May 2003

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Avoid the burn: Prevent skin cancer

By Ruth SoRelle, MPH

John Wolf MD

The best way to prevent skin cancer is to minimize your exposure to the sun – or at least the ultraviolet rays that can damage your body’s largest and most protective organ.

“The message we are trying to get across is that sunlight is the principal provocateur for skin cancer,” said John Wolf, MD, chair of the department of dermatology at Baylor College of Medicine. Long periods of exposure to the sun are the major causes of common skin cancers such as basal cell and squamous cell carcinoma.

Avoid that bad blistering sunburn

Melanoma, the more dangerous form of skin cancer, is associated with long periods of sun exposure as well as bad sunburns in childhood.

“Three or more blistering sunburns in childhood are an independent risk factor for melanoma,” said Wolf. “We know that sunlight damage plays a major role in the evolution of all forms of skin cancer.

“One of the best pieces of advice to give anyone is to minimize sunlight damage,” he said. “Many people misunderstand what that means.”

Plan major outdoor activities for the early morning and the late afternoon. Avoid sun exposure from 10 a.m. until at least 2 p.m. and until 5 p.m. in sunny settings. Wear protective clothing – long sleeves, long pants and a hat that covers your head, not just the front. Eat a low-fat diet. Use a broad-spectrum sunscreen that protects against both the A and B forms of ultraviolet light. Every month or so, examine your skin using a full-length mirror. Use a hand mirror to see in back of your body or ask someone else to check the skin on the back of your body. Look for moles that are very black, have variations in color or are very irregular. Look for pale, pearly nodules or scaly red irregular patches. If you see something that raises a concern, consult a dermatologist.
Keep them out of the sun during the hottest parts of the day. Teach them to wear protective clothing. Put the sunscreen on them every day and renew it regularly. If you start this early, it will become a routine they follow in the future. Do your best to prevent them from becoming sunburned.

How and when you get sun damage

Estimates are that 70 percent of sunlight damage is caused by exposure during everyday activities – from going out to get the paper in the morning to carrying groceries into the house in the late afternoon.

“You are getting a tremendous amount of sunlight exposure, whether you know it or not,” said Wolf. “You don’t have to be sailing or lying on the beach. That means you should be careful about it every day.”

For example, Wolf plans to swim regularly during the summer. He will limit his swimming to early morning or after he gets home in the late afternoon or early evening.

Protective clothes

Protective clothing can also provide a barrier against the sun’s damaging rays. Protective clothes include long-sleeved shirts, pants and a hat, which is particularly important for men who are loosing their hair on top. The hat should protect the top of the head, ears, face and back of the neck.

“Many people make the mistake of just wearing a baseball cap,” said Wolf. “That just protects the front of the head and scalp.”

If the cap is made of mesh for the sake of coolness, it may not even protect the scalp. The rays of the sun can penetrate the loose weave of the fabric.

“Most people assume that clothing is totally protective and that is not true,” said Wolf. The protection given by ordinary clothing is incomplete. Often people wear T-shirts for swimming, assuming that they are protected from the sun. A wet T-shirt has only a minimal sun protection factor. Some manufacturers produce clothing with a tighter weave that has greater sunlight protection, he said.

All of these measures provide some protection, but no matter how carefully you plan, it is impossible to completely avoid exposure to sunlight, said Wolf.

Sunscreens

That is why sunscreens and sun blocks are a must, he said.

“Technically, a sun block, like zinc oxide, truly blocks the sun’s rays. Sunscreen would be something that partially blocks the sun by a chemical or physical effect.”

“Many of today’s sunscreens have tiny particles of blocking agents such as titanium oxide dispersed throughout the lotion or cream. These block the rays of the sun. One nice feature is that they don’t have a chemical sunscreen and are less likely to irritate the skin. Some of the early sunscreen would cause irritation and allergies. Many of them sting when they are combined with sweat,” Wolf said.

Today, most sunscreens block against the types of ultraviolet radiation most commonly seen in the atmosphere – UVA and UVB. They are considered broad-spectrum.

“UVA is long-range ultraviolet light in the tanning part of the spectrum. UVB is shorter-range, but it is most often associated with sunburn,” said Wolf. When a person goes to a tanning parlor, he or she is exposed mostly to UVA, although it is impossible to keep all UVB out. A new treatment for psoriasis called PUVA (psoralen and ultraviolet radiation) also uses UVA.

The SPF factor

Dermatologists usually recommend a broad-spectrum sunscreen with a sun protection factor (SPF) of at least 15 for every day use. If a person intends to stay out in the sun longer or has skin that is very sensitive to the sun, he or she should use a sunscreen with an SPF of 30 or even higher, said Wolf. Diuretics, antibiotics and other medications can also increase sensitivity to the sun, requiring a sunscreen with a higher SPF factor, he said.

If you use a sunscreen with an SPF of 15, you are getting between 90 and 95 percent of the protection such compounds can provide. Going with an SPF of 30 will increase protection, but it will not double it, said Wolf.

“If you are going to be physically active or going swimming, then you should reapply the sunscreen during that activity,” he said. No sunscreen is truly waterproof.

Use a large amount of sunscreen. Apply the sunscreen at least half an hour before going outside to give it time to bind to the stratum corneum – the dead and dying cells filled with mature keratin, the primary material that makes up skin, hair and nails. If you are planning to swim in a T-shirt, put the sunscreen on under the T-shirt, which has an SPF of only 2 to 3.

The use of sunscreens has become controversial lately, said Wolf. Some experts are concerned that people will extend their stays in the sun because they are convinced that the sunscreen will protect them.

“If you were ordinarily going to spend two hours in the sun and you use a sunscreen before going out for your two hours, the sunscreen will help you,” he said. If you ordinarily spend two hours in the sun, but when you use sunscreen, you end up spending six hours in the sun, you could end up with damage you might not have had.

Eating low fat

An unexpected way of lowering your risk of skin cancer is to eat a low-fat diet, said Wolf. In 1994, he and other members of his department published the results of a federally sponsored study that evaluated the effect of a low-fat diet on the occurrence of precancerous skin lesions called actinic keratoses.

The researchers randomly assigned 76 patients to eat their usual diet (approximately 40 percent fat) or a diet that was 20 percent fat. During the two-year study, physicians who did not know which diet the patients were following examined the patients for new actinic keratoses.

In months 4 through 24, there was an average of three new actinic keratoses per patient in the group on the low-fat diet and 10 in the group on the high-fat diet. (New Engl J Med 330:1272-1275 May 5, 1994)

The study is important, he said, because it does not look back at what happened but instead followed people who were instructed in how to change their diet and whose dietary changes were monitored.

Preventing skin cancer can also depend on genetics and exposure to chemicals as well as sunlight. Seventy percent of damage from sunlight occurs before a person is 17, he said.

It’s never too late

“It is important to protect your children,” he said.

But, adults are not totally lost, he said. Most of them have skin that has passed the first or initiation phase of skin change because it has been sun-damaged. In this phase, the sun has actually damaged the DNA in the skin and the cells have the potential to become a cancer. However, by avoiding a second “hit” from sun damage, they can avoid the promotion and progression stage that results in skin cancer.

“That means it is never too late if something works,” he said.

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