Step into the sun and it’s not just your eyes that sense the light. Your skin contains photoreceptors like those in the retina, allowing it to mount an immediate defence against damaging ultraviolet radiation.
The skin tans by producing melanin, a pigment that protects DNA from dangerous UV rays. We already know that one component of the UV rays – called UVB – ramps up melanin production a few days after sun exposure in response to DNA damage in the skin. But another component of the radiation – UVA – encourages pigment production within minutes.