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

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.