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Freckles, sometimes called ephelis, are clusters of concentrated melanin which are most often visible on people with a fair complexion. Freckles do not have an increased number of melanin-producing cells (melanocytes), but instead have cells that overproduce melanin granules changing the coloration of the skin (increased number of melanosomes). This also causes the different skin tones among humans, but contrasts with lentigines and moles.〔''Robbins and Cotran Pathologic Basis of Disease'' Elsevier. 2005. Page 1232. ISBN 0-8089-2302-1 .〕 == Biology == 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 arms or shoulders. Heavily distributed concentrations of melanin may cause freckles to multiply and cover an entire area of skin, such as the face. 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. Freckles are not a skin disorder, but people with freckles generally have a lower concentration of photo protective melanin, and are therefore more susceptible to the harmful effects of UV radiation. It is suggested that people whose skin tends to freckle should avoid overexposure to sun and use sunscreen. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「freckle」の詳細全文を読む スポンサード リンク
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