[Actinic erythema, false innocuousness of UV.A].

The number of skin cancers is doubled every ten years. The responsibility of excessive sun exposure is incontestable as much for what concerns spino and baso cellular epitheliomas as for malignant melanomas. Over-exposure to ultraviolet B rays was considered as the determining cause of skin cancer and the entire prevention campaign was limited to the safeguard from these rays only. In reality, ultraviolet B rays are not uniquely responsible. Recent studies show that ultraviolet A rays, previously considered innocuous, are on the contrary aggressive as well and in a very deceiving way: it appears that it is the exposure to these rays in weak but repeated doses which are the most dangerous. It appeared that the visually determined value of MED was unchanged but the minimal dose responsible for color changes detectable with chromameter was decreased in the presence of UV.A for 3 subjects out of 4. This decrease was about 50% of the value obtained with UV.B alone. The strategy of protection needs to be completely reconsidered, particularly because today's lifestyle favors the exposition to ultraviolet A rays. There is an increase in exposure to UV.A rays when protection is limited only against ultraviolet B rays, giving a false sense of security especially to those who frequent tanning salons. It is therefore necessary to limit exposure time, use sunscreens protecting against not only UV.B, but also UV.A rays, and prohibit tanning salons. Public educational measures are inexistant, but should be introduced hastily in all public services.