Freckle: Difference between revisions
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==Biology== |
==Biology== |
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[[Image:freckled.jpg|thumbnail|left|200px |Extremely freckled |
[[Image:freckled.jpg|thumbnail|left|200px |Extremely freckled kimmels. [[Predisposition]] to freckles is genetic and is related to the presence of the MC1R gene variant.]] |
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Freckles can be found on anyone no matter the background, however, having freckles is [[gene]]tic and is related to the presence of the dominant melanocortin-1 receptor [[melanocortin 1 receptor|MC1R]] gene variant.<ref>{{OMIM|266300}}</ref> The formation of freckles is triggered by exposure to [[sunlight]]. The exposure to UV-B radiation activates melanocytes to increase the melanin production, which causes freckles to become darker. |
Freckles can be found on anyone no matter the background, however, having freckles is [[gene]]tic and is related to the presence of the dominant melanocortin-1 receptor [[melanocortin 1 receptor|MC1R]] gene variant.<ref>{{OMIM|266300}}</ref> The formation of freckles is triggered by exposure to [[sunlight]]. The exposure to UV-B radiation activates melanocytes to increase the melanin production, which causes freckles to become darker. |
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Revision as of 20:17, 4 December 2008
Freckles are clusters of concentrated melanin which are most often visible on people with a fair complexion. A freckle is also called an "ephelis."
Biology
Freckles can be found on anyone no matter the background, however, having freckles is genetic and is related to the presence of the dominant melanocortin-1 receptor MC1R gene variant.[1] The formation of freckles is triggered by exposure to sunlight. The exposure to UV-B radiation activates melanocytes to increase the melanin production, which causes freckles to become darker.
Freckles are predominantly found on the face, although they may appear on any skin exposed to the sun. Freckles are rare on infants, and more common on children before puberty; they are less common on adults.
Upon exposure to the sun, freckles will reappear if they have been altered with creams or lasers and not protected from the sun, but do however fade with age in some cases. Freckles are not a skin disorder. People with freckles usually have a lower concentration of photoprotective melanin and are therefore more susceptible to the harmful effects of UV-radiation. An overexposure of UV-radiation should be avoided. Sunscreen has been suggested. [2] [3] [4]
Types of freckles
Ephelides is a genetic trait. It’s used to describe a freckle that is flat, light brown or red, and fades in the winter. Ephelides are more common in those with light complexions (although are found on people with a variety of skin tones) and with the regular use of sunblock, can be suppressed.
Liver spots (also known as sun spots and Lentigines) are freckles that sometimes do not fade in the winter. Rather, they form after years of exposure to the sun. Lentigines are more common in older people.
References
- ^ Online Mendelian Inheritance in Man (OMIM): 266300
- ^ Hanson Kerry M.; Gratton Enrico; Bardeen Christopher J. (2006). "Sunscreen enhancement of UV-induced reactive oxygen species in the skin". Free Radical Biology and Medicine. 41 (8): 1205–12. doi:10.1016/j.freeradbiomed.2006.06.011. PMID 17015167.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Garland C, Garland F, Gorham E (1992). "Could sunscreens increase melanoma risk?". Am J Public Health. 82 (4): 614–5. PMID 1546792.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Sunscreens and Cancer by Hans R Larsen
See also
