DEAR DR. DONOHUE: I am writing to you about my mom, who is 83. She has been treated for a venous ulcer of her lower right leg. For the past four months she has been seen at a hospital wound care center. She goes there once a week. The healing process has been very slow, and she is very discouraged. She reads your column and would like your opinion on this condition. – B.S.

ANSWER: Tell your mom not to become discouraged. Healing a venous leg ulcer takes six or more months.

Venous ulcers are open sores most frequently found at the ankle over the bone that juts outward on the legs’ inner side – the side that faces the other leg. They’re called “venous” because the problem starts with leg veins.

For blood to get from the legs back to the heart, nature had to devise an engineering system that overcomes gravity. The system involves leg veins. When blood begins its ascent in leg veins, vein valves close to prevent the blood from draining back down. If a person has faulty leg veins, blood accumulates in the lower leg veins. Vein pressure rises, and fluid oozes into the tissues of the ankle. The ankles swell, and an impermeable membrane forms in ankle tissues that blocks the passage of oxygen to the skin and superficial tissues. The skin breaks down, and an open sore forms.

Healing a venous ulcer requires facilitating the return of blood from the legs back to the heart. The best way to achieve that is always to sit with the legs elevated as high as they can be. In addition, your mother should lie down during the day with her legs propped up higher than her heart, so blood drains out of her legs. She should never sit with her legs dangling down to the floor.

Compression bandages prevent fluid from oozing out of leg blood vessels. Her doctors will let her know if they are appropriate for her.

With the help she’s getting, she should see success in the near future.

DEAR DR. DONOHUE: I have read articles saying most people don’t get enough vitamin D. The articles state that vitamin D can be obtained from skin exposure to the sun. My question is: How long is vitamin D stored in the body from sun exposure? A day? A month? A year? – J.F.

ANSWER: Vitamin D has a half-life of 10 days in the body. That means half the dose of vitamin D taken on day one will still be there on day 10. With a constant supply of the vitamin, we don’t run out of it.

The skin contains a substance, which, when exposed to the ultraviolet rays of the sun, becomes vitamin D. Ten to 15 minutes of sun exposure a couple of times a week can satisfy human vitamin D needs.

There is a catch here. Older people’s skin is less efficient at producing vitamin D, so sunlight can’t always supply them with enough of it. Furthermore, many older people get no sun exposure. And in the winter, in the northern United States and all of Canada, even healthy, active, outdoorsy people don’t get sufficient ultraviolet light to supply them with all the vitamin D they need.

Therefore, most older people need supplemental vitamin D. From age 51 to 70, the recommended daily allowance of vitamin D is 400 IU and, for those older than 70, it is 600 IU. Some feel that 1,000 IU is a more appropriate dose.

DEAR DR. DONOHUE: I have had a prolapsed uterus for 20 years. I use a pessary to keep it in place. I have a hard time removing it to clean it. Can’t I just keep it in? – M.B.

ANSWER: Pessaries are little devices inserted into the vagina to prop up fallen (prolapsed) uteruses, bladders and rectums. They come in many shapes, sizes and materials. They are foreign bodies and should be removed for cleaning, usually weekly. A silicone ring pessary can be folded in half, and it might be more easily inserted and removed for someone like you. Or a washable shoestring can be tied to the pessary to aid in its removal. Talk to your doctor about this.

DEAR DR. DONOHUE: I have taken tetracycline for acne for 26 years. I am now 40. Am I protected from other ailments and diseases like those from germs in untreated water, Lyme disease, E. coli or any of the other bacteria and viruses out there? Do I have to continue this medicine for life? – L.H.

ANSWER: The dose of tetracycline (an antibiotic) used for acne control is less than the dose used to kill bacteria. The answer to your question, therefore, is that you are not protected from bacterial germs. You’re also not protected from viruses. Antibiotics don’t kill viruses.

You can take the medicine for as long as you need to.

You’ve taken it for a considerable number of years. Is it working? There should come a time when you are eased off it or when a different medicine is prescribed.

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