Women and girls have yeast organisms that naturally occur in their vaginas. But sometimes too much yeast grows and can cause an infection. This can happen for different reasons. Sometimes, antibiotics—medicine taken for infections—can actually cause a yeast infection. That’s because some antibiotics kill the “good” bacteria that keep yeast from growing too much.

Changes in your hormone level—either from pregnancy or taking birth control pills—can also start yeast infections. And a girl can get a yeast infection if her vulva is damp from staying in a wet bathing suit or exercise clothes for a long time.

Some girls get yeast infections more than others. To reduce the chances of getting one, avoid wearing tight pants, non-cotton underwear and staying in wet clothes (a bathing suit or sweaty exercise clothes) for too long.

Usually, the first symptom of a yeast infection is redness and itching around the vulva and inside the vagina. There can also be white, thick, clumpy discharge that looks like cottage cheese. The vulva can be sore, too, or it may hurt to pee.

If you think you have a yeast infection, see your doctor or health care provider. These infections are usually treated with antifungal creams or suppositories (medicine inserted into the vagina). This medicine can be bought without a prescription at most drugstores or supermarkets.

Avoid having sex during a yeast infection. The medicine used to treat a yeast infection can weaken latex condoms. And although yeast infections are not considered a sexually transmitted disease, a girl can pass a yeast infection to her partner, though this is very rare.