[External photoprotection]

Sunscreens go beyond the field of cosmetology to enter that of preventive or curative medicine. The anti-sun product is a preparation in which "filters" selective for UVB and/or UVA are associated with mineral powders called "screens" that are either dissolved or dispersed in an excipient. Modern products also contain compounds protecting against free radicals, anti-inflammatory agents, biosynthetic melanin or topical psoralens. Sunscreen efficacy tests provide "protection factors" against UVA and/or UVB, and/or infrared radiations. Testing the resistance of these indices to time and to immersion or sudation is necessary to evaluate the substantiality and remanence of sunscreens. These parameters enable sunscreens to be classified into four families with increasing activities: weak, fair, high and major protection. Protecting healthy subjects against solar radiation requires "common sense" and the choice of a sunscreen based on its dermatological risk depending on the phototype, the circumstances of exposure to sun, the regions exposed and the chemical formula of the compound.