Freckles
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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
Having freckles is genetic and is related to the presence of the melanocortin-1 receptor MC1R gene variant, which is dominant.[1] 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. [1] [1] 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.
References
See also
External links
da:Fregne de:Sommersprosseneo:Lentugo fr:Éphélide gd:Breac-sheunain is:Freknur it:Lentiggini he:נמש lb:Speechelen nl:Sproet ja:雀卵斑 nds:Sünnsprütten no:Fregnerfi:Pisama sv:Fräknar th:กระyi:זומערשפרענקלעך
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
