What is a Yeast Infection? - Causes, Symptoms & Treatment

Instructor: Ashli Wilson

Ashli has a Master's Degree in Biology and has taught biology at different grade levels including college, elementary, and middle school.

Yeast infections are extremely common in women of all ages and can occur regardless of sexual activity. That's why it's important to know what causes yeast infections, as well as the symptoms and treatment options.

The Basics of Yeast Infections

About 75% of women experience at least one yeast infection in their lifetime, and fortunately these infections are very easy to diagnose and treat. Yeast infections are caused when there is too much fungus in the vagina, a fungus called Candida that is found in low amounts on the skin and in the vagina of the human body. In low amounts, Candida does not cause illnesses in the vagina, but an overgrowth of Candida may lead to yeast infection. Let's discuss what can cause too much Candida.

What Causes Overgrowth of Candida in the Vagina?

Causes of yeast infections include taking antibiotics, increased moisture in the vagina from douching or daily activities, and uncontrolled type 2 diabetes. Let's take a look at each cause of yeast infections and exactly how each fosters an environment for Candida overgrowth.


A woman is prescribed antibiotics to target and kill bacteria in her body that is causing an illness. Antibiotics will kill the bacteria causing her illness but can also kill the Lactobacillus in the vagina. Lactobacillus is a bacterium that helps to keep Candida in balance, but decreased amounts of Lactobacillus leads to increased amounts of Candida resulting in a yeast infection. Lactobacillus creates a slightly acidic environment in the vagina, which keeps Candida from overgrowing. Reduction of Lactobacillus decreases the acidity of the vagina, promoting an overgrowth of Candida. If the antibiotics kill Lactobacillus, the vagina becomes less acidic, spawning more growth of Candida and triggering a yeast infection. When taking antibiotics, women should take probiotics or eat yogurt that contains Lactobacillus to maintain the normal level of bacteria in the vagina.

Excess Moisture

The vagina is a naturally moist environment, but excess moisture encourages Candida growth. Fungi flourish in moist environments, so if the vagina has more moisture than usual, a yeast infection can occur. Increased moisture in the vagina from douching and daily activities can cause an overgrowth of Candida. Douching is the act of rinsing out the vagina with a solution. Douches are sold over the counter, and some women use douches to get rid of unwanted odor and feel clean. It is recommended that women avoid douching and wash with mild soaps and warm water to get rid of unwanted odor. The additional moisture in the vaginal area from daily activities, such as working out and swimming, can also induce Candida overgrowth, which is why it is recommended that women wear cotton underwear and change out of wet bathing suits and workout clothes as soon as possible.

Type 2 Diabetes

Increased levels of Candida in the vagina are more common in women with uncontrolled type 2 diabetes. Type 2 diabetes is caused when your body does not produce enough insulin to keep your blood sugar at a normal level. Women with uncontrolled type 2 diabetes have higher levels of sugar in their bodies, which means these women have more sugar in their vaginas. Candida flourishes in environments with moisture and sugar, so women with type 2 diabetes should maintain a normal blood sugar level to prevent increased amounts of sugar in the vagina.

Now that we know what causes a yeast infection, let's discuss the signs and symptoms of yeast infections.


The most common symptom of a yeast infection is vaginal itching, but other symptoms include burning, redness, and swelling of the vagina. Women may also experience cottage cheese-like discharge that does not have an odor and pain during sexual intercourse and urination. Women who have not had a yeast infection before are encouraged to see a doctor for diagnosis before taking any treatments to ensure a sexually transmitted infection is not being self-diagnosed as a yeast infection. It is important to note that yeast infections are not sexually transmitted infections, and women who are not sexually active can be diagnosed with a yeast infection.

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