DEAR DR. DONOHUE: I am the mother of six children. The oldest is a boy, 18, and the youngest a girl, 6. All my children spend their free time outdoors. The boy is a lifeguard at an outdoor pool. Two of my daughters play baseball and practice all the time. The rest are outside, too. These kids are exposed to sunlight just about every day. Are they going to come down with skin cancer? — R.C.

ANSWER: The sun has powerful effects on the skin, both good and bad. Sunlight turns a substance found in the skin into a precursor of vitamin D. With a couple of alterations by the liver and kidneys, the final vitamin is produced. Vitamin D keeps bones strong. It has a multitude of other important jobs, which only recently have been discovered. Sunlight provides most of our vitamin D. We don’t need a lot of sun, only five to 15 minutes of it on the arms and legs, three times a week.

On the downside, the sun’s ultraviolet rays can lead to skin cancers. Your children are not bound to develop skin cancer, but constant exposure to ultraviolet rays increases their risk. UV rays also age the skin. Old skin’s wrinkles are due more to sunlight than they are to aging.

Ultraviolet B rays are the ones involved in burning the skin, and they have the most influence on the development of skin cancer. Ultraviolet A rays, 95 percent of the UV radiation, penetrate deeply into the skin and have a hand, but a lesser one, in producing cancer.

Your kids can have their sunlight without danger if they use sunscreen. Sunscreen should have an SPF (sun protection factor) between 15 and 30. The best protection is sunscreen that blocks both UVA and UVB. It should be applied 15 to 30 minutes before going outside, and it should be reapplied every two hours. If the children swim or sweat heavily, it should be reapplied after they leave the water or after they have dried themselves of sweat.

I am aware that there are some who maintain that sunscreens promote skin cancer. Until the U.S. Food and Drug Administration, the Canadian Academy for Occupational Health and Safety and the American Academy of Dermatology say that is true, I continue to use them.

TO READERS: The booklet on fitness gives instructions on how to start an exercise program. To obtain a copy, write: Dr. Donohue — No. 1301, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I have sprained both my ankles many times. I’m not a super athlete. It happens when I am walking. My ankle turns to one side. It happens more often when I run. How can I strengthen my ankles? — L.L.

ANSWER: The ankle doesn’t have any muscles. Tendons from the lower leg muscles provide support to it. Ligaments, bands of strong tissue, also keep the ankle firmly aligned. A sprain is a stretching or actual tearing of those ligaments. Some people are born with flimsy ligaments. And some people don’t have a good sense of balance. Those people often sprain their ankles.

Sitting on a chair with one leg out in front, trace the letters of the alphabet with your foot. Then switch legs. Another exercise is to walk alongside a wall. You can use the wall for support if you start to wobble. Walk about 10 steps forward on your toes. Turn around and walk 10 steps back on your heels.

DEAR DR. DONOHUE: I have some suggestions for the person who was getting blisters while walking. There is an anti-chafe product called Body Glide. It looks like stick deodorant. You can apply it to any body part that rubs against another or against the shoe. You can use it anywhere on your feet where blisters form. — T.P.

ANSWER: Thanks for the tip. I haven’t used it, and I don’t know how easy it is to find. I am going to look for it and try it out.

I will include your other tips at a later time.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.