Which sun protection should I choose? With which SPF? In a sun cream or moisturiser with SPF? Why so many “anti-sun” prevention messages? What is the impact on vitamin D? Many questions arise when the topic of sun protection is addressed. The first edition of Cosmetic Days, organised by Cosmed and held in Marseille on 6 and 7 December, was an opportunity to provide answers to many of them.
1. Why should I protect myself from the sun?
Solar radiation is actually composed of several types of radiation, distinguished by their radiation, distinguished by their wavelength:
• From 200 to 400 nm: ultraviolet (UV) radiation
• From 400 to 800 nm: visible radiation
• From 800 to 1400 nm: infrared radiation (IR)
The shorter the wavelength, the more energetic the radiation, and therefore the more aggressive. It is thus UV rays that are most likely to cause damage to the skin, again depending on the wavelength:
• 200 to 280 nm: UVC is potentially the most harmful, but it is blocked by the ozone layer and does not reach us
• From 280 to 320 nm: UVBs cross the skin barrier and the stratum corneum (the most superficial layer of the skin) and reach the epidermis
• From 320 to 400 nm: UVA rays penetrate deeper, to the dermis
What are the effects on the skin?
• At the level of the stratum corneum, UVB and UVA dry the skin.
• In the epidermis, UVA triggers the mechanisms that allow tanning to occur; UVB can cause sunburn; the combined action of UVB and UVA causes skin cancers: basal and …
