Sunscreen has an image problem. It is filed mentally under beaches and holidays, which means it gets used on the days it matters least and skipped on the several hundred days it quietly matters most.
Cloud and glass
The wavelengths associated with long-term changes in skin — loss of firmness, uneven tone, marks that linger — pass through cloud, and pass through ordinary window glass. A grey Tuesday at a desk beside a window is not a day off.
This is also why sunscreen is the most useful step for anyone working on discolouration. Fading a mark while continuing to expose it is a slow argument with yourself.
The amount
Most people apply considerably less than the amount sunscreens are tested at, which lowers the protection well below the number on the bottle. A practical fix: apply more than feels elegant, in two thin passes rather than one, and do not forget the sides of the neck, the ears, and the strip in front of the hairline.
Reapplication, realistically
Reapplying every couple of hours is right for a day outdoors. It is not realistic — or particularly necessary — for a day spent mostly indoors away from windows. Perfect reapplication is not the entry fee. Wearing it at all in the morning is most of the benefit.
Mineral or chemical
Mineral filters, chiefly zinc oxide, sit on the surface. Other filters absorb and dissipate energy instead. Neither category is inherently better for skin, and the choice is mostly about tolerance and how a formula feels and looks on you.
If you have reacted to a sunscreen before, a mineral formula is a reasonable next thing to try — but the reaction may equally have been to fragrance or another ingredient rather than the filter itself.
The honest summary
The best sunscreen is the one whose texture you do not resent at eight in the morning. Finish the bottle, buy it again, and put it on the days that feel unremarkable.
