The skin, like any organ, is subject to ageing. Intrinsic, genetically programmed ageing and extrinsic ageing under the influence of many environmental factors and lifestyle.
With age the cells in the skin progressively lose their activity and the functioning of the skin changes. So to put it simply:
- The cells renew themselves less quickly, the keratinocytes in the epidermis produce fewer NMFs and lipids, reducing superficial hydration. They will then accumulate on the surface and are removed (desquamate) less effectively: the complexion becomes dull and the skin dry and rough.
- Secretions from the sebaceous and sweat glands decrease, generating a depleted hydrolipidic film which accentuates the superficial dehydration. The skin becomes tight and feels less supple.
- The glycoaminoglycans, including hyaluronic acid, renew less and the renewal is not of such good quality. Their increased degradation by oxidative stress causes reduced hydration of the dermis and therefore the epidermis. The skin becomes finer, ages, and wrinkles appear.
- In the dermis a reduction in collagen and elastin fibres is observed together with disorganisation and increased degradation of these fibres. The skin loses its elasticity and firmness and wrinkles get deeper.
Finer and less well moisturised, the skin is less supple. The superficial protection against external aggressions is less efficient.
It is due to many external factors such as UV, pollution, smoking, wind, and stress. These factors are responsible for increased oxidative stress and accentuate the molecular processes involved in intrinsic ageing. So the UV rays weaken the skin cells, smoking increases the degradation of the fibres and GAGs in the dermis and epidermis, the wind and too alkaline or repeated washing dry out the skin by altering the hydrolipidic film. The modified superficial pH does not play its role of defence against microbial infectious aggressions so well.
Extrinsic ageing therefore accelerates intrinsic ageing.
* Oxidative stress: imbalance between the increased production of free radicals and reduced capacities of our bodies to neutralise them. This “over-production” is partly linked to age and strongly linked to external factors such as UV rays, cigarette smoke, pollution, alcohol, overwork, etc. The free radicals, very reactive unstable oxygen-based molecules, attack the cells (by oxidation) and particularly the skin cells: lipids, proteins and GAGs.