|MadSci Network: Medicine|
Skin color is influenced by three substances: hemoglobin, carotene, and, most important, the pigment melanin. Your entire epidermal area (your skin) contains some portion of a pigment called melanin. Melanin is nature's substance, which gives your skin and hair its color. Melanin is present in the iris of the eye and may be found in the sclera (white part of the eye). The powerful thing about melanin, is that it provides more benefits to you than adding color to the skin, hair and eyes. Nature has provided you with its most powerful ultraviolet (UV) protection against the harmful rays of the sun. It is nature's own sunblocker. The idea is deeply entrenched that melanin evolved primarily as a sunscreen. There is a north-side gradient in skin color. Darkly-pigmented races are clustered in the sunny tropics. Light-skinned people inhabitat foggy northern climates. Skin cancers are rare in African American people and quite uncommon in moderately pigmented Asiatic people. Photoaging, the actinically-induced appearance of premature aging, (dermatoheliosis) is scarcely noticeable in older African Americans. Wrinkles are minor or absent until later in on in the aging process. Very simply, sunburn and UV light can damage your skin, and this damage can lead to skin cancer. The effect UV light has on your skin is dependent both upon intensity and the duration of your exposure. How your skin reacts to the amount of exposure received is related to your genetic background. Even if you rarely burn, sensitive areas such as your lips, nose, palms of the hands and soles of the feet should be protected, in addition to the exposed areas of the skin. It is well-established in science that the incidence of melanoma and other cancers of the skin is on the rise (more than 800,000 new cases per year), and that solar radiation, particularly that in the UV range, is a major causative factor. In this regard, individuals with high skin melanin content are less likely than those with lower melanin content to suffer from skin cancers (basal and squamous cell carcinomas, melanomas) and other solar-induced damage (wrinkling, solar lentigines). What is Melanin? Melanin is not a single compound. Melanin refer to a class of compounds which are defined in the Merck Index as the pigments responsible for the color of skin, hair, feathers, fur, and soil. Melanin are highly irregular polymers produced in the form of granules which may be bound to protein material. Some classes of natural melanins include allomelanins, phaeomelanins, and eumelanin. However, eumelanin is the predominant epidermal melanin and is discussed here. Sunlight Your Skin's Worst Enemy Melanin particles both scatter and absorb ultraviolet and visible light smoothly over a broad spectral range. In spite of all the warnings, people don't take sunburn seriously. Every sunburn is an injury, and injuries are cumulative over the years. During the tanning process the sun stimulates the melanocytes to produce and liberate more melanin for skin protection. But until the melanin reaches the skin's surface and can protect you, the skin is left vulnerable and can be heavily damaged and burned. Sunlight, especially its UV-part, supported by infrared, is the notorious enemy of the skin. Every sign of aged skin is supported by sunlight: blemished and blotchy, loose and inelastic, rough and wrinkled skin. These same rays have been implicated in causing cataracts of the eyes. Today, we also know that the skin plays an important role in the immunological defense of the body. Sunlight has positive and negative effects. A balanced protection against these rays is very important. UVR may be present at unsafe levels even on cloudy days. Since skin cancer rates correlate inversely with pigment, it is generally assumed that melanin is photoprotective. Melanin is generally thought to be photoprotective since skin cancer risk is inversely proportional to degree of skin pigmentation. To look at the undisputed scientific benefits of melanin, we must look at the effects of what naturally occurring melanin has on people. African Americans do sunburn and seem to be clinically exempt from the well know signs of premature skin aging as seen in White Americans. African Americans rarely show deep wrinkles and the other stigmata of dermatoheliosis, depigmentations, leathery-dry skin, elastosis, sags, etc. The epidermal and dermal changes from chronic exposure to solar radiation have been thoroughly described in photoaged Whites. As far as carcinogenesis is concerned, and to some degree the connective tissue damage, Melanin or other pigments in human skin protect it. Melanin Nature's own Protection for the Skin Your skin has the ability to develop certain mechanisms of protection against the sun's rays. Science has shown indisputably that the most effective protection is the development of the skin pigment Melanin, which is induced by UVR, Melanin, a complicated biochemical reaction, is induced by UVR. There are two different types of melanin: the black brown eumelanin and the yellow/red phaeomelanin. The Function of Melanin Melanin's number one function is the protection of the skin, hair, and eyes against the damaging effects of sun's the UVR. Melanin is the umbrella of our skin; the deeper layers are also protected. One of the most important effects of melanin is the absorption of heat which works most effectively in people who have the most melanin in the skin. Melanin absorbs more or less totally over the whole range of visible and infrared light in the upper layer of the skin. The heat is transferred to the outside world. After sun exposure, biosynthesis of melanin in the skin needs 3-8 days to develop. There is no protection in the decisive first days, persons with Light skin produce very little melanin. They have no effective UV protection. Another huge plus for melanin is that it is a effective neutralizing agent for free radical scavengers--molecules which are harmful to the human body. Scientific information was obtained from the book: Melanin: Its role in human Photoprotection, Editors: Lisa Zeise, Miles R. Chedekel, and Thomas B. Fitzpatrick. June Wingert RM(ASM) Center for Comparative Medicine Department of Pathology Baylor College of Medicine Houston, Texas
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