One of your skin's worst enemies is ultraviolet light from the sun, which can damage the skin and lead to skin cancer.

What things are most likely to cause skin cancer?

Things that may cause skin cancer include:

• Repeated exposure to bright sunlight, especially when the sun reflects off snow or water.

• Sunburn, especially blistering sunburns during childhood.

• Skin creams or lotions that contain tar, especially if used over a long period of time (these creams are medicines used to treat certain skin problems, such as psoriasis).

• Exposure to organic arsenic, which may be in pesticides and other chemicals.

• Radiation therapy or chemotherapy for cancer.

Risk factors for skin cancer include:

• If any of your close relatives have had malignant melanoma or pre-malignant skin spots, you may have a higher risk for developing skin cancer.

• If you have freckles or fair skin that doesn't tan easily, you may be at risk.

What can I do to reduce my risk of skin cancer?

• Limit your time in bright sunlight.

• Take advantage of whatever shade is available when you're outside.

• Wear cool clothing that covers as much of your body as possible when you're outside. Apply protective sunblock with a skin protection factor (SPF) of at least 15 to the parts of your skin that can't be covered by clothes. This is very important if you're going to be near the water or snow.

• Wear sunglasses to protect your eyes and eyelids.

• Wear lipstick or balm with sunblock to protect your lips.

• If your skin is starting to redden from too much sun, go indoors as soon as possible.

• Don't use tanning booths.

• Talk to your doctor about the risks and benefits of using any skin lotions that contain tar.

• Avoid exposure to chemicals that contain organic arsenic, such as pesticides and herbicides (poison to kill bugs and weeds). Not all of these poisons contain arsenic, but some do.

How often should I check my skin?

Most skin cancers grow slowly. By finding them early and having them removed, you may lessen the chances of the cancer spreading to other parts of your body or scarring your body. You should check your entire body, including your lips and eyelids, at least every six months. You may need some help checking your scalp, your back and the backs of your thighs. If one of your close family members has had skin cancer, or if you have freckles or very fair skin, you should ask your doctor to check your skin every year.

When you check your skin, look for the following:

• Any rough or red, bumpy area on your skin that's bigger than the head of a match and doesn't clear up

• Any area of skin that stays irritated or inflamed (red and itchy)

• Any ulcer (sore) that doesn't heal in two weeks

• Any area that keeps cracking or bleeding

• Any colored spot that's getting bigger

• Any brown or black spot that's wider than 1/4 inch (the size of a pencil eraser) or is changing color or size

Although most skin cancer is not dark, dark spots must be watched very carefully because they may become malignant. Dark moles can change and become more dangerous. Watch dark moles for any of the following signs:

• Growing to more than 1/4 inch across

• Becoming asymmetrical (uneven) in shape

• Developing an irregular edge

• Developing an uneven color

• Developing a raised area

If you're concerned about anything you find on your skin, visit your doctor right away. Your doctor will tell you if it's harmless. If not, your doctor can remove it and have it checked for cancer.