Freckles, sometimes called ephelides (singular ephelis), are clusters of concentrated melaninized cells which are most easily visible to people with a fair complexion. Freckles do not have an increased number of the melanin-producing cells, melanocytes, but instead have melanocytes that overproduce melanin granules (melanosomes) changing the coloration of the outer skin cells called (keratinocytes). As such, freckles are different from antigens and moles
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 in infants, and more commonly found in 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.