While not all basal and squamous cell skin cancers can be prevented, there are ways to reduce your risk of getting skin cancer.

Limit ultraviolet (UV) exposure

The most important way to lower the risk of basal and squamous cell skin cancers is to limit your exposure to ultraviolet (UV) radiation. Practice sun safety when you are outdoors. "Slip! Slop! Slap! … and Wrap" is a catch phrase that reminds people of the 4 key methods they can use to protect themselves from UV radiation. Slip on a shirt, slop on sunscreen, slap on a hat, and wrap on sunglasses to protect the eyes and sensitive skin around them from ultraviolet light.

Protect your skin with clothing

Clothes provide different levels of protection, depending on many factors. Long-sleeved shirts, long pants, or long skirts are the most protective. Dark colors generally provide more protection than light colors. A tightly woven fabric protects better than loosely woven clothing. Dry fabric is generally more protective than wet fabric.

Be aware that covering up doesn't block out all UV rays. A typical light T-shirt worn in the summer usually provides less protection than a sunscreen with a sun protection factor (SPF) of 15 or higher.

A few companies in the United States now make clothing that is lightweight, comfortable, and protects against UV exposure even when wet. Some sun-protective clothes have a label listing the ultraviolet protection factor (UPF) value -- the level of protection the garment provides from the sun's UV rays (on a scale from 15 to 50+). The higher the UPF, the higher the protection from UV rays.

Newer products are also available to increase the UPF value of clothes you already own. Used like laundry detergents, they add a layer of UV protection to your clothes without changing the color or texture.

Wear a hat

A hat with at least a 2- to 3-inch brim all around is ideal because it protects areas often exposed to the sun, such as the neck, ears, eyes, forehead, nose, and scalp. A shade cap (which looks like a baseball cap with about 7 inches of fabric draping down the sides and back) also is good. These are often sold in sports and outdoor supply stores.

A baseball cap can protect the front and top of the head but not the neck or the ears, where skin cancers commonly develop. Straw hats are not recommended unless they are tightly woven.

Use sunscreen

The American Cancer Society recommends using sunscreen as part of a sun protection program.

Use sunscreens and lip balms with an SPF factor of 15 or more on areas of skin exposed to the sun, especially when the sunlight is strong (for example, in hot or high-altitude locations or between the hours of 10 am and 4 pm). Use sunscreen even on hazy days or days with light or broken cloud cover because the UV light still comes through.

Always follow directions when applying sunscreen. For it to work best, sunscreen should be applied about 20 to 30 minutes before you go outside. A 1-ounce application (a palmful of sunscreen) is recommended to cover the arms, legs, neck, and face of the average adult. Protection is greatest when sunscreen is used thickly on all sun-exposed skin. To ensure continued protection, many sunscreens should be reapplied at least every 2 hours. Many sunscreens wash off when you sweat or swim and must be reapplied for maximum effectiveness. And don't forget your lips; lip balm with sunscreen is also available.

Some people use sunscreens in order to stay out in the sun longer without getting sunburned. Sunscreen should not be used to gain extra time in the sun, as you will still end up with damage to your skin.

Sunscreen may reduce your chance of skin cancer, particularly actinic keratoses and squamous cell cancer. But there is no guarantee, and if you stay in the sun a long time, you are at risk of developing skin cancer even if you have applied sunscreen. It is not clear whether sunscreen can help prevent basal cell cancers.

If you want a tan, try using a "sunless" tanning lotion. These can provide the look, without the danger. Sunless tanning lotions contain a substance called dihydroxyacetone (DHA). DHA works by interacting with proteins on the surface of the skin to produce color. You do not have to go out in the sun for these to work. The color tends to wear off after a few days.

Wear sunglasses

Wrap-around sunglasses with at least 99% UV absorption provide the best protection for the eyes and the skin area around the eyes. Look for sunglasses labeled as blocking UVA and UVB light. Labels that say "UV absorption up to 400 nm" or "Meets ANSI UV Requirements" mean the glasses block at least 99% of UV rays. It there is no label, don't assume the sunglasses provide any protection.

Seek shade

Another way to limit exposure to UV light is to avoid being outdoors in sunlight too long. This is particularly important in the middle of the day between the hours of 10 am and 4 pm, when UV light is strongest. If you are unsure about the sun's intensity, take the shadow test: If your shadow is shorter than you, the sun's rays are the strongest. Plan activities out of the sun during these times. If you must be outdoors, protect your skin. Keep in mind that sunlight (and UV rays) can come through clouds, can reflect off water, sand, concrete, and snow, and can reach below the water's surface.

The UV Index: The amount of UV light reaching the ground in any given place depends on a number of factors, including the time of day, time of year, elevation, and cloud cover. To help people better understand the intensity of UV light in their area on a given day, the National Weather Service and the US Environmental Protection Agency have developed the UV Index. It gives people an idea of how strong the UV light is in their area, on a scale from 1 to 11+. A higher number means a higher chance of sunburn, skin damage and ultimately skin cancers of all kinds. Your local UV Index should be available daily in your local newspaper, on TV weather reports, and online (www.epa.gov/sunwise/uvindex.html).

Avoid other sources of UV light

The use of tanning beds and sun lamps is hazardous because the UV radiation they deliver can be damaging to the skin. There is growing evidence that they may increase your risk of developing basal cell and squamous cell skin cancer, as well as melanoma. Researchers are finding that the rate of skin cancer in young people is increasing. One factor may be the use of indoor tanning facilities. Most skin doctors highly recommend not using tanning beds and sun lamps.

Protect children from the sun

Children require special attention, since they tend to spend more time outdoors and can burn more easily. Parents and other caregivers should protect children from excess sun exposure by using the measures described above. Older children need to be cautioned about sun exposure as they become more independent. It is important, particularly in parts of the world where it is sunnier, to cover your children as fully as is reasonable. You should develop the habit of using sunscreen on exposed skin for yourself and your children whenever you go outdoors and may be exposed to large amounts of sunlight.

A word about sun exposure and vitamin D

Doctors are learning that vitamin D has many health benefits. It may even help to lower the risk for some cancers. Vitamin D is made naturally by your skin when you are in the sun. How much vitamin D is made depends on many things, including how old you are, how dark your skin is, and how intensely the sun shines where you live. At this time, doctors aren't sure what the optimal level of vitamin D is, or how best to balance the possible benefits of getting vitamin D from sunlight versus the possible risks of skin cancer. This is an area of very active research. If you have darker skin or live in an area with little daily sunlight, many experts at this time recommend taking vitamin D by mouth, such as in supplements or certain foods. For example, most milk has vitamin D added.

For more information on how to protect yourself and your family from UV exposure, see the American Cancer Society Document, Skin Cancer Prevention and Early Detection.

Avoid harmful chemicals

Exposure to certain chemicals, such as arsenic, can increase a person's risk of skin cancer. People can be exposed to arsenic from well water in some areas, pesticides and herbicides, some medicines (such as arsenic trioxide) and herbal remedies (arsenic has been found in some traditional herbal remedies imported from China), and in certain occupations (such as mining and smelting). High exposure to arsenic should be avoided.

Learn more about skin cancer prevention

Many organizations conduct skin cancer prevention activities in schools and recreational areas. Others develop brochures and public service announcements. For more information, refer to the "Additional resources" section.