Good evidence
Cholesterol
INCI: Cholesterol · also the third barrier lipid
The same molecule with the bad dietary reputation, doing an entirely different job. In the stratum corneum it is about a quarter of the lipid mortar, and it is the one whose production falls off most steeply with age.
Why it is here
The molecule with the bad reputation, doing its best work on your face. Older skin makes less of it, so in a cream for people with birthdays it gets to lead.
Cholesterol gives the lipid lamellae their fluidity. Without it the sheets pack too rigidly and the barrier stops behaving like a living membrane. Aged skin makes measurably less of it, which is why cholesterol-dominant lipid mixtures do something in older skin that equimolar mixtures do not. This is one of the few places in skincare where the optimal formula genuinely changes with age.
The receipt
A 3:1:1:1 mixture with cholesterol as the dominant lipid significantly accelerated barrier recovery in chronologically aged human skin at 6 hours after tape stripping, while a free fatty acid dominant mixture significantly delayed recovery in aged mice at 3, 6 and 24 hours.
Optimal ratios of topical stratum corneum lipids improve barrier recovery in chronologically aged skin. Journal of the American Academy of Dermatology, 1997. in vivo animal and human, n = aged hairless mice over 18 months and chronologically aged human skin at 80 plus or minus 5 years, n equals 6 for the human arm. PMID 9308554
In practice
- Typical use
- 0.1 to 1 percent, sized against the ceramide and fatty acid content rather than chosen on its own. In older skin the published argument is for cholesterol to be the dominant lipid of the three.
- Keep apart from
- Nothing. The only mistake documented in this literature is getting the ratio wrong, not combining cholesterol with something else.
- Cautions
- None notable. Topical cholesterol does not affect blood cholesterol. It is a structural lipid here, applied at fractions of a percent.
Questions people ask
Is putting cholesterol on my skin bad for me?
No, and the confusion is purely nominal. Dietary and serum cholesterol are a cardiovascular conversation. Stratum corneum cholesterol is a structural lipid your skin manufactures on purpose, making up roughly a quarter of the barrier mortar. Applying it topically at a fraction of a percent has no bearing on your blood lipids.
Why does cholesterol matter more as you get older?
Because epidermal cholesterol synthesis declines with age more than the other two lipids do, and barrier recovery slows with it. In the 1997 study, a cholesterol-dominant mixture accelerated recovery in aged human skin at six hours where an equimolar mixture only trended. It is one of the few age-specific findings in the barrier literature.
Can I just use more fatty acids instead?
The data says no, quite pointedly. In the same 1997 work, a free fatty acid dominant mixture significantly delayed barrier recovery in aged skin at three, six and twenty-four hours. More lipid is not better lipid. Which of the three dominates is the variable that decides whether the mixture helps or hinders.