[Photoprotection, cancer protection and solar protection factor].

Sun protection factor of sunscreens is assessed by their ability to inhibit UV-induced erythema. A correlation between sun sensitivity and density of DNA damage has been established. However the ability of suberythematous irradiation to induce DNA damage suggests that this correlation is not linear. Therefore, exposure to sunrays, extended because of a delayed erythema, can lead to more DNA damage than it is usually believed. The danger of long term of sunscreens use is therefore real, more especially as they may offer different protection factors for different biological end-points.