Every skincare article ends by telling you to wear sunscreen, which makes it easy to skim past. The part worth reading once is why it has to be daily rather than sunny-day.
UVA does not care about the weather
Sunlight reaches skin as two kinds of ultraviolet. One is strongest in summer, at midday, outdoors, and it is the one that burns. The other is roughly constant through daylight hours, passes through cloud, and passes through window glass — and it is the one most associated with how skin looks after decades of it.
That is what broad-spectrum means on a label: both kinds, not only the one you can feel. It is also why a grey January morning at a desk by a window still counts.
How much, which is where it usually goes wrong
Sunscreens are tested at a thickness almost nobody applies. A useful measure for face and neck is about half a teaspoon, or two long strips squeezed along two fingers — noticeably more than feels necessary.
An SPF 50 applied thinly is not an SPF 50.
Reapplying every couple of hours matters if you are outdoors, swimming or sweating. Indoors most of the day, the morning application is doing the bulk of the work.
What it will not do
Sunscreen does not make sun exposure harmless, and doubling the number on the bottle does not double anything. It is a habit rather than a shield, and its value is in how many mornings it happens.
No night cream substitutes for it, ours included — and a cream with retinol in it makes the morning habit matter more, not less. If you keep one thing from anything in this Journal, keep this one.
This article is general information, not medical advice. Speak with a qualified healthcare professional about your own skin, and do not use retinol during pregnancy or nursing without their guidance.
