A vaginal yeast infection is a fungal infection that causes irritation, discharge and intense itchiness of the vagina and the vulva — the tissues at the vaginal opening.

Also called vaginal candidiasis, vaginal yeast infection affects up to 3 out of 4 women at some point in their lifetimes. Many women experience at least two episodes.

A vaginal yeast infection isn't considered a sexually transmitted infection. But, there's an increased risk of vaginal yeast infection at the time of first regular sexual activity. There's also some evidence that infections may be linked to mouth to genital contact (oral-genital sex).

Medications can effectively treat vaginal yeast infections. If you have recurrent yeast infections — four or more within a year — you may need a longer treatment course and a maintenance plan.

Yeast infection symptoms can range from mild to moderate, and include:

• Itching and irritation in the vagina and vulva
• A burning sensation, especially during intercourse or while urinating
• Redness and swelling of the vulva
• Vaginal pain and soreness
• Vaginal rash
• Thick, white, odor-free vaginal discharge with a cottage cheese appearance
• Watery vaginal discharge

Complicated yeast infection

You might have a complicated yeast infection if:

• You have severe signs and symptoms, such as extensive redness, swelling and itching that leads to tears, cracks or sores
• You have four or more yeast infections in a year
• Your infection is caused by a less typical type of fungus
• You're pregnant
• You have uncontrolled diabetes
• Your immune system is weakened because of certain medications or conditions such as HIV infection

When to see a doctor

Make an appointment with your doctor if:

• This is the first time you've had yeast infection symptoms
• You're not sure whether you have a yeast infection
• Your symptoms aren't relieved after treating with over-the-counter antifungal vaginal creams or suppositories
• You develop other symptoms

The fungus candida albicans is responsible for most vaginal yeast infections.

Your vagina naturally contains a balanced mix of yeast, including candida, and bacteria. Certain bacteria (lactobacillus) act to prevent an overgrowth of yeast.

But that balance can be disrupted. An overgrowth of candida or penetration of the fungus into deeper vaginal cell layers causes the signs and symptoms of a yeast infection.

Overgrowth of yeast can result from:

• Antibiotic use, which causes an imbalance in natural vaginal flora
• Pregnancy
• Uncontrolled diabetes
• An impaired immune system
• Taking oral contraceptives or hormone therapy that increase estrogen levels

Candida albicans is the most common type of fungus to cause yeast infections. Yeast infections caused by other types of candida fungus can be more difficult to treat, and generally need more-aggressive therapies.

Factors that increase your risk of developing a yeast infection include:

• Antibiotic use. Yeast infections are common in women who take antibiotics. Broad-spectrum antibiotics, which kill a range of bacteria, also kill healthy bacteria in your vagina, leading to overgrowth of yeast.
• Increased estrogen levels. Yeast infections are more common in women with higher estrogen levels — such as pregnant women or women taking high-dose estrogen birth control pills or estrogen hormone therapy.
• Uncontrolled diabetes. Women with poorly controlled blood sugar are at greater risk of yeast infections than women with well-controlled blood sugar.
• Impaired immune system. Women with lowered immunity — such as from corticosteroid therapy or HIV infection — are more likely to get yeast infections.

To reduce your risk of vaginal yeast infections, wear underwear that has a cotton crotch and doesn't fit too tightly.

It might also help to avoid:

• Tight-fitting pantyhose
• Douching, which removes some of the normal bacteria in the vagina that protect you from infection
• Scented feminine products, including bubble bath, pads and tampons
• Hot tubs and very hot baths
• Unnecessary antibiotic use, such as for colds or other viral infections
• Staying in wet clothes, such as swimsuits and workout attire, for long periods of time

To diagnose a yeast infection, your doctor may:

• Ask questions about your medical history. This might include gathering information about past vaginal infections or sexually transmitted infections.
• Perform a pelvic exam. Your doctor examines your external genitals for signs of infection. Next, your doctor places an instrument (speculum) into your vagina to hold the vaginal walls open to examine the vagina and cervix — the lower, narrower part of your uterus.
• Test vaginal secretions. Your doctor may send a sample of vaginal fluid for testing to determine the type of fungus causing the yeast infection. Identifying the fungus can help your doctor prescribe more effective treatment for recurrent yeast infections.

Treatment for yeast infections depends on the severity and frequency of your infections.

For mild to moderate symptoms and infrequent episodes, your doctor might recommend:

• Short-course vaginal therapy. Taking an antifungal medication for three to seven days will usually clear a yeast infection. Antifungal medications — which are available as creams, ointments, tablets and suppositories — include miconazole (Monistat 3) and terconazole. Some of these medications are available over-the-counter and others by prescription only.
• Single-dose oral medication. Your doctor might prescribe a one-time, single oral dose of fluconazole (Diflucan). Oral medication isn't recommended if you're pregnant. To manage more-severe symptoms, you might take two single doses three days apart.

See your doctor again if treatment doesn't resolve your symptoms or if your symptoms return within two months.

If your symptoms are severe, or you have frequent yeast infections, your doctor might recommend:

• Long-course vaginal therapy. Your doctor might prescribe an antifungal medication taken daily for up to two weeks, followed by once a week for six months.
• Multidose oral medication. Your doctor might prescribe two or three doses of an antifungal medication to be taken by mouth instead of vaginal therapy. However, this therapy isn't recommended for pregnant women.
• Azole resistant therapy. Your doctor might recommend boric acid, a capsule inserted into your vagina. This medication may be fatal if taken orally and is used only to treat candida fungus that is resistant to the usual antifungal agents.

No alternative medicine therapies have been proved to treat vaginal yeast infections. Some complementary and alternative therapies may provide some relief when combined with your doctor's care.

Talk to your doctor about what alternative treatments for vaginal yeast infection may be safe for you.

If you've been treated for a yeast infection in the past, your doctor may not need to see you and may prescribe a treatment over the phone. Otherwise, you're likely to see a family medicine doctor or gynecologist.

What you can do

• Make a list of any symptoms you've had and for how long.
• Write down key information, including other medical conditions and any medications, vitamins or supplements you're taking.
• Avoid using tampons or douching before your appointment.
• Make a list of questions to ask your doctor.

Questions to ask your doctor

• Do I need to take medicine?
• Are there any special instructions for taking the medicine?
• Are there any over-the-counter products that will treat my condition?
• What can I do if my symptoms return after treatment?
• How can I prevent yeast infections?
• What signs and symptoms should I watch out for?

During your appointment, don't hesitate to ask other questions as they occur to you.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, including:

• What vaginal symptoms do you have? How long have you had them?
• Do you notice a strong vaginal odor?
• Have you ever been treated for a vaginal infection?
• Have you tried over-the-counter products to treat your condition?
• Have you recently taken antibiotics?
• Are you sexually active?
• Are you pregnant?
• Do you use scented soap or bubble bath?
• Do you douche or use feminine hygiene spray?