Having freckles is genetic and is related to the presence of the melanocortin-1 receptor MC1R gene variant, which is dominant. Freckles are often found in people with fair hair such as blonde, strawberry blonde, dishwater blonde, or most commonly red hair. 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 and more numerous.
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. However due to the debate about the safety of sunscreen, protective clothing should be the preferred method.   Sunscreens and Cancer by Hans R Larsen
Two 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 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.
- 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): 1205–1212. doi:10.1016/j.freeradbiomed.2006.06.011.
- Garland C, Garland F, Gorham E (1992). "Could sunscreens increase melanoma risk?". Am J Public Health. 82 (4): 614–5. PMID 1546792.
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