pH
Also called: Potential of hydrogen, Skin pH
pH measures how acidic or alkaline something is. In skincare, it matters because the skin surface is naturally mildly acidic and barrier enzymes work best in that environment.
At a glance
- Healthy stratum corneum is mildly acidic, often around pH 4.1-5.8.
- Skin pH affects barrier function, enzymes, microbiome balance, and irritation.
- Low pH is not automatically better; formula and tolerance still matter.
On this page
The short answer
pH is a scale for acidity and alkalinity. Skin is not neutral; the stratum corneum is naturally mildly acidic.
A 2018 review describes physiological stratum corneum pH as about 4.1-5.8 and explains that pH influences barrier function, lipid processing, epidermal differentiation, desquamation, and microbial balance[1].
Why skincare people talk about pH
The outer skin barrier uses enzymes that behave differently at different pH levels. A review on stratum corneum acidification explains that acidic pH helps processes involved in ceramide generation and permeability barrier function[2].
That is why very harsh, alkaline cleansing can leave some skin feeling tight, dry, or easily annoyed.
Mads's practical read
Do not chase pH numbers for every product. For cleansers and exfoliating acids, pH can matter. For a moisturizer, the bigger question is often simpler: does it calm your skin, support the barrier, and feel good enough to use every day?
Keep reading
Common questions
Is low-pH skincare always better?
No. Skin likes a mildly acidic environment, but very acidic formulas can irritate. The right pH depends on the product type and your skin.
Does cleanser pH matter?
It can. Harsh alkaline cleansing can disturb the skin barrier for some people, especially if the skin is already dry, sensitive, or irritated.
Citations
- pH in nature, humans and skin - Journal of Dermatology, 2018
- Stratum corneum acidification: how and why? - Experimental Dermatology, 2015