SKIN PROTECTION 105
How to support the skin’s own protective strategies
Gabrielle Moro - Codif Technologie Naturelle, France
Often described as the skin’s barrier function, the epidermis is considered to be the first protection of our body against external factors. For a long time, the cornified layer, which is the upper layer of the epidermis, has been considered as the first line of defence of the skin. Although the cornified layer is the outer layer of the epidermis, it is no more considered as the outer layer of our skin. On its surface, a homemade biofilm actually ensures the first protection of our skin, this biofilm is called hydrolipidic film and hosts skin microbiota. The hydrolipidic film (HLF) is a protective film that covers the entire surface of the skin. This is an emulsion of water and lipids which acts to lock in moisture and as a defence against non-resident bacteria. It mainly consists of perspiration, water, sebum, and lipids. Its alteration is characteristic of lipid dry skins or essential fatty acids deficient skins, which are literally stripped due to limited sebaceous gland excretions. In this case skin takes a reactive appearance, it can appear hot/burning, possibly itchy; it shows signs of roughness and dullness. All these factors indicate loss of structural integrity.
a
Factors that can impair the HLF are numerous
Genetics first; some people are predisposed to this; this is the case of naturally very dry skins. Then ageing, which is often characterised by a lower sebum production. In our daily routine, products which do not suit our skin type or soap cleansing can also impair the HLF. HLF is indeed part of the components that we remove daily from our skin by cleansing. The excessive removal of the HLF strips the epidermis of its protection. Environmental factors can also impair the
% in
epidermal lipids
Glycerides
Free fatty acids Wax esters Squalene
Cholesterol esters
Cholesterol
30-35 8-16
% in
sebum 30-50
15-30 26-30 12-20
15-20 20-25
3-6 1.5 – 2.5
Table 1 : Composition of the lipid part of hydrolipidic film.5
b
HLF. Every day exposure to environmental factors directly impacts our protective HLF. For example, free radicals generated by UVs trigger a peroxidation reaction of epidermal lipids. This reaction is the first step of a succession of oxidations and chain reactions within the epidermis, and among them an imbalance of HLF quality. Car exhaust fumes will directly impact skin inflammation rate but also dehydration,1
thus decreasing water
available for HLF emulsion. If the HLF fails to do its job then a domino effect occurs which will lead to more serious skin conditions and complaints. Among them, another skin defence system will be impacted by HLF imbalance: skin microbiota. HLF is indeed the natural medium of our microbiota. It maintains skin’s acidity level and nutrients to cultivate our microbiota; it also maintains water and more precisely free water which is different from skin moisturisers and essential for bacterial growth. Finally, it provides carbon and nitrogen sources. In return the skin’s resident bacteria act as cleaners, preventing undesirable microorganisms from developing, and defending against non-resident bacteria. Over the last few months microbiota has become our new vital organ, changing with our age, lifestyle, environment and so on. As microbiota science is still in its infancy, the data varies constantly but always in similar proportions; we are said to be made up of 30% human cells, and 70% micro-organisms. Microbiota entered the cosmetic market through numerous studies on symbiosis between skin microbiota and epidermis to find an effective solution to skin diseases. Indeed over the past 30 years, the cases of pediatric eczema or atopic dermatitis have almost tripled.2 Today this is 50% of women that declare having sensitive or reactive skins,3
as a
Figure 1: Visualisation of sebum production in green fluorescence by human sebocytes cultivated in dry skin model conditions, without (A) and with 0.02% Wakapamp (B) for 8 days.
April 2018
result consumers are more and more concerned about protecting their skin, preserving their skin’s health; and finally
PERSONAL CARE EUROPE
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