Skin pH and the acid mantle
Any pH below 7 is acidic and above 7 is basic/alkaline. Our skin surface needs a pH of around 5 to function best.
Chase Kempinski, PhD (chase@tritera.co)
We have noticed more skincare products stating that they restore or support the “acid mantle”, which stimulated our curiosity regarding this term. It was first used by German scientists in 1928 and subsequent work by other researchers indicated that certain skin pathologies caused by bacteria seemed to be correlated to changes in the skin pH, specifically, the skin becoming more alkaline (i.e. increased pH, see pH scale figure) (1). It is sometimes defined as an acidic layer that protects the outermost portion of the skin, which while easy to conceptualize, is not exactly accurate. The skin’s most exterior layer, the stratum corneum (SC), is comprised of cells that were alive deeper in the epidermis but have become non-living by the time they have migrated up to the SC. They continue to migrate to the outermost portion where they eventually are sloughed off. The release of these cells is carefully choreographed to maintain the appropriate thickness of the SC, providing optimal protection of the layers below.
In a previous post, we mentioned how the lipids of the skin (including squalene) act as the “mortar” between the skin cells (the “bricks”). One can imagine that this mortar must be sufficiently dissolved to allow the non-living cells to release from the SC at the right time (2). There are several mechanisms by which this occurs, it includes enzymatic processing of the skin lipids and cleavage of the exterior proteins that hold the cells together. The pH in the SC plays a critical role in regulating this process. If the pH is elevated, lipid processing is disrupted and the proteins which bind the SC cells together are degraded (3). This leads to a thinner SC layer which cannot sufficiently protect the layers below.
How does the pH of the SC get disrupted?
The pH of the SC increases as we age. While the skin of individuals aged 13-21 have a skin pH around 5, the skin of those aged 51-80 has increased to around 5.5 (3). While this may not seem like a large difference, it is important to note that the pH scale is logarithmic. This means that the difference between pH 5 and 6 is a factor of ten.
The use of certain products which strip away the important oils of the SC can also contribute to increased skin pH. Typical cleansing soaps are naturally alkaline which can disrupt the skin pH. This is partly why some of these dry out the skin so much (think “dishpan hands”). Astringent or alcohol-containing products can also strip away the important oils of the SC, leading to similar problems.
What is the best way to protect the skin’s pH?
There is evidence that using products that are more acidic helps maintain the acid mantle and provides protection against inflammation. Thus, using products that are pH-balanced for the skin can help support this important function. Several beauty companies offer pH-balanced cleansers (Puracy Body Wash), and there are some available from big-box store brands (Eucerin Soft Shower). Using oil-based cleansers is another great way to help protect the natural composition of the oil on our face. Tritera’s Cleansing Oil is a great example.
You can help supercharge repair of this barrier by using products that contain gentler alpha hydroxy acids, like lactic acid. This should be followed up with a product that helps replenish the skin’s balance. The best way to have healthy skin is to support its natural functions. The Optimal Antioxidant Serum we developed uses plant-based biocompatible oils to do just that—and has an equivalent pH of ~5! We think you’ll agree that it offers excellent moisturization, protection, and rejuvenation for balanced skin.
References
1. C. Surber, P. Humbert, C. Abels, H. Maibach, The Acid Mantle: A Myth or an Essential Part of Skin Health? Curr. Probl. Dermatol. 54, 1–10 (2018).
2. P. M. Elias, Epidermal Lipids, Barrier Function, and Desquamation. J. Invest. Dermatol. 80, S44–S49 (1983).
3. E. H. Choi, et al., Stratum corneum acidification is impaired in moderately aged human and murine skin. J. Invest. Dermatol. 127, 2847–2856 (2007).
