How do freckles develop?
Freckles are caused by uneven distribution of skin pigment melanin in the skin. Freckles become more prominent when exposed to sunlight because the skin produces extra melanin in sunny conditions. The sun and sun-tanning lights emit ultraviolet (UV) rays. After exposure to sunlight, the outer layer of the skin (the epidermis) thickens and the pigment-producing cells (the melanocytes) in the skin produce the pigment melanin at an increased rate. After exposure to sunlight,
the outer layer of the skin thickens and the pigment-producing cells in the skin produce melanin at an increased rate. (This gives some protection against future sun exposure.)
People differ of course a great deal in their reaction to sunlight. To take an extreme example, there is no pigmentation in the skin of an albino because of a defect in melanin metabolism. On the other hand, people with dark complexions are relatively less sensitive to sun exposure than fair-skinned persons. However, persons with dark skin are not entirely resistant to the effects of the sun and they, too, can become sunburned with prolonged exposure. Persons with blonde or red hair are especially susceptible since they tend to be the fairest skinned. Irrespective of skin color, it is the uneven distribution of the melanin pigment in the skin that results in freckling. A freckle is nothing more than an unusually heavy deposit of melanin at one spot in the skin.
Freckles, age spots and pregnancy mask have several things in common. They are formed in sun exposed areas: face, hands, chest and back. These unwelcome brown patches are nothing more than accumulation of skin pigment melanin which is always produced by the skin. The amount of melanin present determines the skin tone of an individual. Extra melanin is produced by the body in response to sun exposure. It absorbs UV rays and does not allow them to penetrate deep into the skin layers as it would be damaging.