You can only tell if a product is working by comparing one change against a record you can repeat. One glance in the mirror is not that record. The American Academy of Dermatology warns that switching to a new acne product every few days can worsen acne (AAD).
In Oleah, the morning face scan is the record. Look at the day 3 check-in, the day 7 report and the day 14 report, instead of one mirror glance.
How long does skin turnover take?
There is no single number. Two different figures often get quoted as if they were the same thing.
- Stratum corneum transit is the time for the outer horny layer of skin to renew. Grove and Kligman measured it in 1983 and found it was approximately 20 days in young adults, and more than 10 days longer in older adults. (PubMed 6827031)
- Full epidermal turnover is a different measure. Maranke Koster writes that human epidermis is estimated to turn over every 40 to 56 days. (Koster, Making an epidermis, PMC2861991)
Other studies give other figures for their own methods: Weinstein and colleagues reported a mean epidermal turnover time of 39 days (PubMed 6725985), and Bergstresser and Taylor derived 45 days for forearm skin (PubMed 871385). DermNet says keratinocytes are normally renewed every 15 to 30 days. (DermNet, structure of the epidermis)
None of these is a rule for when a serum should show a result.
How long should you give a product?
It depends on the product and what you are using it for. Here is what dermatology sources say for a few common cases.
| Product | What the source says |
|---|---|
| Acne treatment | AAD: some improvement in 4 to 6 weeks, clearing in two to three months or longer. |
| Prescribed acne retinoid | DermNet: 12 weeks or longer before improvement is seen. |
| Niacinamide (nicotinamide) | DermNet cites studies of 4 to 6 weeks (2 percent, facial oil), 8 weeks (4 percent, eyelid wrinkles) and 12 weeks (5 percent, fine lines, pigmentation, texture and red blotchiness). (DermNet) |
For acne treatments, the American Academy of Dermatology, using tips from dermatologist Julie Harper, MD, says that if one works for you, you should notice some improvement in 4 to 6 weeks, and clearing can take two to three months or longer. The same page warns that switching to a new acne product every few days can worsen acne. (AAD)
For prescribed acne retinoids such as adapalene and tretinoin, DermNet says "it may take 12 weeks or longer before improvement is seen." (DermNet, topical retinoids)
The niacinamide study lengths come from DermNet's nicotinamide page. They are the lengths of those studies, not a deadline for every serum. (DermNet, nicotinamide)
How do you set up a fair test?
- Take a photo before you start the new product, in conditions you can repeat: same place, same time of day, same distance.
- Write down the change you are looking for in words a later photo can confirm, such as "flaking around the mouth." "Better skin" is too vague to check.
- Change one product and keep everything else the same.
- Use the morning face scan in Oleah as your record, and look at the day 3 check-in, the day 7 report and the day 14 report. They are a record of visible changes, not a verdict that a product worked.
What about irritation in the first few weeks?
Irritation can show up early. DermNet lists retinoid dermatitis as redness, peeling and dry skin. (DermNet) If a product stings, burns or makes your skin red, wash it off and stop using it. If a doctor prescribed it, ask them first. If your skin stays sore, see a pharmacist or doctor. If it blisters or swells, see a doctor today. If your lips, tongue or throat swell, or you have trouble breathing, call emergency services now. Oleah is not a doctor and does not give medical advice.
FAQ
Does this product actually work?
You can only tell by changing one product at a time and comparing the same skin over the same mornings. Oleah's morning face scan is the record: look at the day 3 check-in, the day 7 report, and the day 14 report instead of one mirror glance.
How do you know if skincare is working?
Compare one change with a record you can repeat. One mirror glance is not that record. In Oleah, the morning face scan is the record. Look at the day 3 check-in, the day 7 report and the day 14 report.
How long does skin turnover take?
There is no single number. Grove and Kligman found stratum corneum transit took approximately 20 days in young adults (PubMed 6827031). Koster estimates full epidermal turnover at 40 to 56 days (PMC2861991). Those are two different things.
How long should an acne treatment take?
The American Academy of Dermatology says some improvement in 4 to 6 weeks, and clearing in two to three months or longer. Switching products every few days can worsen acne (AAD).
Does Oleah tell you the product worked?
No. The day 3 check-in, the day 7 report and the day 14 report follow visible changes in your own face scans. They are not medical advice, and they are earlier than the 4 to 6 week acne window.
Where Oleah fits
Oleah is an iPhone app for the skincare you already own. You add the products on your shelf or in your routine, and each morning you take a quick face scan. Oleah can flag products on your shelf that may not belong together. There is a check-in on day 3, a report on day 7, and a report on day 14. Oleah is not a doctor and does not give medical advice.
The morning face scan is the record. Look at the day 3 check-in, the day 7 report and the day 14 report, instead of one mirror glance.
Related reading: how many serums is too many?, niacinamide and vitamin C and how to tell your skin type
Download the free iPhone beta. Add the products on your shelf, then take a quick face scan in the morning.
Sources
- Grove GL, Kligman AM. Age-associated changes in human epidermal cell renewal. PubMed 6827031
- Koster MI. Making an epidermis. PMC2861991
- Weinstein GD, McCullough JL, Ross P. Cell proliferation in normal epidermis. PubMed 6725985
- Bergstresser PR, Taylor JR. Epidermal turnover time, a new examination. PubMed 871385
- DermNet, structure of the epidermis
- DermNet, topical retinoids
- DermNet, nicotinamide
- AAD, 9 things to try when acne won't clear
Oleah tracks how your skin looks. It is not a medical device. See a doctor about skin conditions.