DEAR DR. DONOHUE: I am plagued with cold sores, especially after being exposed to the sun. Why? Is there anything I can do to prevent this? I understand that cold sores are the byproduct of the herpes virus, and a person carries the virus for life. I use a product called l-lysine, and it dries them. I am leery of it because it might not be a regulated medicine. How does it work? – M.L.

By the age of 25, 50 percent of the population, both here and throughout the world, is infected with herpes-1 virus. By age 70, 90 percent is infected.

Once infected, a person stays infected for life. The virus takes up permanent residence in nerve cells, and it is impossible to evict it. It hibernates. Occasionally, it wakes from sleep, lumbers down the nerve roots to the skin and bursts forth as a cold sore (“fever blister” is another name).

Ultraviolet light definitely wakens the virus. Don’t go out in the sun without protecting your lips and face with sunscreen that has an SPF of 15 or higher. I don’t know what it is about sunlight that activates the virus. Lack of sleep, both mental and physical stress and even some food allergies can also rouse the virus.

Denavir and Abreva creams are two products that hasten healing. Famvir, Zovirax and Valtrex are oral medicines that shorten the duration of a cold sore. If you have frequent outbreaks, your doctor can give you a prescription for one of those medicines to keep on hand. Use the medicine at the first inkling a sore is about to blossom.

L-lysine is an amino acid. It is not a drug. Amino acids are the building bricks of protein. Lysine apparently inhibits replication of herpes virus. Lysine-rich foods include eggs, chicken, milk and soy. Arginine, another amino acid, promotes herpes replication. Avoid foods with a high arginine content, like nuts, grains and chocolate.

The herpes pamphlet mostly deals with herpes-2 infection, the genital infection. Nevertheless, many things about the herpes-2 virus apply to the herpes-1 virus. Readers can order a copy by writing: Dr. Donohue – No. 1202, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.50 U.S./$6.50 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I went for a blood test, and my alkaline phosphatase was high. What is it? How can I lower it? – T.F.

Alkaline phosphatase is an enzyme. Every body cell has enzymes. They keep the cell’s assembly line moving at a rapid clip.

A rise in an enzyme level in the blood indicates that a particular organ or tissue has been injured. Alkaline phosphatase is found in bile ducts and bone. The trick is to find which of those structures is suffering. The alkaline phosphatase of bone origin can be separated from the alkaline phosphatase of bile ducts by a simple lab test. Separating the two enzymes narrows the search for the damaged structure. Your doctor has to do this for you.

Older people often have an elevated alkaline phosphatase due to Paget’s disease of bone. In that illness, there is rapid breakdown and buildup of bone. Quite often the process is limited to a section of one bone, and then it presents few problems.

There is nothing you can do on your own to lower the level of alkaline phosphatase.

I should also mention that levels can be higher than normal without indicating illness. Pregnant women have high levels because of the placenta’s production of the enzyme. Growing children, whose bones are rapidly enlarging, also have high levels. So do blood types B and O, for reasons I do not know.

DEAR DR. DONOHUE: I am a 75-year-old woman with a friend who takes Pilates exercise classes. She’s been trying to talk me into taking them, too. I haven’t exercised for 30 years, and I wonder if I could get any results from these exercises. My doctor says I can safely join the class. What do you think? – R.M.

You wonder what I’m going to say? I say take the class. Your doctor has given you permission, so your age and lack of exercise are not contraindications to your participation.

For readers unfamiliar with Pilates exercises, they are a group of 500 exercises during which participants change from one exercise position to the next with slow, fluid movements. Not all 500 exercises are done in one session.

These exercises keep your joints limber and increase strength. They strengthen bones by warding off osteoporosis. That, in turn, prevents broken hips. They also restore a sense of balance, something that evaporates with time.

A class with an instructor is perfect for a beginner. The instructor can spot any deviations from proper technique and provide the stimulus to keep at it.

Another selling point is that these exercises are not too strenuous for a 75-year-old woman who has not exercised for 30 years.

DEAR DR. DONOHUE: Would a dropped bladder cause back pain? – B.P.

es, it can. You can prop up a dropped bladder with a doughnut-shaped device called a pessary. The pessary fits around the uterus’s cervix. If the pain lessens, that’s pretty good evidence that the dropped bladder is its cause.

DEAR DR. DONOHUE: I take a three-mile walk at least three times a week. I do not have breakfast until after the walk. Is not eating defeating the purpose of walking, since my metabolism rate is not working? – S.R.

Your metabolism works fine without food in your stomach. Furthermore, the metabolic rate stays elevated for quite some time after exercise. You are covered on that front, too. If you think you cannot burn calories without food in the stomach, stop worrying. We all have plenty of fuel for exercise in calories stored as carbohydrate and fat.

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.

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