DEAR DR. DONOHUE: Recently, my daughter attended a sweet-16 birthday party for one of her best friends. She is a beautiful girl. When my daughter showed me pictures of her friend, I was shocked. Her face and arms were deeply tanned. I have no idea how many hours she must have spent under a tanning machine. I am very concerned about her. Would you write about the dangers of tanning? — Anon.

ANSWER: Ultraviolet light, the kind of light we don’t see, has powerful effects on the skin. Ultraviolet A rays constitute 95 percent of the UV light that makes its way to earth. UV A rays do not burn and tan skin as much as UV B rays, but they do damage skin. They cause skin wrinkling; they dry skin; and they produce age spots (liver spots). And they also add to the risk of skin cancer.

Ultraviolet B rays are more destructive. They are the burning rays, and they have a greater effect on skin cancer production. Both A and B reduce the skin’s innate immunity.

Exposure to both UV A and UV B injures the skin cells’ DNA, and that’s what sets the scene for future skin cancer. Humans have learned to cope with UV light by tanning. A tan offers some protection against further damage. UV light activates melanocytes, and they pass their melanin – a dark pigment — to other skin cells. That has the effect of providing an umbrella for the skin. However beneficial that might be, the fact remains that in obtaining a modicum of protection with a tan, skin-cell DNA has been dealt a major blow. No tan can be considered healthy. Sun exposure in adolescence might be the most dangerous time for ultraviolet damage.

Tanning booths and tanning beds are considered a threat equal to the sun for promoting future skin cancer.

People of all ages should protect their skin from exposure to UV light. Such exposure happens every time a person goes outdoors. Cloud cover is a poor absorber of UV rays and offers little skin protection. Sunscreen application should become a habit.

DEAR DR. DONOHUE: I took simvastatin for a year and a half. This fall, I started encountering severe muscle discomfort and weakness in my upper body. I discontinued the drug and haven’t taken it for two months. My doctor ordered blood tests, and they all came back negative.

Should the pain and discomfort be gone by now if the statin was the cause? What field should a specialist be in to advise me? I have run for years, and I did extensive hiking. — S.N.

ANSWER: If your blood tests show no muscle involvement (a rise in muscle enzymes), then it’s difficult to pin the muscle pain on the statin drug, especially after a two-month hiatus.

If your primary-care doctor is stumped, see a rheumatologist, a neurologist or an orthopedic surgeon. All three are skilled in muscle illnesses.

DEAR DR. DONOHUE: I am sick and tired about all this exercise talk. What proof exists that it is such a health boon? I am not into exercise, have never been into it and probably will never be into it. Can you say with a straight face that proof really exists that exercise extends life? — R.R

ANSWER: Yes, I can. And I can do so with a straight face.

The studies that show exercise improves health are too numerous to cite. A recent study showed that men (although no women were included in the study, I am sure it applies equally to them) who increased the intensity and frequency of physical exercise had their mortality cut in half from a control group that did not exercise. Consistent exercise bestows the same health benefits that come from not smoking.

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.