Soap is one of the most popular face cleansers.
However, high pH soap damage the skin barrier.
This article will discuss:
- What is soap?
- The problem with soap
- The high pH of soap can damage the skin barrier
- What is a syndet bar and syndet liquid cleanser?
- Summary
- References
What is soap?
Soaps are available as bars or liquids.
Soap is created when a fat is mixed with a base (alkali) resulting in a fatty acid salt with detergent properties (Willcox et al, 1989).
Modern soaps are a blend of animal fats (tallow) and/or vegetable and nut oils, and fatty acids derived from these products, in a ratio of 4:1 of fats to alkali (Draelos et al, 2018).
Changing the amount of fats modifies the cleansing ability of the soap.
For example, adding more fat or oils results in “superfatted” soaps, which are praised for their cleansing “mildness.” It is the excess fatty acid that reduces the ability of the cleanser to remove lipids from the skin barrier; thus, these products are marketed as “sensitive skin” cleansers (Draelos et al, 2018).
The problem with soap
Soaps can damage the skin barrier.
Soaps typically have a high pH of 9-10, and soap can disrupt your skin barrier.
The pH of the skin is generally in the range 4.5 to 6.5.
The pH numbers refer to the acid, neutral or alkaline nature of the skin. The number is a range from 1 to 14, where 1 is highly acidic and 14 is highly basic (or alkali).
The pH at the surface of healthy adult human skin is slightly acidic, around pH 5 (Schade et al, 1928; Lambers et al, 2006).
A proper skin pH is important to maintain healthy skin conditions, cutaneous homeostasis (Flur et al, 2002, Rippke et al, 2002; Parra et al, 2003; Hachem et al, 2003) and microbial flora (Leyden et al, 1987, Lambers et al, 2006).
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 damage the skin barrier
Soap can damage the skin barrier.
The high pH of soap causes swelling of the outer skin cells, which allows unwanted deeper penetration of the soap into the skin possibly causing irritation and itching (Prottey et al, 1975).
Soap can also bind to proteins in your skin cells 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).
Finally, the ability of the cleanser to rinse completely from the skin is important.
As all soaps are irritating, they must not remain on the skin any longer than necessary. In cases where patients have mistakenly thought a moisturizing cleanser should remain on the skin to maximum benefit, irritant contact dermatitis has occurred (Draelos et al, 2018).
What is a syndet bar and syndet liquid cleanser?
Syndets, which are short for "synthetic detergents" are the most common cleanser formulations available today (Draelos et al, 2018).
Syndets are made by combining different surfactants.
Different types of surfactants are used individually or in combination with each other. Non-ionic surfactants are the mildest for dry skin (Mijaljica et al, 2022).
Syndets have a lower alkaline pH, compared to soaps, and result in less removal of intercellular lipids from the skin.
Soaps typically have a pH of 9-10 while syndets are formulated at a pH of 5.5-7, closer to the natural neutral skin pH (Wortzman et al, 1991).
It is possible to combine both soap and syndet cleansers into a formulation known as a "combar", short for 'combination bar', providing better cleansing with less lipid disruption of the skin barrier (Draelos et al, 2018).
Liquid cleansers have a composition similar to bar cleansers, except they can be poured from a bottle.
To the syndets, lipophilic moisturizing ingredients can also be added, such as petrolatum, vegetable oils, or shea butter.
A liquid cleanser can both cleanse and leave behind a moisturizing residue, which is useful for dry skin (Draelos et al, 2018).
Summary
Soap is one of the most popular face cleansers.
However, high pH soap can irritate and damage the skin barrier.
Soap should be replaced with low pH syndet bars, or other gentle cleansers that can preserve your skin barrier.
Learn more: 8 Types of Face Cleansers - Which Are Best for Cleansing Your Dry Skin?
References
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Draelos ZD. The science behind skin care: Cleansers. J Cosmet Dermatol. 2018 Feb;17(1):8-14.
Fluhr JW, Dickel H, Kuss O, Weyher I, Diepgen TL, Berardesca E. Impact of anatomical location on barrier recovery, surface pH and stratum corneum hydration after acute barrier disruption. Br J Dermatol 2002; 146: 770–776.
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.
Leyden JJ, McGinley KJ, Nordstrom KM, Webster GF. Skin microflora. J Invest Dermatol 1987; 88: 65s–72s.
Mijaljica D, Spada F, Harrison IP. Skin Cleansing without or with Compromise: Soaps and Syndets. Molecules. 2022 Mar 21;27(6):2010.
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.
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.
Willcox MJ, Crichton WP. The soap market. Cosmet Toilet. 1989;104:61-63.
Wortzman MS. Evaluation of mild skin cleansers. Dermatol Clin. 1991;9:35-44.
Yosipovitch G, Maibach HI. Skin surface pH: a protective acid mantle. Cosmet Toiletries 1996; 111: 101–112.
Author Information
Dr. Natasha Ryz is a scientist, skin care expert and an entrepreneur. She is the founder of Dry Skin Love Skincare, and she creates skincare products for beauty, dry skin and pain relief.
Dr. Ryz has a PhD in Experimental Medicine from the University of British Columbia in Vancouver, and she is a Vanier scholar. She also holds a Master of Science degree and a Bachelor of Science degree from the University of Manitoba in Winnipeg.
Natasha is the former Chief Science Officer of Zenabis Global, and she oversaw cannabis extraction, analytics, and product development. Her team brought 20 products to market including oils, sprays, vapes and softgels.
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