Causes of Yeast Infections

Candidiasis is caused by one of four varieties of candida: Candida albicans, Candida glabrata, Candida tropicalis, and Candida krusei. By far the most common—causing nearly 80% of vaginal yeast infections—is Candida albicans. Most people have these organisms in the genital or intestinal tract to some degree at various times. It's the overgrowth of the fungus that causes problems.

There are a number of causes for this uncontrolled growth, usually related to some type of immune suppression. A significant change in diet can often be a trigger. In other instances, it's due to use of antibiotics to treat another infection, such as strep throat or acne. Broad-spectrum antibiotics such as penicillin or tetracycline can kill or suppress helpful bacteria in the genital tract, allowing yeast to grow unchecked.

It's even possible that an underlying disorder, like diabetes, is the root cause of the infection. When physicians see recurring yeast infections without another cause, they have to wonder about HIV disease. Because HIV (the virus that leads to AIDS) involves a lowering of the immune system, it could significantly impair a woman's ability to combat yeast.

Yeast infections can be passed back and forth between partners during intercourse. But because yeast is frequently present anyway, a sexual partner is more likely to pick up the infection if his or her immune system is also depressed.

Immunity can become depressed by a number of factors besides HIV infection. Illness or infection of any kind weakens one's immune system. Physical or mental stress can also wreak havoc, leaving the immune system less able to combat yeast infections. Lack of sleep, poor nutrition, and some medications can upset the body's balance, allowing yeast to thrive. Pregnant women also have a tendency to have more yeast infections, as the immune system becomes temporarily altered by hormonal surges.