Nothing works in a week

A skin cell forms at the base of the epidermis, flattens, dries, migrates upward, and eventually leaves. In a healthy adult the round trip takes somewhere near twenty-eight days. In your twenties it can be faster. Past forty it commonly stretches to forty days or more. Nobody has your exact number and it changes with the season.

That single fact should govern how you judge every product you own, and almost nobody uses it that way. A week of a new routine tells you about the routine. It tells you almost nothing about the skin.

• Days 1–3 — texture and tolerance. Does it sting, does it pill under sunscreen, does it feel tacky at hour two, do you actually enjoy using it. These are real answers and you get them immediately.
• Week 1 — hydration. Surface water content responds fast. Skin can look plumper and less tight within days. This is genuine, it is also the easiest thing in skincare to achieve, and it is not evidence of anything deeper.
• Week 4 — one full turnover. The first point at which changes in the look of texture and smoothness mean something. Also the point where an irritation you have been ignoring stops being a settling-in period and starts being a signal.
• Weeks 8–12 — evenness of tone. Slow. Best judged in a photograph, in the same light, at the same time of day, without makeup.
• Anything faster than those windows is water, light, or wishful thinking.

You never see your face fresh. You see it in a bathroom mirror you have looked into ten thousand times, in light that changes with the weather, after a night that was either long or was not. Human perception is extremely bad at slow change and extremely good at inventing it after spending money.

The plural of "I think it is working" is not evidence. Take the photograph.

So: one photo at the start, bare skin, no filter, window light, phone at the same distance. Then forget about it for four weeks. Compare the two side by side rather than against the picture you have been carrying in your head. It is unglamorous and it is the only method available to you at home that is not self-deception.

The other reason routines fail to teach you anything is that people rebuild them all at once. Four new products on the same Sunday, and when something improves or something stings you have no idea which one did it.

Add one product. Give it four weeks. Then add the next. It is slower in the way that anything that produces information is slower, and at the end of three months you know what actually belongs in your routine instead of owning eleven things and trusting all of them equally.