Staying Healthy Yeast Yeast is caused by a fungus that normally lives in the vagina.
Yeast only causes problems when it grows too rapidly.
Things that cause yeast to grow include some birth control pills, antibiotics, pregnancy, diabetes, HIV infection, douching, a woman's monthly period, and damp underwear. Yeast infections are very common. You can get medicine to treat yeast at the drug store or with a doctor's prescription. If you have never had a yeast infection before, see your health care provider before buying medicine. Most medicines are put in the vagina at night before you go to bed.