DEAR DR. DONOHUE: I have had recurrent bacterial vaginosis for more than two years. I have been treated with both oral and vaginal medicines.

As soon as I stop taking them, the infection returns. Will I have to stay on mediation for the rest of my life? – M.H.

ANSWER: Bacterial vaginosis is the most common vaginal infection. The population of normal vaginal bacteria becomes displaced by a mixture of troublemaking bacteria.

Why it happens is an unanswered question. It has a habit of returning, but why it does so is another unanswered question. The result of the takeover by the new bacteria gives rise to a profuse, gray to milky-white discharge with a foul odor. The vagina becomes irritated.

With a microscopic exam of the discharge and by noting its odor, doctors can make an accurate diagnosis without lots of other tests. Metronidazole is an antibiotic that can usually put an end to bacterial vaginosis. It comes either in a tablet or in a gel that’s applied directly to the vagina. Such a succession of recurrences as you have had is not usual. How long do you take the medicine?

Ordinarily, metronidazole is prescribed for a week. However, you would be better off taking it for two weeks and then going on a maintenance program.

During maintenance therapy, you use medicine only twice a week, and you could switch to the gel form so you won’t upset your digestive tract with prolonged use of oral medicine. Another newer medicine applied directly to the vagina is Clindesse cream.

It contains the antibiotic clindamycin, which has also long been used in oral form for bacterial vaginosis. If metronidazole fails you, then this might be an option. It sounds logical to treat a person’s partner to avoid reinfection. With bacterial vaginosis, it’s been demonstrated that partner treatment doesn’t stop recurrences. The booklet on vaginal infections describes the common ones and their treatments.

Readers can obtain a copy by writing: Dr. Donohue – No. 1203, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: Several years ago I had an MRI of my sinuses.

The doctor told me I had an empty sella. I learned that meant my pituitary gland had shrunk. Can you give me information on what bearing this has on my health? – M.H.

ANSWER: You can join the ranks of many people who have had an MRI scan of the skull for some completely different reason and then were told they had an empty sella.

The sella is a saddle-shaped bone in which the pituitary gland sits. The pituitary gland, at the base of the brain, is a small gland, only about two-fifths of an inch in all dimensions. It is, however, a giant gland in its many responsibilities. It’s the body’s master endocrine gland. When an MRI doesn’t show the pituitary gland in the sella, a person is said to have an empty sella.

If people with an empty sella have no symptoms and no signs of endocrine gland deficiencies, the conclusion is that there is a thin rim of pituitary gland left that can’t be seen on the MRI but that fills all the gland’s functions.

For most people, an empty sella has no bearing on their health.

DEAR DR. DONOHUE: Some time ago, you wrote about pemphigoid. In 2002, blisters appeared on my left knee. The doctor thought it was an allergy.

The blisters began to multiply on both legs, and I saw a dermatologist, who performed a biopsy and put me on prednisone. The biopsy revealed bullous pemphigoid.

Prednisone didn’t work for me, so the doctor discussed the matter with a colleague, who suggested using CellCept. The blisters were gone in a short time.

I hope this information will help others. – P.T.

ANSWER: Are you sure I’m the one who wrote about bullous pemphigoid? I can’t find the item, but it’s a subject that merits mention.

Bullous pemphigoid is a skin condition that features the outbreak of large blisters, most often on the thighs, forearms, trunk, under the arms and on the groin. It can appear at any age, but the onset usually occurs between the ages of 65 and 75 and in young children.

It’s another example of an autoimmune disease, one where the immune system turns on the skin. In a few, it can be deadly in the first year of an outbreak. Frequently, in five to six years, the illness burns out without leaving permanent damage.

Cortisone drugs, like prednisone, either applied directly to the skin or taken by mouth are the drugs usually prescribed. Azathioprine, a drug that can control the immune attack, is another often-used medicine for bullous pemphigoid.

I confess I have never heard of CellCept used for it. It’s a medicine that prevents rejection of transplanted tissues or organs. I’m glad it did such a good job for you.

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