The literature that comes with the product seems almost deliberately obscure (the company is French, you see… tricky), but it’s something about training the skin to adapt to the sun on a cellular level. Don’t know if I believe that. But I do know this: I have been using Institut Esthederm suncream for ten years, and I always tan but never burn. We call it ‘magic cream’ in my house. It is one of those products that brings out my inner miser. I always carry a spare suncream with me — something intensely revered and luxurious, such as Sisley — so that I can lend that one out and keep the magic cream for my own selfish self.