Improper skin cleansing may disrupt or disturb the moisture skin barrier, affect the skin surface pH, and irritate the skin
In this blog we would like to share with you some news, new results in research related to skin cleanser and topics how improper skin cleansing may disrupt the moisture skin barrier, affect the skin pH balance and even cause skin irritation.
The human skin is one of the largest and most versatile organs of the human body. Owing to its function as a protective interface between the largely sterile interior of the human body and the highly microbial contaminated outer environment, it is densely colonized with a diverse and active microbiota. This skin microbiota is of high importance for human health and well-being. It is implicated in several severe skin diseases and plays a major role in wound infections. Many less severe, but negatively perceived cosmetic skin phenomena are linked with skin microbes, too (Egert M., Simmering R., 2016).
Why should we care about “acid mantle”?
Each cleansing agent, even normal tap water, influences the skin surface. The increase of the skin pH irritates the physiological protective “acid mantle”, changes the composition of the cutaneous bacterial flora and the activity of enzymes in the upper epidermis, which have an acid pH optimum. The dissolution of fat from the skin surface may influence the hydration status leading to a dry and squamous skin (Gfatter R., et al., 1997).
This is very interesting observation groups of authors (Lambers H. et al, 2006) regarding skin pH!
Variable skin pH values are being reported in literature, all in the acidic range but with a broad range from pH 4.0 to 7.0. In a multicenter study (N = 330), we have assessed the skin surface pH of the volar forearm before and after refraining from showering and cosmetic product application for 24 h. The average pH dropped from 5.12 ± 0.56 to 4.93 ± 0.45. On the basis of this pH drop, it is estimated that the “natural” skin surface pH is on average 4.7, i.e. below 5. This is in line with existing literature, where a relatively large number of reports (c. 50%) actually describes pH values below 5.0; this is in contrast to the general assumption, that skin surface pH is on average between 5.0 and 6.0. Not only prior use of cosmetic products, especially soaps, have profound influence on skin surface pH, but the use of plain tap water, in Europe with a pH value generally around 8.0, will increase skin pH up to 6 h after application before returning to its “natural” value of on average below 5.0. It is demonstrated that skin with pH values below 5.0 is in a better condition than skin with pH values above 5.0, as shown by measuring the biophysical parameters of barrier function, miniaturization and scaling. The effect of pH on adhesion of resident skin microflora was also assessed; an acid skin pH (4–4.5) keeps the resident bacterial flora attached to the skin, whereas an alkaline pH (8–9) promotes the dispersal from the skin (Lambers H., et al, 2006).
Skin cleansers may be an important adjunct to the regimen of those who use decorative cosmetics, have sensitive or compromised skin, or utilize topical therapies. Cleansers emulsify dirt, oil and microorganisms on the skin surface so that they can be easily removed. During cleansing, there is a complex interaction between the cleanser, the moisture skin barrier, and skin pH. Cleansing, with water, soap or a liquid cleanser, will affect the moisture skin barrier. Soap will bring about the greatest changes to the barrier and increase skin pH to critical alkaline pH.
Liquid facial cleansers are gentler, effecting less disruption of the barrier, with minimal change to skin pH, and can provide people with a cleanser that is a combination of surfactant classes, moisturizers and acidic pH in order to minimize disruption to the skin barrier (Kuehl B.L., et al., 2003).
Skin cleansers are surface-active substances (i.e., emulsifiers/detergents/surfactants/soaps) that lower the surface tension on the skin and remove dirt, sebum, microorganisms and exfoliated corneum cells in an emulsified form. The ideal cleanser should do this without irritating, damaging or disrupting the skin and the moisture skin barrier. Water alone removes approximately 65% of oil and dirt from the skin, but is less effective at removing oils of cosmetic import and some environmental insults. Soaps are the oldest surfactants, and are chemically defined as the alkali salt of fatty acids with a pH of 9.5-10. The acid mantle of the skin plays an integral role in skin barrier function as well as regulating bacterial flora.4 Studies have shown that skin barrier regeneration/repair proceeds more slowly at neutral pH (7.2) than at physiological pH 5.5. Cleansers may also cause irritant or allergic contact dermatitis and this effect is enhanced if the skin barrier is compromised.
What is the best choice if you use commercial brand cleansers?
The choice of facial cleanser is important for people with normal skin, as well as for those people with sensitive skin and skin diseases such as atopic dermatitis, acne vulgaris. Liquid facial cleansers are the best choice for facial cleansing as they have an acidic pH, moisturizers and high rinsibility. Within the liquid cleanser category, the least irritating cleanser will contain non-ionic/silicone-based surfactants combined with moisturizers, as they will cause the least disruption to the moisture skin barrier and the normal skin flora.
- Egert M., Simmering R., The Microbiota of the Human Skin. Adv. Exp. Med. Biol. 2016;.902:61-81.
- 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(3):258-62.
- Lambers H., Piessens S., Bloem A., Pronk H. and Finkel P., Natural skin surface pH is on average below 5, which is beneficial for its resident flora. International Journal of Cosmetic Science, Volume 28, Issue 5, pages 359–370, October 2006.
- Kuehl B.L., Fyfe K.S., Shear N.H. Cutaneous cleansers. Skin Therapy Lett. 2003 Mar; 8(3): 1-4.