The Acid Mantle of Your Skin Barrier: How it Protects You

Posted by Dr. Natasha Ryz on

The "acid mantle" describes the inherent acidic nature of the outer skin barrier, also known as the stratum corneum.

The pH of the skin barrier is slightly acidic, in the range 4.5 to 6.5.

In this article, we will discuss what the acid mantle is, its purpose, and why it's important to maintain a healthy skin barrier.

    • What is the acid mantle?
    • What does pH stand for?
    • What is the pH of skin?
    • Why is the acid mantle important?
      • Skin pH maintains skin barrier
      • Skin pH protects against bad bacteria
    • What can affect skin pH?
      • The high pH of soap can disrupt the skin barrier
    • Summary
    • References
The Acid Mantle of Your Skin Barrier: How it Protects You

What is the acid mantle?

The acid mantle is a part of your skin barrier.

In 1928, the physicians Heinrich Schade and Alfred Marchionini first coined the term Säuremantel or “acid mantle” to describe the inherent acidic nature of the outer skin barrier, or stratum corneum (Schade et al, 1928).

The pH of the skin is slightly acidic, in the range 4.5 to 6.5.

The low pH level is maintained by fatty acids, sebum and sweat that is naturally made by your body (Schmid-Wendtner et al, 2006).  

The acidic pH is important in maintaining the skin's health and acts as a defense mechanism against harmful bacteria and pollutants. 

The Acid Mantle of Your Skin Barrier: How it Protects You

What does pH stand for?

The term pH is a measure of the acidity or basicity of a solution, specifically aqueous solutions.

pH stands for "potential of hydrogen" and is a representation of the concentration of hydrogen ions (protons) in a substance.

The pH scale ranges from 1 to 14, where a low pH indicates an acidic solution with a high concentration of hydrogen ions, and a high pH indicates a basic or alkaline solution with a low concentration of hydrogen ions. Neutral solutions have a pH of 7, which is considered the reference point of the scale.

The pH scale was first introduced by Danish biochemist Søren Peter Lauritz Sørensen in 1923 as a way to measure the concentration of hydrogen ions in a substance. 

It is important to note that the pH scale is logarithmic, meaning that a change of one unit on the scale represents a tenfold difference in the concentration of hydrogen ions. This means that a solution with a pH of 5 is ten times more acidic than a solution with a pH of 6, and a hundred times more acidic than a solution with a pH of 7.

The Acid Mantle of Your Skin Barrier: How it Protects You

What is the pH of skin?

The pH of the extractable water-soluble components of the skin can be measured. The skin pH and the buffering capacity of the skin surface are made up of the contributions from all the components of the stratum corneum as well as the secretions from sebaceous and sweat glands (Dikstein et al, 1994).

The pH at the surface of healthy adult human skin is slightly acidic, around pH 5, with a range of 4.5 to 6.5 (Schade et al, 1928; Lambers et al, 2006).

The Acid Mantle of Your Skin Barrier: How it Protects You

Why is the acid mantle important?

A proper skin pH is important to maintain healthy skin.

Maintaining skin pH is important, as skin pH influences skin barrier homeostasis, stratum corneum integrity and cohesion, and antimicrobial defense mechanisms. 

Your skin pH influences:

  • Skin barrier function.
  • Desquamation or shedding of skin cells.
  • Protection against pathogens "bad bacteria."

(Reviewed by Ali et al, 2013).

Skin pH maintains skin barrier

There are several key enzymes involved in maintaining the skin barrier that are impacted by skin pH.

For instance, the enzyme glucocerebrosidase with an optimum pH of 5.6 is involved in the synthesis of the most important ceramides (Schmid-Wendtner et al, 2006).

Ceramides are fats or lipids that are found in skin cells. They make up 30% to 40% of your outer skin layer, or epidermis. Ceramides are important for retaining your skin’s moisture and keeping your skin barrier healthy.

Skin pH protects against bad bacteria

For the skin's antimicrobial defence, there is an association between a lower pH level and reduced expression of bacteria proteins, in particular, those involved in adherence to the skin by bacteria Staphylococcus aureus (e.g., protein A, clumping factor B, fibronectin-binding protein A) (Leung et al, 2013)..

High Staphylococcus aureus colonization rate is shown in children and adults with atopic dermatitis (eczema). Colonization rate increases with the severity of the atopic dermatitis, and it acts as an aggravating factor exacerbating inflammation (Ogonowska et al, 2021).

Changes in the pH level toward more alkaline are one of the factors, facilitating Staphylococcus aureus colonization and growth in patients with atopic dermatitis (eczema) (O'Regan and Irvine, 2008; Proksch et al, 2008; Clausen et al, 2019). 

A higher skin pH 7.0–8.0 has been shown optimal for Staphylococcus aureus sticking to human skin cells (Mempel et al, 1998).

The Acid Mantle of Your Skin Barrier: How it Protects You

What can affect skin pH?

Many factors can affect the pH of the skin, including age, sebum, sweat, detergents, cosmetics, and irritation (Ali et al, 2013; Yosipovitch et al, 1996).

Even rinsing your skin with water alone produces an immediate but transient increase in its pH (Gfatter et al, 1997). 

The high pH of soap can disrupt the skin barrier

Soaps typically have a high pH of 9-10, and soap can disrupt the skin barrier.

The pH of the skin is generally in the range 4.5 to 6.5.

