when to apply, what to keep apart in time, what the season changes
Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.
Three sizes in one archive — from a sheet on the fridge to a poster on the wall.
This is not medical advice. The sheet carries established practice and manufacturers’ instructions, not treatment. For any skin condition, and before any course, see a doctor.
The US regulator requires a sunburn alert on products containing AHAs. The basis is testing in which four weeks of use roughly doubled the skin’s sensitivity to ultraviolet light.
The important part of that alert is its second half: use a sunscreen "and for a week afterwards". That is how long the raised sensitivity persisted before returning to normal.
A week skipped after a course of acids therefore costs exactly what a week skipped during it costs — and almost nobody mentions that second half.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 6 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.
