My 19-year-old daughter has a yeast infection that comes back whenever she is not on her period. Her doctor told her to use Monistat 7 and go off the birth control pill, as the pill can sometimes cause this to happen. Is this true? She has diabetes and is living with her boyfriend and does not want to get pregnant. She complains that the infection is really irritating to the point that she scratches until she bleeds. She was given oral medication two months ago, and it did not work. Could her boyfriend be reinfecting her?

M.B.

Vaginal yeast infections are among the most common infections of young women, and several other disorders cause very similar symptoms. It is estimated that these so-called "vulvo-vaginal symptoms" account for more than 10 million doctor visits per year in the United States.

Vulvo-vaginal yeast infections, usually caused by the fungus Candida albicans, affect up to 75 percent of all women at some point in their lives. There are several known risk factors for these infections, including high levels of estrogen. This is why young girls and postmenopausal women have fewer yeast infections than women of childbearing age. It has also been shown, at least in some studies, that birth control pills containing high levels of estrogen may increase the risk as well. Using vaginal sponges and intrauterine devices can also increase the risk of yeast infections.

The treatment of vaginal Candida infections is usually straightforward. Fluconazole (trade name Diflucan), an oral antifungal medicine, usually cures the infection with a single dose. This treatment has the benefit of convenience, but it does have rare side effects. Several vaginal preparations appear to be equally effective. Patients with especially severe infections sometimes require several days of oral therapy or several weeks of vaginal treatment with an antifungal cream.

Women with recurrent yeast infections should be evaluated for a few underlying conditions, including diabetes mellitus. I assume that your daughter is not on immunosuppressive drugs such as prednisone. I also test my patients with recurrent infections for HIV, the virus that causes AIDS. It is an uncommon cause of recurrent yeast infections, but it certainly must not be overlooked. Next, some of the vaginal discharge should be cultured (sent to a laboratory to grow any microbes present). This will confirm the diagnosis, as there are other infections and inflammatory disorders that can mimic yeast infections. In addition, I would want to know if the causative fungus really is Candida albicans. If she is infected with another type of yeast, Candida glabrata, she has a difficult problem. This organism is far less susceptible to the usual treatments for yeast infections.

If your daughter is infected with the usual Candida albicans, and if the strain is susceptible to fluconazole, I would treat her with that drug. She may simply need a longer course of treatment than usual. If the infection still recurs, several methods can prevent future problems. Her doctor may prescribe topical boric acid and attempt to eradicate the organism from her gastrointestinal tract, where Candida often resides. In addition, I agree with stopping birth control pills, at least for a while. (If condoms are used correctly, they are effective birth control. They also have the benefit of preventing HIV infection and other sexually transmitted diseases. Birth control pills are more effective in preventing pregnancy, but they have no effect in preventing infections.)

It has been shown that a male partner can be infected, but in your daughter's case, I do not think there is much point in treating her partner. Given what you have told me, I don't think he is the source for your daughter. When the partner is the source, I would expect the woman to be free of disease for some time between recurrences. It sounds like your daughter is not well for very long at all between her infections.