Skin cancer — the abnormal growth of skin cells — most often develops on skin exposed to the sun. But this common form of cancer also can occur on areas of the skin not ordinarily exposed to sunlight.

What is it?

There are three major types of skin cancer: basal cell carcinoma, squamous cell carcinoma and melanoma. Basal and squamous cell carcinomas are slow growing and highly treatable, especially if found early. Melanoma is the most serious form of skin cancer. It affects deeper layers of the skin and has the greatest potential to spread to other tissues in the body.

All three types of skin cancer are on the rise — but most skin cancers can be prevented by limiting or avoiding exposure to ultraviolet (UV) radiation and by paying attention to suspicious changes in your skin. If caught early enough, most skin cancers can be successfully treated.

What causes it?

Your skin consists of three layers — the epidermis, dermis and subcutis. The epidermis, the topmost layer, is as thin as a pencil line. It provides a protective layer of skin cells that your body continually sheds. Squamous cells lie just below the outer surface. Basal cells, which produce new skin cells, are at the bottom of the epidermis. The epidermis also contains cells called melanocytes, which produce melanin — the pigment that gives skin its normal color. When you're in the sun, these cells produce more melanin, which helps protect the deeper layers of skin. The extra melanin is what produces the darker color of tanned skin.

Normally, skin cells within the epidermis develop in a controlled and orderly way. In general, healthy new cells push older cells toward the skin's surface, where they die and eventually are sloughed off. This process is controlled by DNA — the genetic material that contains the instructions for every chemical process in your body. But when DNA is damaged, changes occur in these instructions. One result is that new cells may begin to grow out of control and eventually form a mass of cancer cells.

The role of UV light

Much of the damage to DNA in skin cells results from ultraviolet (UV) radiation found in sunlight and in commercial tanning lamps and tanning beds. UV light is divided into three wavelength bands: ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC). Only UVA and UVB rays reach the earth. UVC radiation is completely absorbed by atmospheric ozone.

At one time scientists believed that only UVB rays played a role in the formation of skin cancer. And UVB light does cause harmful changes in skin cell DNA, including the development of oncogenes — a type of gene that can turn a normal cell into a malignant one. UVB rays are responsible for sunburn and for many basal cell and squamous cell cancers. But UVA also contributes to skin cancer. It penetrates the skin more deeply than UVB does, weakens the skin's immune system and increases the risk of cancer, especially melanoma.

Tanning beds deliver high doses of UVA, which makes them especially dangerous. What's more, occasional exposure to intense UVA puts you at greater risk of skin cancer than spending long hours in the sun does. An initial high dose of UV radiation will severely damage melanocytes, but not destroy them. When these damaged cells are subjected to further intense bouts of UVA light, they have little capacity to repair their DNA. This makes them more likely to become malignant.

Other factors

Sun exposure doesn't explain melanomas or other skin cancers that develop on skin not ordinarily exposed to sunlight. Heredity may play a role. Skin cancer can also develop from exposure to toxic chemicals.

What are the symptoms?

Skin cancer can look many different ways. The most common sign of skin cancer is a change on the skin, such as a growth or a sore that won't heal. Sometimes there may be a small lump. This lump can be smooth, shiny and waxy looking, or it can be red or reddish brown. Skin cancer may also appear as a flat red spot that is rough or scaly. Not all changes in your skin are cancer, but you should see your doctor if you notice changes in your skin. Melanoma can form from or near a mole, so it is important to have your health care provider check unusual (atypical) moles that are larger than others, have different colors, or that have irregular edges (borders). The American Academy of Dermatology says that if you notice a mole on your skin, look for the simple "ABCD" warning signs of melanoma:

• Asymmetry - one half does not match the other half.
• Border irregularity - the edges are ragged, notched or blurred.
• Color - the pigmentation is not uniform. Shades of tan, brown or black are present, causing a mottled, or splotchy, appearance. Dashes of red, white, and blue add to the mottled appearance.
• Diameter - the width is greater than six millimeters (about the size of a pencil eraser). Any growth of a mole should be of concern.

Malignant melanoma usually begins as a mottled, light brown to black flat blemish with irregular edges and is at least one-quarter inch in size. It can turn red, blue or white, or bleed and crust on the surface.

Are there any natural therapies?

• Antioxidant nutrients such as vitamin A (betacarotene), vitamin C, and vitamin E can help reduce the risk of cell damage, especially when taken in conjunction with the minerals zinc and selenium
• Essential fatty acids, such as those found in Evening Primrose and Fish Oils, are also essential for the health of the skin.

What else can I do?

The best cure is prevention. Most skin cancers are preventable. To protect yourself:

• Avoid the sun between 10 am and 4 pm - the sun's rays are strongest during this period.
• Wear sunscreen year-round - sunscreen's don't filter out all harmful UV radiation, especiall the radiation that can lead to melanoma.
• Wear protective clothing - suncreen does not provide total protection from the UV rays. That's why it's a good idea to also wear dark, tightly woven clothingthat covers as much skin as possible.
• Avoid tanning beds and tan-accelerating agents.
• Be aware of sun-sensitizing medications.
• Check you skin regularly for changes.
• Have regular skin exams.
  

Did you know?

Treatment for skin cancer and the precancerous skin lesions known as actinic keratoses varies, depending on the size, type, depth and location of the lesions. Often the abnormal cells are surgically removed or destroyed with topical medications. Most treatments require only a local anesthetic and can be done in an outpatient setting. Sometimes no treatment is necessary beyond an initial biopsy that removes the entire growth.

A consumer advocacy group has a warning for parents who think they‘re protecting their family with sunscreen: You may be getting burned.

A study carried out by the Sunscreen Guide by Environmental Working Group (EWG), a Washington-based non-profit organisation, concluded that only 8% out of the 500 sunscreen products they looked at were any good.

See how your sunscreen stacks up...