Skip to content

How long does skincare take to work? Give it four weeks at least

6 min read
Two monitors side by side on a designer's desk
Photo by Tran Mau Tri Tam on Unsplash

The short answer

Give most skincare products at least four weeks of daily use before you judge them, and closer to twelve for acne, dark marks or fine lines. The outer layer of skin renews in roughly three to four weeks in younger adults and more slowly with age, so a change you see in the first week is rarely the product. Test one new product at a time and compare photos taken the same way.

Get Baseline

A new serum goes on, and three days later you are looking in the mirror for a difference. Usually there isn’t one yet, and that is normal. Skin changes slowly, and most of the quick changes people notice are the light, the time of day, or a good night’s sleep.

Why four weeks is the floor

The outer layer of your skin is replaced from below all the time. New cells form in the deeper layer and move up to the surface, where they are shed. A product that works on skin, rather than just sitting on top of it, mostly changes the new cells, so its effect only shows once they reach the surface.

How long that takes depends on age. In a 1983 study in the Journal of Gerontology, Grove and Kligman measured how fast the outer layer turned over on the forearm. It took about 20 days in people under 35 and about 28 days in people over 60. That is where the common “28 days” comes from, and why it is a floor rather than a deadline.

How long different products need

Product When to judge it
Moisturiser, cleanser Days to two weeks: comfort and dryness change fast
Sunscreen It works on day one; judge it on feel and whether you wear it
Exfoliating acids Four to six weeks for texture
Retinoids Six weeks or more for texture, months for fine lines
Acne treatments Around twelve weeks, often worse before better
Dark marks Twelve weeks or more, with daily sunscreen

These are rough windows, not promises. If a product stings, burns or causes a rash, stop it: waiting is for products that are comfortable but not yet doing anything.

Test one change at a time

The most common reason people can’t tell what works is that they change several things at once. A new cleanser, a new serum and a new sunscreen in the same month, then the skin improves, and nobody knows why.

A fair test is simple:

  1. Patch test first. Put a little behind the ear or on the jaw and wait 48 hours.
  2. Change one thing. Keep the rest of the routine exactly as it was.
  3. Give it four weeks of daily use before you judge it.
  4. Record what else happened. A flare before your period, a week of travel, a sunburn or a run of poor sleep can all change skin, and none of them is the product.
  5. Decide. Keep it, or stop it and go back to the routine you had.

Photos you can actually compare

Mirrors are bad judges, because you see your face in a different light every time. Photos are better, but only if they are taken the same way. Position, distance and light all change how skin looks: side light shows every bump, flat light hides them, and warm bulbs make redness look worse.

Take every photo in the same spot, at the same time of day, with the same distance from the camera, and with no filters. Then compare them side by side, not from memory.

How Baseline runs the test

Baseline, our skincare routine tracker for Android, is built around this method. On day 0 you take a guided photo: a face outline lines it up, and the app checks alignment, distance and light before you take it. You rate five things yourself, from 1 to 5: oiliness, breakouts, redness, texture and dryness. It never scores your face.

On day 28, 56 and 84 it asks for a new photo and the same five ratings, and shows them beside day 0. When you add a new product it becomes the change being tested for 28 days, with a countdown, and a 48-hour patch-test timer if you want one. Add a second new product mid-test and it warns you. At the end you decide whether you would buy it again.

Before you start a test, it is worth checking your routine for clashes that cause irritation on their own: see which skincare ingredients you shouldn’t mix.

This is not medical advice. For acne that scars, a rash that spreads or anything that worries you, see a dermatologist. A record of what you used, and photos taken the same way, will make that appointment more useful.

  • Skincare
  • Health

Questions people ask

How long should I use a product before deciding it doesn't work?

At least four weeks of daily use for most products, and around twelve for acne treatments, dark marks or fine lines. A moisturiser can feel better in days, but anything that claims to change the skin itself needs the outer layer to renew first.

Why does skin take about four weeks to change?

The outer layer of skin is constantly replaced from below. In a 1983 study by Grove and Kligman, it turned over in about 20 days in people under 35 and about 28 days in people over 60. A product that changes new cells takes at least one full cycle to show at the surface.

Can I start two new products at once?

You can, but you won't know which one helped, or which one caused a reaction. Introduce one new product, give it four weeks, then add the next. If you change two things and your skin improves, you have learned nothing you can repeat.

How long should a patch test last?

Forty-eight hours is the usual window. Put a small amount behind the ear or on the jaw, leave it, and check at 48 hours for redness, itching or swelling before using it on your face.

Why do my before and after photos look so different?

Usually because of the light, not the skin. A photo by a window at noon and one under a ceiling bulb at night can make the same skin look smoother, redder or more uneven. Take every photo in the same place, at the same distance, in the same light.

Keep reading