DEAR DR. DONOHUE: I am 70 years old (10 in dog years) and in reasonably good health if you overlook arthritis and the other problems that befall us oldies but goodies. My most serious problem is what I have determined to be, but not had diagnosed, bursitis in my left shoulder. It feels like a 6-inch knife is sticking in it. I have tried several sports creams for relief, but none has helped. My doctor has prescribed hydrocodone. All that did for me is make me feel stupid with a sore shoulder. Do you have any ideas how to relieve the discomfort? A good friend urges me to use DMSO. He swears by it, but I am a little apprehensive. — D.B.

ANSWER: The shoulder is the body’s most versatile joint. Its versatility makes it vulnerable to many problems. Bursitis is one, but far from the leading one. Bursas are small disks placed between tendons and bones to reduce friction when tendons glide across the bone. With shoulder bursitis, the shoulder develops an achy pain that worsens with overhead movements such as lifting something to a high shelf. The pain might spread to the biceps muscle on the front of the upper arm. Bursitis, no matter where it is, usually responds to rest and anti-inflammatory medicines like Aleve and Advil. Pennsaid is an anti-inflammatory medicine that comes as a liquid for application directly to the painful area. This route spares the stomach from any irritation. Rest doesn’t mean total immobility; if you keep the shoulder motionless, it could freeze.

Why did you pick bursitis as the cause of your pain? A tear of the rotator cuff — a band of tendons that come from the back muscles and cross over the shoulder to keep it in place — is a more common disorder, and a disorder that strikes older people. Its pain is felt in the front and the side of the shoulder, and the pain is at its worst in bed. Impingement syndrome is another common shoulder disorder. It’s due to compression of tendons between bones. Its pain often is described as “throbbing.”

You must get the true diagnosis. If need be, see an orthopedic surgeon. You’re not going to improve without knowing exactly what has gone wrong.

Your friend wants you to use DMSO, dimethyl sulfoxide. It isn’t approved by the Food and Drug Administration for this purpose. I’m leery of using anything that hasn’t won the seal of approval from the FDA.

DEAR DR. DONOHUE: I am 85 and attend exercise classes. I walk every other day and take only one prescription pill.

Last month I discovered a pimple on my left cheek. If it wasn’t for a nurse friend, I probably would have picked it. She advised me to see a dermatologist. It turned out to be a basal cell cancer, which was removed. I asked the doctor how I got it, and he said it was from too much sun. I was a sun goddess in my youth, spending almost every day at the beach. Why did it have to show up on my face? — A.Z.

ANSWER: Basal cell skin cancers are slow-growing cancers that almost never spread to distant places in the body. However, they can bore deeply into tissues beneath the skin and become most disfiguring.

You got it on your face because the face is the body part most exposed to sunlight.

Basal cells vary in their appearance. They can start out as pearly-white or pink dome-shaped growths that do resemble a pimple — somewhat. Frequently they form a scab that heals but returns time and again. Thanks for telling your story. It puts all of us on guard for basal cell cancer.

DEAR DR. DONOHUE: When I was 6 years old in 1927, I was one sick kid. My folks took me to our family doctor, who said, “This lad has pernicious anemia, and I am prescribing for him calf’s liver three or four times a week, along with cod liver oil and lots of fresh air.” That doctor must have known what he was talking about. I am now 90. — W.D.

ANSWER: Liver was treatment for pernicious anemia before vitamin B-12 was available in shot form. Liver has large amounts of it. The cod liver oil is a little puzzling. It has vitamins A and D, but no B-12.

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.