Freckle
Freckles are clusters of concentrated melanin
which are most often visible on people with a fair complexion.
A freckle is also called an ephelis.
Freckles do not have an increased number of melanin producing cells
(melanocytes). This is in contrast to lentigines
and moles.[1]
Biology
Freckles can be found on anyone no
matter their genetic background; however, the amount of freckles is genetic and is related to the presence of
the melanocortin-1 receptor MC1R gene variant.[2]
The formation of freckles is triggered by exposure to sunlight.
The exposure to UV-B radiation activates melanocytes to increase melanin
production, which can cause freckles to become darker and more visible.
Freckles are predominantly found on
the face, although they may appear on any skin exposed to the sun, such as the
shoulders. Freckles are rare on infants, and more commonly found on children before puberty.
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 fade with age in
some cases. Their intensity can be altered with citric acid. Freckles are not a
skin disorder, but people with freckles generally have a lower concentration of
photoprotective melanin and are therefore more susceptible to the harmful
effects of UV-radiation. It is suggested that they avoid overexposure and use sunscreen.[3][4]
Types
of freckles
Ephelides describes a freckle which is flat and light brown or red
and fades with reduction of sun exposure. Ephelides are more common in those
with light complexions, although they are found on people with a variety of
skin tones. The regular use of sunblock can inhibit their development.
Liver spots (also known as sun spots and lentigines)
are freckles[citation needed] that may not fade in the winter. Rather, they form after
years of exposure to the sun. Liver spots are more common in older people.
The entire wiki link with images can be found at: http://en.wikipedia.org/wiki/Freckle
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