Intrinsic factors

Intrinsic ageing is the physiological ageing linked to our heredity. Indeed, everybody has one’s own ageing clock written in one’s genetic code; this is a kind of intrinsic inheritance. This results in lifelong changes in skin aspect, texture and functioning and may be seen on the body as a whole.
Changes occur in all the skin layers: epidermis , dermis , and hypodermis.

Extrinsic factors

Extrinsic ageing is due to external causes, which may have a detrimental effect on our skin health. These are risk behaviour, such as an unhealthy lifestyle (tobacco and/or alcohol consumption or an unbalanced diet), using non-suitable or too aggressive cosmetics, and, above all, sun exposure.
Indeed, sun is a cause for a premature skin ageing, called actinic or photo-induced ageing, also known under the word: photo damage.
Due to UV radiations, free radicals are produced in larger quantities in the skin and induce damages that speed up cutaneous ageing.

Results on epidermis

When we grow older, some parameters of the appearance of epidermis change:

• The stratum corneum thickens on some areas, as renewal of cells slows down: shedding is slower, skin is coarser to the touch.
• Epidermis loses in thickness and in density.
• The number of melanocytes (the cells that produce the black molecule melanin) lowers and they are less randomly spread out on skin. One may then see areas where melanin production is unbalanced: skin is more sensitive to sun and brownish marks appear.
• Sebum production decreases. The hydrolipidic film composition is modified. Skin becomes drier, not that well nourished and moisturized.
• The number of Langerhans cells decreases, hence a disorder in its immune response.

Results on dermis

Effects of skin ageing on the dermis are listed underneath:

• A decrease of the number and size of fibroblasts, which slows down the synthesis of elastin fibers, of collagen and of glycoproteins (large molecules comprised in the fundamental substance, a kind of gel in which dermis cells are immersed).
• Water retention is lower, as the fundamental substance is slower renewed.
• Collagen fibers come apart from each other, hence a loss in firmness.
• The number and the quality of elastin fibers decrease, hence a loss in tonus and resilience.
• Vascularization of the dermis decreases, which is why older people complexion is pale.

Furthermore, dermis and epidermis are in contact through the dermis-epidermis junction, which goes thinner along the years: these two layers lose their cohesion. This thinning down is the main cause for wrinkles.

Effects of cosmetics on the epidermis

Some actions may be performed to slow down the effect of the skin growing older:

• Strengthen the hydrolipidic film to counter the diminishing sebum production ( moisturizing and nourishing).
• Exfoliation, which wipes off dead cells and renders the stratum corneum thinner.
• Use a suitable sunscreen, to protect the skin and prevent damages due to sun light.

The actions on the epidermis are superficial. Indeed, even if skin ageing is seen on this outer layer, the most dramatic damages and marks are in the dermis . Nevertheless, even if these actions on the epidermis have no effect on wrinkles or firmness, a regular moisturizing and/or anti-ageing care will help in maintaining skin in good shape by nourishing it and preventing its dehydration due to the dermis thinning.

Effects of cosmetics on the dermis

Working down to the dermis level is more difficult. Active ingredients face troubles to get to this layer. Efficiency of ingredients is therefore, more or less theoretical, even if some of them go down to the dermis .

Possible actions on the dermis are mainly stimulations or some active ingredients, as moisturizing to offset the loss of fundamental substance. Damaged cells in the dermis can almost never recover through cosmetic products; nevertheless, any preventive action to lessen damages is a good idea, such as through a healthy lifestyle and a daily moisturizing of the face and body skin.

ML