Issue link: https://www.ascpskindeepdigital.com/i/1481047
70 ASCP Skin Deep Autumn 2022 U UNDERSTANDING pH IS INTEGRAL to our work as estheticians, not only because of its importance to overall skin health, but also because of the role it plays in the pathogenesis of several skin diseases. 1 The primary manifestation of many skin issues is a compromised skin barrier due to an imbalance of the pH. This means that maintaining the proper pH to preserve the integrity of the skin barrier is a primary responsibility of skin care professionals. The skin barrier, known as the extracellular matrix (ECM), provides the skin with its major hydration properties. 2 This complex network of proteins that comprise the ECM has lately been de ned as the matrisome. 3 The skin's moisture barrier exists in the epidermal barrier, primarily within the stratum corneum. This barrier has many important functions, including maintaining the permeability barrier by monitoring water content; acting as an antimicrobial and immune response barrier to outside invaders such as microbial organisms; being a photo-protection barrier to help mediate the e ects of ultraviolet (UV) light exposure; and mitigating the e ects of oxidative stress by providing an antioxidant barrier. By maintaining proper water balance within the skin cells and mitigating environmental and microbial stresses, the stratum corneum sustains normal sloughing of skin cells and sustains the skin's elasticity. 4 Acidic pH of the skin surface has been recognized as a regulating factor for the maintenance of the stratum corneum's homeostasis and barrier permeability. 5 The chemical barrier, or acid mantle, has only recently been recognized as a separate level of the skin barrier that includes factors that contribute to the acidic surface pH and the natural moisturizing factor (NMF). The NMF of the skin is created from proteolysis, the breakdown of proteins or peptides into amino acids by the action of enzymes of the epidermal laggrin. 6 Filaggrin plays an important role in the skin's barrier function, binding structural proteins in the skin's outermost skin cells to create a strong barrier. 7 In addition, processing of laggrin proteins not only leads to production of molecules that are part of the skin's NMF (which is necessary for the stratum corneum hydration maintenance), but also contributes to the skin's overall pH. THE pH SCALE As a reminder, pH stands for "potential hydrogen" and is a unit of measurement that indicates whether a substance is acidic, neutral, or alkaline. Alkaline is sometimes called "base." Just as degrees measure temperature and inches measure distance, pH measures the amount of acid or alkali in a water-based solution. Only solutions containing water and/or those that dissolve in water can have an acidic or alkaline nature. A solution is acidic or alkaline depending on the number of positive hydroxide ions or negative hydrogen ions it contains (an ion is an atom that has gained or lost electrons). If a solution has more positive hydrogen ions than negative hydroxide ions, it is acidic. If it has more negative hydroxide