WOMEN’S HEALTH

pH IN SKINCARE

General practitioner Dr Ginni Mansberg, one of Australia’s leading women’s health experts, explains the role of pH in the skin and how topical products interact with the skin microbiome to change the skin pH.

I rarely hear people discussing the role of pH in the skin, and yet, increasing evidence suggests it is one of the most important factors impacting skin health.

Therefore, staying up to date on the latest research to advise your patients on the appropriate selection of topical products is essential.

WHAT IS PH?

“Potential of Hydrogen”, AKA pH, is simply a measure of how many hydrogen ions something has – in other words, how acidic or alkaline something is.1 Human skin is naturally slightly acidic.2 This acidity is not incidental. It’s essential for effective skin barrier formation, enzyme activity, microbial balance, and the control of inflammation.3 Healthy adult skin can have a surface pH between 4 and 5.83 , with consensus being that healthy facial skin should be around 4.5–5.5.4

PH LEVELS ACROSS THE LAYERS OF THE SKIN

But just underneath the skin’s outer layer or stratum corneum, in the living layers of the epidermis, the pH is almost neutral, around 7.4.4 So there is a steep two to three unit gradient between the acidic stratum corneum and the near-neutral deeper epidermis and dermis.4 This steep gradient is essential in several processes involved in forming and maintaining the skin barrier.5

The slightly acidic surface activates the enzymes that make ceramides, such as ß-glucocerebrosidase, phospholipase A2, and acid sphingomyelinase.5 Ceramides are the fats that seal the spaces between skin cells and form a strong, healthy barrier. When the skin surface becomes more alkaline, ceramide production drops, and the barrier weakens.5

The acidic pH is also crucial for a healthy skin microbiome. Good bacteria such as Staphylococcus epidermidis prefer a pH around 5, while harmful bacteria, including Staphylococcus aureus, E. coli, and Pseudomonas grow much better when the skin becomes more alkaline. When the pH rises, the balance of microbes shifts in favour of the harmful ones.6

Studies show that pH is the key signal that guides the final stage of skin cell differentiation. As keratinocytes move upward, they pass through three pH-defined zones: nearly neutral, mildly acidic, and strongly acidic. Each zone switches specific enzymes on or off to control filaggrin breakdown, lipid processing, and eventual corneocyte shedding.7 When the skin fails to acidify properly, these steps break down, causing abnormal skin cell differentiation, thicker skin, and weaker barrier function. So, a low, well-controlled pH is essential for skin cells to mature normally, which in turn helps the skin maintain a healthy barrier.7

CONSEQUENCES OF DISRUPTED PH

Research shows skin with a pH below 5.0 has better barrier function, hydration, and less scaling than skin with a higher pH.8 A higher skin pH has been linked to rosacea9 , acne and dermatitis.10

BALANCING PH LEVELS WITH SKINCARE

Topical skincare products have been shown to interact with the skin microbiome and change the skin pH.11 Research suggests that skincare products with a pH around 4, improve barrier function better than neutral/alkaline ones.12 Skincare with a pH up to 6 won’t harm the skin.12 This is especially important for more mature skin.12

ADVICE FOR CLINICIANS

Look for skincare products with a pH of below 5.5 to optimise skin health.11 The exception is zinc-based sunscreens, which are very difficult to formulate with a pH below 7. This can be mitigated by application of an L-ascorbic acid serum, which generally has a pH below 3. Reputable skincare companies openly disclose the pH of their products within a very narrow range, indicating tight quality control. If your chosen skincare brand does not disclose its pH, reach out to the company and Scan for references: request the information. If they either cannot provide it or give a large range eg 5-6.5, I personally would not recommend prescribing these products, especially for patients with evidence of dehydrated skin, an altered microbiome (acne, dermatitis or rosacea) or sensitive skin. .

DR GINNI MANSBERG

Dr Ginni Mansberg is a GP, TV presenter, podcaster, author and columnist. She is a physician specialising in women’s health, menopause and all things skin. She is also the co-founder and medical director of science-based cosmeceutical skincare brand, Evidence Skincare (ESK), and author of bestseller, The M Word, How to Thrive in Menopause.