Common Causes of Yeast Infections

Reviewed by Traci C. Johnson, MD on February 04, 2021

Did you know that yeast infections can happen anywhere in the body, including your mouth and skin? They can also get into your blood.

More than 20 types of candida (yeast) normally live in your GI tract, on your skin, and in your mucus membranes without causing any problems. Their growth is kept in check by bacteria.But when something happens to kill off the bacteria or change the conditions where yeast lives, it can multiply and cause mild to serious infections.

This article touches on the most common causes.



People who wear dentures, particularly those who also have diabetes, may be more likely to get thrush. Clean your dentures thoroughly each night to prevent infection.

Douches and Vaginal Sprays

Some products can change the acidity level in your vagina. That encourages the growth of yeast and can remove the helpful bacteria that keep yeast at bay.


The change in estrogen and progesterone levels in women who are pregnant, breastfeeding, using hormone replacement therapy, or taking birth control with estrogen can lead to vaginal yeast infections.


Wearing underwear (or tight jeans or a wet swimsuit) that doesn’t breathe can increase body heat and moisture in the vagina. This creates conditions yeast likes to grow in. Choose underwear with a cotton crotch, and change out of swimsuits and workout clothes as soon as possible.

Diaper Rash

Change babies’ diapers often. Soiled and wet diapers can lead to diaper rash. Once the skin is irritated, a yeast infection can set in.

Other Medical Causes

  • Diabetes. If your diabetes isn’t well-controlled, the increase in sugar in the mucus membranes (moist tissues) of your vagina can create a fertile environment for yeast to grow.
  • Weakened immune system. If you have HIV/AIDS or another condition that hampers your immune system, your body can’t fight off infections as well. If you’re getting cancer treatment or have had an organ transplant, your chances of getting yeast infections like thrush or invasive candidiasis are higher.
  • Hospitalization. When yeast enters the bloodstream, doctors call that invasive candidiasis. It’s most common in people who have recently been admitted to a hospital or live in another type of health care facility, such as a nursing home.
WebMD Medical Reference



CDC: “Candidasis.”

American Congress of Obstetricians and Gynecologists: “Vaginitis.”

National Health Service (U.K.): “Oral Thrush in Adults.”

American Dental Association, “Thrush.” “Vaginal Yeast Infection” “Diaper Rash.”


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