UVA and UVB are ultraviolet rays emitted by the sun. They enable the skin to tan but are also very harmful. They differ in intensity and wavelengths:
UVB rays have medium wavelengths and act on the skin’s surface. They are responsible for sunburn and burning.
UVA rays have higher wavelengths and penetrate the skin in depth; they lead to accelerated aging and reduce the skin’s elasticity.
In the long term, UVA and UVB rays may be responsible for a range of skin cancers. It is therefore indispensable to use dual sun protection (against UVA and UVB rays), in particular for children.