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- $Unique_ID{BRK01295}
- $Pretitle{}
- $Title{What Causes a Tan?}
- $Subject{sun tan dangers cancer skin subcutaneous tissue burn ultraviolet UV
- radiation rays erythema prostaglandin melanin pigment uva uvb epidermis
- melanoma sunscreens protection factor spf sun's tanning tanned cancers burns
- light ray pigments epidermal melanomas sunscreen}
- $Volume{L-20}
- $Log{
- Anatomy of the Skin*0006701.scf}
-
- Copyright (c) 1991-92,1993 Tribune Media Services, Inc.
-
-
- What Causes a Tan?
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-
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-
- QUESTION: While everyone now is warning against the dangers of a sun tan, I
- still don't understand what causes a tan? If the body produces this naturally
- isn't it a good thing? While you're at it, perhaps you can explain just what
- causes a sun burn as well? I know that isn't too good for you.
-
- ------------------------------------------------------------------------------
-
- ANSWER: Obviously a sun burn with its painful consequences is something to
- avoid, and can rapidly change a fun weekend into something far less enjoyable.
- Actually there are four effects upon the skin from exposure to the ultraviolet
- (UV) radiation in the sun rays, all of which attempt to reduce the injurious
- effects of the sun's rays. They are erythema, short-term tan, common tan, and
- delayed thickening of the skin. Erythema is the name given to the red flush
- that occurs to the skin after exposure to sun rays (as well as a variety of
- other causes). A substance called prostaglandin is released by the tissues
- which causes the capillaries in the skin to dilate (open), fill with more
- blood and give the red coloring to the skin. This is an attempt to protect
- the skin and reduce the damage from the sun's rays. It comes on from 2 to 12
- hours after exposure and its severity is related to the amount of exposure. A
- short-term tan is caused by ultraviolet A rays, is created by the oxidation of
- the melanin (pigment) in the skin and fades away in a day or two. The common
- tan takes several days to develop, and is caused by the production of more
- pigment in the skin as a response to the sun's ultraviolet B (UVB) rays,
- pigment that acts as a protection for the skin the next time it is exposed to
- the sun. Over a period of time, perhaps several months, the upper layers
- (epidermis) of the skin thicken. These thick skin layers can also absorb the
- UVB rays, and reduce the amount of harmful radiation that reaches the lower
- (basal) layer of the skin. A word about protection. Of the 1 million new
- cancers that are diagnosed each year, about 30 percent occur in the skin, and
- are thought to be provoked by chronic exposure to UV radiation. A person with
- a history or more than six serious sunburns in a lifetime is 2.4 times more
- likely to develop a melanoma, a cancer that spreads rapidly through the body
- and which can be lethal. If exposure to the sun can't be controlled, be sure
- to apply sunscreens with a sun protection factor (SPF) of at least 15 to cut
- down your exposure to these potentially harmful rays.
-
- ----------------
-
- The material contained here is "FOR INFORMATION ONLY" and should not replace
- the counsel and advice of your personal physician. Promptly consulting your
- doctor is the best path to a quick and successful resolution of any medical
- problem.
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-