Barrier damage

Anti-Pollution Matrix > Damage > Clinical > Barrier damage

Explanation

The skin represents the external protective barrier of the body. It protects the human organism from moisture loss/water loss (trans epidermal water loss, TEWL), prevents pathogenic microorganisms such as bacteria, viruses or other substances from entering the body, and generally protects against exogenous factors. In addition, it is significantly involved in temperature regulation, is a sensory organ that transmits thermal stimuli, touch and pain. Furthermore, it has secretion functions and represents an important component of the immune system.

The skin can generally be divided into three layers: the epidermis, the dermis and the subcutis. In addition, there are skin appendages such as hair, sweat and sebaceous glands, and nails.

The uppermost layer of the epidermis, the stratum corneum (SC) represents the most important barrier to the environment. This layer is composed of dead cells (corneocytes), which give the skin firmness and stability and represent the skin barrier to the outside world. The lipid layer is mainly composed of ceramides, free fatty acids and cholesterol. In addition to water, the SC also contains proteins and lipids.

Although the SC is the thinnest layer of the skin (~ 10-20 µm; consists of 12-16 cell layers on average), it represents the essential barrier to water loss (TEWL) to the outside or penetration of foreign substances of various types to the inside.

In addition, the skin has a protective acid mantle with an average pH of 4.8 - 5.5. This is a hydro-lipid film formed by sweat and sebaceous glands and consists of electrolytes, uric acid, fatty acids and urea and bactericidal peptides in addition to water. This protective acid mantle also protects the skin from dehydration.

An imbalance triggered by air pollution can result in damage to skin lipids, proteins and thus lead to damage of functional structures in the skin barrier. [1, 2, 3]. Specifically, it was found that particulate matter and UV radiation promoted the formation of protein carbonyls in the skin. Furthermore, an increase in lipid peroxidation was found after smoke exposure in keratinocytes [4].

 

Effects on the skin

If the skin barrier is damaged, there may be increased water loss (TEWL), and the pH of the acid mantle may also change and corneal moisture may decrease. Permeability of the barrier lipids may increase due to direct damage to keratinocytes and corneocytes.

A disturbed skin barrier may result in an increased uptake of, for example, toxic air pollutants into the skin with the possible subsequent reactions (e.g. inflammation). Sunlight can further increase the damaging effects of air pollutants [1, 2, 3].

 

Measures

A good skin cleansing and skin care routine that provides the skin with sufficient moisture and lipids to keep it supple, with the aim of sustainably protecting and strengthening the skin barrier.

 

Impact detection methods

• Corneometry
• TEWL (Trans epidermal water loss)
• Skin surface pH

 

References

[1] C.M. Chuong, B.J. Nickoloff, P.M. Elias, L.A. Goldsmith, E. Macher, P.A. Maderson, J.P. Sundberg, H. Tagami, P.M. Plonka, K. Thestrup-Pederson, B.A. Bernard, J.M. Schroder, P. Dotto, C.M. Chang, M.L. Williams, K.R. Feingold, L.E. King, A.M. Kligman, J.L. Rees, E. Christophers, What is the 'true' function of skin?, Exp Dermatol, 11 (2002) 159-187, doi: 10.1034/j.1600-0625.2002.00112.x
[2] R. Marks, The stratum corneum barrier: the final frontier, J Nutr, 134 (2004) 2017S-2021S. https://doi.org/10.1093/jn/134.8.2017S
[3] Schaefer H, Redelmeier T. 1996. Skin barrier. Basel: Karger, https://doi.org/10.1159/000425547
[4] F. Richard, T. Creusot, S. Catoire, C. Egles, H. Ficheux, Mechanisms of pollutant-induced toxicity in skin and detoxification: Anti-pollution strategies and perspectives for cosmetic products. Ann Pharm Fr (2019) 77:446-459. DOI: 10.1016/j.pharma.2019.07.001