Skin cancer is the most common type of cancer in the United States. According to current estimates, 40 to 50 percent of Americans who live to age 65 will have skin cancer at least once. Although anyone can get skin cancer, the risk is greatest for people who have fair skin that freckles easily.

UV radiation from the sun is the main cause of skin cancer. In addition, artificial sources of UV radiation — such as sunlamps and tanning booths — can cause skin cancer. People who live in areas of the U.S. that get high levels of UV radiation from the sun are more likely to get skin cancer. For example, skin cancer is more common in Texas and Florida than in Minnesota, where the sun is not as strong.

There are three common types of skin cancers. Basal cell carcinomas are the most common, accounting for more than 90 percent of all skin cancers in the United States. They are slow-growing cancers that seldom spread to other parts of the body. Squamous cell carcinomas also rarely spread, but they do so more often than basal cell carcinomas. The most dangerous of all cancers that occur in the skin is melanoma. Melanoma can spread to other organs, and when it does, it often is fatal.

Both basal and squamous cell cancers are found mainly on areas of the skin exposed to the sun — the head, face, neck, hands, and arms. However, skin cancer can occur anywhere. Changes in the skin are not sure signs of cancer; however, it’s important to see a doctor if any symptom lasts longer than 2 weeks. Don’t wait for the area to hurt — skin cancers seldom cause pain.

All skin cancers could be cured if they were discovered and brought to a doctor’s attention before they had a chance to spread. Therefore, you should check your skin regularly. The most common warning sign of skin cancer is a change on the skin, especially a new growth or a sore that doesn’t heal. Skin cancers don’t all look the same. For example, skin cancer can start as a small, smooth, shiny, pale, or waxy lump. Or it can appear as a firm red lump. Sometimes, the lump bleeds or develops a crust. Skin cancer also can start as a flat, red spot that is rough, dry, or scaly.

In treating skin cancer, the doctor’s main goal is to remove or destroy cancer completely, leaving as small scar as possible. To plan the best treatment for each person, the doctor considers the type of skin cancer, its location and size, and the person’s general health and medical history. Treatment for skin cancer usually involves some type of surgery. In some cases, radiation therapy or chemotherapy (anticancer drugs) or a combination of these treatments may be necessary.

Age spots, or “liver spots” as they’re often called, have nothing to do with the liver. Rather, these flat, brown spots are caused by years of sun exposure. They are bigger than freckles and appear in fair-skinned people on sun-exposed areas such as the face, hands, arms, back, and feet. The medical name for them is solar lentigo. They may be accompanied by wrinkling, dryness, thinning of the skin, and rough spots.

A number of treatments are available, including skin-lightening, or “fade” creams; cryotherapy (freezing); and laser therapy. Tretinoin cream is approved for reducing the appearance of darkened spots. A sunscreen or sun block should be used to prevent further damage.

Many older people notice an increased number of bruises, especially on their arms and legs. The skin becomes thinner with age and sun damage. Loss of fat and connective tissue weakens the support around blood vessels, making them more susceptible to injury. The skin bruises and tears more easily and takes longer to heal.

Sometimes bruising is caused by medications or illness. If bruising occurs in areas always covered by clothing, see a doctor.

The best way to keep your skin healthy is to avoid sun exposure.

Stay out of the sun. Avoid the sun between 10 a.m. and 3 p.m. This is when the sun’s UV rays are strongest. Don’t be fooled by cloudy skies. Harmful rays pass through clouds. UV radiation also can pass through water, so don’t assume you’re safe if you’re in the water and feeling cool.

Use sunscreen. Sunscreens are rated in strength according to a sun protection factor (SPF), which ranges from 2 to 30 or higher. A higher number means longer protection. Buy products with an SPF number of 15 or higher. Also look for products whose label says: broad spectrum (meaning they protect against both types of harmful sun rays — UVA and UVB) and water resistant (meaning they stay on your skin longer, even if you get wet or sweat a lot). Remember to reapply the lotion as needed.

Wear protective clothing. A hat with a wide brim shades your neck, ears, eyes, and head. Look for sunglasses with a label saying the glasses block 99 to 100 percent of the sun’s rays. Wear loose, lightweight, long-sleeved shirts and long pants or long skirts when in the sun.

Avoid artificial tanning. Don’t use sunlamps and tanning beds, as well as tanning pills and tanning makeup. Tanning pills have a color additive that turns your skin orange after you take them. The FDA has approved this color additive for coloring foods but not for tanning the skin. The large amount of color additive in tanning pills may be harmful. Tanning make-up products are not suntan lotions and will not protect your skin from the sun.

Check your skin often. Look for changes in the size, shape, color, or feel of birthmarks, moles, and spots. If you find any changes that worry you, see a doctor. The American Academy of Dermatology suggests that older, fair-skinned people have a yearly skin check by a doctor as part of a regular physical exam.