The high pH of soap causes swelling of the stratum corneum, which allows unwanted deeper penetration of the soap into the skin possibly causing irritation and itching (Prottey et al, 1975).

Soap can also binds to stratum corneum proteins further inducing swelling and hyper hydration of the skin. Following the completion of washing, the excess water evaporates leading to skin tightness and dryness because the soap binding reduces the ability of the skin proteins to hold water. This explains the reduction in skin hydration and elasticity following soap cleansing (Draelos et al, 2018).

Learn More: 8 Types of Face Cleansers - Which Are Best for Cleansing Your Dry Skin?

 

The Acid Mantle of Your Skin Barrier: How it Protects You

Summary

The pH of the skin barrier is slightly acidic, in the range 4.5 to 6.5.

The term "acid mantle" describes the inherent acidic nature of the outer skin barrier, or stratum corneum.

Maintaining skin pH is important, as skin pH influences skin barrier homeostasis, stratum corneum integrity and cohesion, and antimicrobial defense mechanisms. 

Many factors can affect the pH of the skin, including age, sebum, sweat, detergents, cosmetics, and irritation.

Soaps and cleansers that are high in pH should be avoided, as high pH soaps can irritate and disrupt the skin barrier.

References:

Ali SM, Yosipovitch G. Skin pH: from basic science to basic skin care. Acta Derm Venereol 2013; 93: 261–267. 

Ananthapadmanabhan KP, Mukherjee S, Chandar P. Stratum corneum fatty acids: their critical role in preserving barrier integrity during cleansing. Int J Cosmet Sci. 2013 Aug;35(4):337-45. 

Chan A., Mauro T. (2011). Acidification in the epidermis and the role of secretory phospholipases. Dermatoendocrinology 3 84–90. 

Clausen M. L., Edslev S. M., Nørreslet L. B., Sørensen J. A., Andersen P. S., Agner T. (2019). Temporal variation of Staphylococcus aureus clonal complexes in atopic dermatitis: a follow-up study. Br. J. Dermatol. 180 181–186.

Dikstein S, Zlotogorski A: Measurements of skin pH. Acta Derm Venereol (Stockh) 1994;(suppl 185):18–20.

Draelos ZD. The science behind skin care: cleansers. J Cosmet Dermatol. 2018 Feb;17(1):8-14.

Gfatter R, Hackl P, Braun F. Effects of soap and detergents on skin surface pH, stratum corneum hydration and fat content in infants. Dermatology 1997; 195: 258–262.

Hachem JP, Crumrine D, Brown BE, Feingold KR, Elias PM. pH directly regulates epidermal permeability barrier homeostasis, and stratum corneum integrity/cohesion. J Invest Dermatol 2003; 121: 345–353.

Lambers H, Piessens S, Bloem A, Pronk H, Finkel P. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. Int J Cosmet Sci 2006; 28: 359–370.

Leung D. Y. M. (2013). New Insights into atopic dermatitis: role of skin barrier and immune dysregulation. Allergol. Int. 62 151–161.

Leyden JJ, McGinley KJ, Nordstrom KM, Webster GF. Skin microflora. J Invest Dermatol 1987; 88: 65s–72s.

Mempel M., Schmidt T., Weidinger S., Schnopp C., Ring J., Abeck D., et al. (1998). Role of Staphylococcus aureus surface-associated proteins in the attachment to cultured HaCaT keratinocytes in a new adhesion assay. J. Invest. Dermatol. 111 452–456. 

Milstone LM. Epidermal desquamation. J Dermatol Sci. 2004 Dec;36(3):131-40.

Ogonowska P, Gilaberte Y, Barańska-Rybak W, Nakonieczna J. Colonization With Staphylococcus aureus in Atopic Dermatitis Patients: Attempts to Reveal the Unknown. Front Microbiol. 2021 Jan 11;11:567090.

O’Regan G. M., Irvine A. D. (2008). The role of filaggrin loss-of-function mutations in atopic dermatitis. Curr. Opin. Allergy Clin. Immunol. 8 406–410.

Pappas A. Epidermal surface lipids. Dermatoendocrinol. 2009 Mar;1(2):72-6.

Parra JL, Paye M. EEMCO Group. EEMCO guidance for the in vivo assessment of skin surface pH. Skin Pharmacol Appl Skin Physiol 2003; 16: 188–202. 

Proksch E., Brandner J. M., Jensen J. M. (2008). The skin: an indispensable barrier. Exp. Dermatol. 17 1063–1072.

Prottey C, Ferguson T. Factors which determine the skin irritation potential of soaps and detergents. J Soc Cosmetic Sci. 1975;26:29- 46.

Rippke F, Schreiner V, Schwanitz HJ. The acidic milieu of the horny layer: new findings on the physiology and pathophysiology of skin pH. Am J Clin Dermatol 2002; 3: 261–272. 

Schade H, Marchionini A. Der s€auremantel der haut (nach Gaskettenmessung). Klin Wochenschr 1928; 7: 12–14. 

Verdier-Sévrain et al. (2007). Skin hydration: a review on its molecular mechanisms. Journal of Cosmetic Dermatology, 6, 75–82. 

Schmid-Wendtner MH, Korting HC. The pH of the skin surface and its impact on the barrier function. Skin Pharmacol Physiol. 2006;19(6):296-302.

Yosipovitch G, Maibach HI. Skin surface pH: a protective acid mantle. Cosmet Toiletries 1996; 111: 101–112. 

Dry Skin Skin Barrier Skin Science

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