Concept of skin aging
The skin is a unique organ, which reflects the inevitable changes occurring in the body’s aging process. It is the body’s dynamic interface with the environment and as such its roles include barrier function, mechanical protection, wound healing, immune surveillance, thermoregulation, and sebum production, to mention a few. All these functions decline with age. Aging of the skin is a complex process, associated with morphological and chemical changes, dictated by an inherent genetic program and accelerated by environmental damage to genes and their protein products. Through structural and molecular degradation, aging causes a functional deficit in the skin resulting in clinical changes, including wrinkling, colour changes (dyspigmentation), laxity and no-elasticity [5, 6].
Two independent processes govern skin aging, the intrinsic and the extrinsic aging of the skin.
Intrinsic aging, also known as the natural aging process, is the slow irreversible degeneration of tissue, which affects almost all body organs. Usually beginning in our mid-20’s, intrinsic aging is a continuous SkinCell PRO process, which by definition, is inevitable and as such is not subject to manipulation through changes in human behaviour. It is genetically programmed and causes structural and functional changes in all layers of the skin. Although it begins in the mid-20’s the signs of intrinsic aging are not usually visible for decades [7-9].
Intrinsic aging produces lines and wrinkles, age spots, splotches and pigmentation problems, broken capillaries, dull skin texture and colour, and other skin flaws. Apart from these, intrinsic aging may cause a previously attractive mole or birth mark to change into an unattractive protrusion or a once unnoticeable scar may become more apparent when wrinkles form around it. The production of collagen within the skin is slowed and elastin, a protein constituting the basic substance of elastic tissue, which enables the skin to snap back into place on pulling, becomes less “springy”.
Epidermal turnover (turnover of new skin cells), which takes about 28 days in young adults requires about 40-60 days in the elderly. This slower turnover results in a thinning of the epidermis, which gives aged skin a translucent appearance, as well as adversely affecting skin barrier function and repair, and cell exfoliation. Intrinsic aging causes a decrease in subdermal (beneath the skin) fat tissue, which contributes to wrinkling and sagging of the skin, making the skin more susceptible to trauma and bruising. Although it causes a number of structural changes, the effects of intrinsic aging are mostly functional, with only minor impacts on skin appearance (as previously mentioned) – fine wrinkling, dryness, and thinning. The genetic program of intrinsic aging differs in each individual both in terms of rate and severity of effect [8, 10, 11].
Extrinsic aging is generally caused by external factors introduced to the body, such as smoking, excessive alcohol consumption, poor nutrition, pollution, harsh weather and chronic sun exposure (photoaging). Other factors include repetitive facial expressions, gravity and sleeping positions. Of all these external factors, sun exposure is considered to be by far the most significantly harmful to the skin and according to Baumann (2007) 80% of facial aging is believed to be due to chronic sun exposure [8, 9].
1. Sun exposure (Photoaging)
The human skin is exposed to UV and infrared radiation practically everyday and without protection from the sun’s rays, a few minutes of exposure each day over the years can cause noticeable changes to the skin as the skin loses the ability to repair itself and as such, the damage accumulates. The clinical manifestation of photoaging depends on skin type, skin colour and the history of long-term or intense sun exposure. An individual with fair skin with a history of sun exposure will develop more signs of photoaging than a dark skinned individual. For individuals with the darkest of skins, the signs of photoaging are often limited to fine wrinkles and complexion marked with spots or blotches of different shades or colours. It has been shown that repeated ultraviolet exposure damages the skin by breaking down collagen, impairing the synthesis of new collagen and attacking elastin, thereby causing immense damage. Photoaging is characterised by coarse, deep, severe wrinkling as well as pigmentary changes on exposed areas such as the face, neck and forearm. Losses in skin tone and elasticity, increased skin fragility, and benign lesions are also observed in skin affected by photoaging [8-10].