Disorders of the Skin - Pigment disorders and birthmarks
The mechanism that controls skin coloration is described above under “Skin Color.” Abnormalities in the creation and distribution of melanin result in the following disorders, some of which are negligible.
These are small spots of brown pigment that frequently occur when fair-skinned people are exposed to the sun or to ultraviolet light. For those whose skin gets red rather than tan during such exposure, freckles are a protective device. In most cases, they recede in cold weather. A heavy freckle formation that is permanent can be covered somewhat by cosmetic preparations. No attempt should be made to remove freckles with commercial creams or solutions unless supervised by a physician.
Flat, smooth, irregularly placed markings on the skin, called liver spots , often appear among older people, and result from an increase in pigmentation. They have nothing to do with the liver and are completely harmless. Brownish markings of similar appearance sometimes show up during pregnancy or as a result of irritation or infection. They usually disappear when the underlying cause is eliminated.
Liver spots are permanent, and the principal cause is not aging but the accumulated years of exposure to sun and wind. They can be disguised and treated in the same way as freckles. A liver spot that becomes hard and thick should be called to a physician's attention.