Page 69 -- SKIN AND AGING

Skin cell regeneration

    With increasing age, the skin's cell renewal process becomes less efficient. Tissue repair and cell regeneration slow down. The amount of natural moisture present in the skin is reduced. Because collagen production is less, the skin becomes thinner and loses its flexibility.

Changes in the protective function

The most obvious sign of intrinsic aging is a decrease in the overall thickness of the epidermis as a whole, with a reduction in the number of cell layers. The number of cells in the stratum corneum does not diminish with age, however; this is important, because of the vital role of this layer as the skin barrier. On the other hand, the numbers of melanocytes and other cells do decrease with age. So do the numbers of the Langerhans cells, which are involved in the body's response to allergens (see page 40). This could be one reason why people tend to experience fewer allergic reactions as they get older.
    The rete pegs become less prominent, and the junction of the dermis and epidermis becomes flattened (see page 10). This means that the epidermis is not so securely held down, and becomes more vulnerable to damage by friction.
    Metabolism in the skin (as everywhere else) slows down. So too does the rate at which epidermal cells are produced, which may interfere with wound healing. The time necessary to repair the stratum corneum barrier increases considerably with age: the replacement of skin cells takes about twice as long for people over 75 as for those around 30.
    Although the sebaceous glands themselves do not change much with increasing age, sebum production declines in many older people, especially after the age of 70, though in some the glands on the face actually enlarge in extreme old age.
    With age, the number of active sweat glands falls and their output of sweat decreases too. As a result, perspiration is less in elderly skin. This explains why older people often find it hard to adapt to hot weather.
    Most older people have a dry skin and therefore have a special need to avoid the over-use of harsh soaps and detergents, in order to prevent problems associated with dryness. Aged

skin retains its fundamental ability to control water loss, but may partially lose this ability if the stratum corneum barrier becomes damaged by physical or chemical agents. Many substances will penetrate aged skin more easily than young skin.

The sun

The sun is the source of all life on Earth. Heat, light and warmth from the solar furnace sustain us all. There is a price to pay, however: the cumulative effects of invisible rays on our skin.
In parts of the world where the sun is very strong the local people usually avoid exposure, particularly when the sun is high in the sky. For