Skin Pigmentation

Skin is an amazing organ. It covers the whole body and is capable of regeneration. The average adult has 8 pounds (3.6 kilograms) and 22 square feet (2 square meters) of skin [source: National Geographic]. In addition to its aesthetic role, skin functions as a temperature regulator, a shield against bacteria and water loss, a storage center for water and fat, and it allows us to feel the world around us.

While you may use the terms "thick-skinned" and "thin-skinned" to refer to a person's temperament, it's also true that we all have varying depths of skin on different parts of our bodies. The eyelids are the thinnest skin we possess, and because of their respective functions, the soles of the feet and the palms of the hands are thick.

Skin pigmentation resides in the epidermis, or the thin outer segment of the three layers that make up the skin. The epidermis alone is made up of three tiny sub-layers. Pigment does not reach the dermis, the middle layer of skin [source: University of Maryland Medical Center].

You get tan when your epidermis reacts to the ultraviolet (UV) rays of the sun. Your melanocytes get a message from your skin that says, "Hey, potential damage here. Protect me!" Melanocytes then produce more melanin, which protects skin from sun damage. Unfortunately, the body's natural protection is not enough to completely prevent damage and disease caused by the strong rays of the sun.

Continue to the next page to learn about things that can go wrong with your skin pigmentation.

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.

Although skin color is often categorized as black, red, yellow or white, nobody's skin is truly any of these colors. Our skin color lies somewhere on a continuum of shades from very dark brown to almost pink. Skin color changes throughout our lives because of sun exposure and other factors.

Researchers believe a clear correlation exists between where your ancestors lived and skin color. In sunnier, hotter climates, darker skin is more advantageous because it protects the body from UV rays. As people migrated to colder, less sunny environments, dark skin prevented enough vitamin D production, which in turn led to rickets and death. Lighter-skinned people were able to produce more vitamin D and live on to reproduce [source: Dreifus]. Darker-skinned people who now live in colder climates are still susceptible to rickets and, some scientists believe, other diseases because they are not getting enough vitamin D.

Deliberate sun exposure may lead to that evenly bronzed look common in celebrities, but it can also lead to a spray of freckles across the bridge of your nose or all over your face. It's no coincidence that redheads, typically bearers of the fairest skin of them all, are prone to freckles since their skin is very sensitive to the sun's rays.

Many people bask in the sunshine not to get vitamin D, but to get a tan. To read about the potential downsides of that so-called healthy glow, move on to the next page.

It's common knowledge that too much sun exposure is not a good thing. No one wants to end up with leathery, snake-like skin. But that's only one side effect of letting UV rays attack your body.

The three most common forms of skin cancer can be traced to sun damage, and all three are on the rise. Basal cell carcinoma is the most common nonmelanoma skin cancer and the most treatable form, but if it's left untreated too long, it can cause damage to nearby tissue and bone. Basal cell is also the most likely skin cancer to recur. Squamous cell carcinoma is second most common form of nonmelanoma skin cancer, and it is completely curable when caught and treated. Melanoma, the most dangerous of the skin cancers, affects the melanocytes. It, too, is curable when caught early, but can be deadly when left untreated [source: Mayo Clinic].

Other skin pigmentation conditions are more cosmetic in nature. Age spots, also known as solar lentigos, can be traced directly to sun exposure. While they are not dangerous in themselves, age spots can indicate a risk of skin cancer. Rough, scaly, discolored patches of skin that don't go away may be actinic keratoses, or solar keratoses. As the name implies, they also arise from exposure to too much sun. Sometimes, these patches can evolve into squamous cell carcinoma.

Skin pigmentation may be an adaptation to a past migration, but in a way, humans must continue to adapt -- this time by making sure we take in only the appropriate amount of sunlight, regardless of our skin color.

For more information about sun exposure and your skin, read on to the following page.