When Juanita was diagnosed with strep throat, her doctor prescribed an antibiotic to treat the infection. Juanita started to feel better soon after she took the medication — the pain in her throat subsided and her temperature returned to normal. But then she noticed an unusual discharge in her underwear. To make things worse, her vaginal area felt very itchy.

Juanita told her mom what was going on, and her mom took her back to the doctor's office. There, Juanita found out she had a yeast infection. Although she'd had been nervous about seeing a doctor for such a personal reason, she was relieved to find out that diagnosing and treating a yeast infection is simple and painless.

What Is a Yeast Infection?

A yeast infection, also known as candidiasis (pronounced: can-dih-DIE-uh-sis), is the name for a common infection caused by a yeast called candida albicans (a type of fungus).

Yeast infections usually occur in warm, moist parts of the body, such as the mouth and moist areas of skin. When they cause an infection in the vagina, it is known as vulvovaginal candidiasis.

Candida can overgrow for many reasons. Stress, pregnancy, and illnesses that affect the immune system may allow yeast to multiply, as can certain medicines. These include some birth control pills and steroids. Or if you're taking antibiotics, such as for strep throat, the antibiotics can kill "good" bacteria that also live in the body and normally keep the growth of candida in the vagina in check. Yeast also can flourish if a girl's blood sugar is high. Girls who have diabetes that isn't controlled are at a higher risk for yeast infections.

Many girls find that yeast infections tend to show up right before they get their periods because of the hormonal changes that come with the menstrual cycle. Clothing (especially underwear) that is too tight or made of materials like nylon that trap heat and moisture might make yeast infections more likely because yeast can thrive in this type of environment. Using scented sanitary products can irritate the vagina, and douching can upset the healthy balance of bacteria in the vagina. Both can make yeast infections more likely.

Yeast infections can happen to any girl, and they're not considered sexually transmitted infections — although they may be able to be spread from one sexual partner to the other. This is rare, though, and the partner of someone who has a yeast infection does not automatically have to be treated unless symptoms appear.

A doctor won't be able to tell how you got a yeast infection, but will be able to tell you if you really have one and, if so, how to treat it.

What Are the Symptoms?

Common signs and symptoms of yeast infections may include:

• itching and irritation in the vagina
• redness, swelling, or itching of the vulva (the folds of skin outside the vagina)
• a thick, white discharge that can look like cottage cheese and is usually odorless, although it might smell like bread or yeast
• pain or burning when urinating or during sex

If you have any of these symptoms, see your doctor or gynecologist. It's easy to confuse the symptoms of a yeast infection with those of some STDs and other vaginal infections. Your doctor can give you the right diagnosis so that you can be treated appropriately.

Do Guys Get Yeast Infections?

Guys don't get vaginal yeast infections, but they can get an infection of the head of the penis that is caused by the same candida that causes infections in girls. Guys who have diabetes or are on antibiotics for a long time are more prone to this infection. A guy with a yeast infection may not have any symptoms or the tip of the penis may become red and sore or itchy. Some guys might have a slight discharge or pain with urination as well.

Guys who are not circumcised need to take extra care to clean properly beneath their foreskins. The warm, moist folds of the foreskin are the perfect environment for yeast to thrive. Keeping the area clean and dry may help prevent an infection, but if symptoms do show up, a trip to the doctor will treat the infection.

How Can I Prevent Yeast Infections?

What you wear — or don't wear — can help you avoid a yeast infection. Yeast grows best in a warm, moist environment: think wet bathing suits, tight jeans, and stretchy exercise gear. Nylon underwear, pantyhose, and other synthetic materials that trap moisture also make yeast infections more likely.

Some girls may react to certain dyes or perfumes in soaps, bath gels or lotions, sanitary products, and laundry detergents. When the reaction causes irritation, that can set the stage for a yeast infection. Your best bet is to steer clear of perfumed products and to use mild and fragrance-free products when possible.

To help keep your vaginal area dry, try switching to all-cotton underwear and make sure you carefully dry off after you shower. If you can, wear cotton underwear to bed or don't wear any, and always wash and thoroughly dry your underwear before wearing them. Don't lounge around in a wet bathing suit and avoid jeans or pantyhose that are too tight.

Don't take leftover antibiotics or someone else's antibiotics if you think you have an infection. Only take antibiotics when and how they're prescribed for you. And if you have diabetes, make sure you keep your blood sugar levels under control.

Do I Need to See a Doctor?

Treating a yeast infection is simple. But it's still important to visit your doctor for the right diagnosis, since other infections can cause similar symptoms but require different treatments. Your doctor might take a urine sample — to rule out a urinary tract infection — and swab some discharge from your vagina to examine under a microscope.

If you do have a yeast infection, your doctor will probably prescribe a pill to swallow or a cream, tablet, or suppository to put in the vagina. When you get home, follow all the directions on the package carefully. Creams, tablets, and suppositories for the vagina often come with an applicator to help you place the medicine inside your vagina, where it can begin to work. If you're using a vaginal treatment, you should abstain from sex until the infection has been treated — these medications can weaken condoms and diaphragms.

All of these types of medication can clear up your symptoms in a couple of days and cure the infection within a week. It's important that you take the medicine for the whole time that your doctor prescribes. If you stop taking it too soon, the infection could come back. If you're not feeling better within a few days of finishing treatment, call your doctor.

Some of the medications used to treat yeast infections are available without a prescription in your local drugstore, but you shouldn't just buy one if you think you have a yeast infection. It's important to see a doctor for your diagnosis, because if you actually have another type of infection, it could get worse if not properly treated. Also, over-the-counter medicine should not be used by anyone younger than 12 or girls who might be pregnant without talking to a doctor first.

Yeast infections can be annoying, especially if they happen regularly. To help avoid them, follow your doctor's advice, wear cotton underwear, and try to wear loose-fitting clothes. Your body will thank you.

Reviewed by: Larissa Hirsch, MD
Date reviewed: January 2012