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Yeast Infections: Common Causes

Yeast infections are very common: three out of four women have at least one during their lives. What causes vaginal yeast infections? Candida yeast normally live in the vagina. But certain conditions set up an ideal environment for the yeast to "overgrow" out of balance and cause a yeast infection.

What Puts You at Risk for a Yeast Infection?


  • Antibiotics. Taking antibiotics is one of the most common causes of a vaginal yeast infection. Antibiotics and some other medications change the level of bacteria and other organisms in the vagina -- such as the bacteria lactobacillus acidophilus, which normally helps keep yeast cells under control. Medications can also change vagina's acidity, called the "Ph balance," allowing yeast to overgrow.
  • Pregnancy. Pregnant women have high levels of estrogen, which can cause a yeast infection during pregnancy.
  • Other changes in hormone levels. Taking hormone replacement therapy (HRT) or birth control pills changes the balance of hormones in the body, especially estrogen and progesterone. Just as in pregnancy, higher estrogen levels can cause yeast infections. Some women find they're more likely to get yeast infections at specific times in their menstrual cycles.
  • Diabetes. Poorly managed diabetes -- letting blood sugar levels get too high -- can lead to yeast infections. The yeast flourish on excess glucose in the body.
  • A weakened immune system. Having a condition that weakens the immune system, such as HIV or AIDS, can prevent the body from fighting off a yeast infection. Some women find that being overly stressed or having a cold or flu, which already taxes the immune system, can raise their risk of a yeast infection.
  • Douching upsets the natural balance of yeast and bacteria that lives in the vagina and kills off some of the healthy bacteria that normally prevent yeast from overgrowing.

Having an occasional yeast infection is an uncomfortable, though rarely serious, problem. But see your doctor if you have frequent, repeat vaginal yeast infections, because this can be an early sign of HIV.

WebMD Medical Reference

Reviewed by Mikio A. Nihira, MD on August 22, 2012

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