The exact cause of<unk>  is unknown.<unk>  is thought to be the stimulation of melanocytes (cells in the dermal layer, which transfer the pigment melanin to the keratinocytes of skin) when the skin is exposed to ultraviolet light from the sun. Small amounts of sun exposure can make<unk>  return to the skin after it has faded, which is why people with<unk>  often get it again and again, particularly in the summer. Pregnant women often get<unk> , or chloasma, known as the mask of pregnancy. Birth-control pills and hormone replacement therapy also can trigger<unk> . The discoloration usually disappears spontaneously over a period of several months after giving birth or stopping the oral contraceptives or hormone treatment. Genetic predisposition is also a major factor in determining whether someone will develop<unk> . People with the Fitzpatrick skin type III or greater from African, Asian, or Hispanic descent are at a much higher risk than others. In addition, women with a light brown skin type who are living in regions with intense sun exposure are particularly susceptible to developing this condition. The incidence of<unk>  also increases in patients with thyroid disease. It is thought that the overproduction of melanocyte-stimulating hormone brought on by stress can cause outbreaks of this condition. Other rare causes of<unk>  include allergic reaction to medications and cosmetics. Addison's disease<unk>  suprarenale (Latin - above the kidneys) is a symptom of Addison's disease, particularly when caused by pressure or minor injury to the skin, as discovered by Dr. FJJ Schmidt of Rotterdam in 1859.
Melasma
Tar melanosis
Xanthelasma
Ichthyosis
Pomade acne
Feline acne
Melanosis
Erythrasma