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Sun exposure

  1. Aug 3, 2005 #1
    okay I know my the top of my head hasnt been exposed to much sun so it will burn easily since I shaved it BUT isnt it good that it gets SOME exposure to sun so that it will build resistance to it?
  2. jcsd
  3. Aug 3, 2005 #2


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    You know what would really built a resistance to sun exposure? Staying indoors. Oh and try having a whiter (oh darn whats the politically correct word.. 'lighter'?) skin - the IR rays reflect from white surfaces more compared to dark ones

    And why would a dark skin be more 'resistant' to Sun again?
  4. Aug 3, 2005 #3
    The uv light damages cells in the skin, the layer of pigment in the dead cells in the upper layer of the epidermis blocks the uv light so that it will not reach the living cells beneath it.
  5. Aug 3, 2005 #4
    okay but will me exposing the skin on the top of my head to the skin make that skin more resistant to the sun...

  6. Aug 3, 2005 #5
    Building up a "base" tan on your head will not prevent damage to your skin. My mother has skin cancer, and she tanned, as she thought wisely, a little at a time.
  7. Aug 4, 2005 #6
    Short exposure of the skin to the sun is better, but will still damage some skin cells.

    Sunlight (particularly the ultraviolet part) damages skin cells, which unfortunately can even lead to skin cancer. Blocking the light before it reaches the cells can prevent this damage. You can block the ultraviolet light with clothing or with sunscreen, but the body also has its own protection mechanism: increasing the amount of pigment (melanin) in the skin. The increased production of melanin will be induced by exposure to UV light. Obviously this does not work instantaneously. It takes some time for certain skin-cells called melanocytes to produce the extra melanin. This is why short exposure at a time is advised; it will activate the extra melanin production (giving better protection later) while minimizing the risk to the skin cells at the moment. Needles to say, you would minimize the risk more by simply avoiding contact with UV light.
  8. Aug 4, 2005 #7


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    At the same time that you are developing "protection" from the harmful uv rays, you will also be accumulating damage. Over the course of a lifetime this damage may win out and lead to the development of cancer. The most effective protection is going to be avoidance followed by blocking either by clothing or chemicals. Protection from sun damage afforded by adaptations such as increased melanin are probably more effective in the long term speaking along evolutionary lines. While it may overall protect a population of people, it will most likely not "pay off" in one person's lifetime.
  9. Aug 4, 2005 #8
    Has anyone heard of photoreactivation? It's the simple little trick plants use to protect themselves from getting "leaf cancer". The debate over UV exposure and skin cancer in humans always seems to neglect this topic.

    There have been several studies, funded by the NIH, on human photoreactivation though results are inconclusive to date. My opinion, based on the available studies, is the ambiguity in the data is is resolved if one concludes that people who have inherited the tendency to "get" skin cancer are also the most likely to have inherited photoreactivation traits. Likewise, those who are more resistant to skin cancer are less likely to be photoreactive.

    But the ones who are don't know they are, what it is or how it works so they get no benefit from it. Ignorance isn't always bliss...
  10. Aug 4, 2005 #9


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    Getting off-topic, but photoreactivation is also a method used by some bacteria (or was it viruses?...aw, crud...gotta dust off my text books) for DNA repair.
  11. Aug 4, 2005 #10


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    It's bacteria, viruse are too simple for that type of system. if I remember correctly, some repair mechanism were found using E. coli infected with phages.
  12. Aug 5, 2005 #11
    Two other points re skin cancer. There are broadly two types: melanomas and non-melanomas. Non-melanomas are caused by UV induced DNA damage, or to be more exact they are caused by unrepaired UV induced DNA damage. However, the modern success rate of simple procedures that remove them exceeds 99%.

    Melanomas on the other hand are usually lethal. Interestingly they occur most frequently on areas of the body that have received little to no sun exposure, i.e. they are not likely linked to UV exposure. In fact a study done in Cambridge reported a genetic link. So, the cloudy picture at the moment seems to indicate there is a genetic trait in some people that leads to melanomas and that it may be triggered by a chronic absence of sun exposure.
  13. Aug 5, 2005 #12
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