Things can go awry with almost any aspect of the human body, but when something happens to your skin, it can be very noticeable. On the bright side, the cosmetic change people see is often the worst symptom of skin pigmentation problems.
Skin pigmentation disorders may make your skin either darker or lighter. Lightening is called hypopigmentation and darkening is called hyperpigmentation. Simply having a light or dark patch does not automatically signal a problem, but it can.
White bunnies that have pink eyes, known as albinos, technically have a pigmentation disorder. Albinos do not have any melanin and, therefore, do not have any pigment in their skin, eyes or hair. Humans who are albinos have very light skin because of the lack of melanin. They may also have very light hair and light eyes. Albinism is an inherited condition [source: Cleveland Clinic]. Vitiligo is another hypopigmentation disorder. With this condition, the body destroys its melanocytes or they fail to function properly, so a person cannot produce melanin, and their skin loses its color. This does not happen overnight, nor does it happen evenly throughout the body [source: American Vitiligo Research Foundation].
A hyperpigmentation condition called melasma (black spot) is sometimes referred to as "the mask of pregnancy," because it commonly appears on the faces of pregnant women. In that case, it's the hormone imbalances that coincide with pregnancy which cause the condition. Women who are going through menopause or using hormone-based birth control methods may also notice patches of their skin -- especially skin that is exposed to the sun -- becoming darker. Melasma may go away on its own, but it can also be treated with prescription creams or over-the-counter skin care products if it persists.
You may have also seen older people who have darkened bands of skin around their necks or on their cheeks. The medical name for this condition is poikiloderma of Civatte, but most people just call it sun aging -- which is appropriate because it is caused by staying in the sun too much. Most of the time, it does not cause any discomfort.
With any of these pigmentation-affecting conditions, using sunscreen and limiting sun exposure is very important to prevent further damage.
Many scientists believe skin color is a reflection of how much sun exposure your ancestors got in their native regions. Read on to learn more about this theory and others related to skin color.