701; fax: +331-47567630.