Skin colour depends on a natural brownish pigment called melanin. Melanin is produced by cells called melanocytes, situated at intervals between cells in the dermis. All skins rom Scandanavian pale to Ethiopian mahogany, contain the same quota of melanocytes, but the melanocyte cells of some skins are more efficient producers of melanin than others.
The function of melanin is to act as a natural sunscreen that absorbs and filters ultraviolet rays so they cannot reach and damage the dermis. Sunlight stimulates the melanocytes to produce melanin to stave off UV radiation. Consequently, people who originate from nearest the equator have the most efficient melanocytes, while those of Northern European origin have the most inefficient, and are therefore at greatest risk from sun damage. Freckles indicate unevenly distributed melanin and poor protection against ultraviolet damage.
Is It Worth Getting a tan?
Whereas moderate sunlight enables the skin to synthesize vitamin D, excessive sun is the single greatest threat to skin health. Dermatologists estimate that 80 per cent of lines, wrinkles, sagging and coarsening are directly caused by ultra- violet light. Countless comparisons between the weatherbeaten faces of octogenarians and their smoother, seldom exposed body zones show how a lifetime under the sun leaves its mark. Sunlight ages the skin and creates a potential cancer risk. it used to be thought that only the "burning" ultraviolet-B rays posed a threat. Now it is known that whereas 95 per cent of these short-wave rays are absorbed by the epidermis, 80 per cent of so-called "tanning' ultraviolet-A rays penetrate down to the dermis. Here, they undermine the skin's structure by distorting DNA and RNA at the cell's nucleus and distorting collagen and elastin arrangements. This damage is both cumulative and largely irreversible. Distorted cells reproduce inefficient mutations, resulting in an increase in the number of lines and wrinkles, a decrease in firmness and elasticity and an epidermis that no longer retains moisture as it should.
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Monday, February 2, 2009
How to Protect Your Skin from Sunlight?
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