When I say ‘sun damage’, I don’t mean sunburn or the peeling skin you see when someone has spent too long on the beach. I mean the unseen changes in your skin cells caused by ultraviolet radiation from the sun, otherwise known as UVA and UVB rays. This happens every time you are in the sun—even if it’s cloudy, even if you’re indoors, even if (gasp!) you are wearing sunscreen. It’s often termed photoageing (or, in academic journals, ‘dermatoheliosis’, though it’s unlikely you’ll come across that word).