Yeast infections occur mainly in women who are menstruating (having monthly periods). They are less common in postmenopausal women who do not take estrogen and in girls who have not yet started menstruating.

SYMPTOMS — Itching of the vulva is the most common symptom of a vaginal yeast infection. Women may also note pain with urination, vulvar soreness or irritation, pain with intercourse, or reddened and swollen vulvar and vaginal tissues. There is often little or no vaginal discharge. If present, discharge is typically white and clumpy (curd-like), although it may be thin and watery in some cases. Symptoms of a yeast infection are similar to a number of other conditions, including bacterial vaginosis (a bacterial infection of the vagina), trichomoniasis (a sexually transmitted infection), and contact or allergic dermatitis (a skin reaction to an irritating or allergic substance).

CAUSE — Candida albicans is a fungus that normally lives on the skin and mucous membranes (mouth, nose, vagina). Normally, Candida causes no symptoms. However, when the skin or mucous membranes undergo changes due to medications, injury, or stress to the immune system, Candida may multiply and cause the symptoms described above.

RISK FACTORS — In most women, there is no underlying disease or event that leads to a yeast infection. There are several risk factors that may increase the chances of developing an infection, including:

• Antibiotics — Most antibiotics kill a wide variety of bacteria, including those that normally live in the vagina. These bacteria protect the vagina from the overgrowth of yeast. Some women are prone to yeast infections while taking antibiotics.

• Hormonal contraceptives (eg, birth control pills, patch, and vaginal ring) — The risk of yeast infections may be higher in women who use birth control methods containing estrogen.

• Contraceptive devices — Vaginal sponges, diaphragms, and intrauterine devices (IUDs) have been associated with a higher risk of yeast infection. Spermicides have not, although spermicides frequently cause vaginal irritation.

• Immunosuppression — Yeast infections are more common in people who have a weakened immune system due to infection with HIV or use of certain medications (steroids, chemotherapy, post-organ transplant medications).

• Pregnancy — Vaginal discharge can become more noticeable during pregnancy, although yeast infection may not always be the cause.

• Diabetes — Women with diabetes are at higher risk for yeast infection, especially when blood glucose levels are persistently higher than normal.

• Sexual activity — Vaginal yeast infections are not considered to be a sexually transmitted infection. They can occur in women who have never been sexually active but are more common in women who are sexually active. Yeast infections are no more frequent in women who have sex frequently, but they may develop more frequently in women who receive oral sex.

DIAGNOSIS — Diagnosis of a vaginal yeast infection requires that a healthcare provider take a medical history, perform a physical examination, and perform diagnostic testing. A physical examination is the most accurate way of determining the cause of abnormal vaginal discharge. Do not begin treatment at home before being examined because self-treatment can make it more difficult to make an accurate diagnosis. During the examination, the healthcare provider will examine the entire outer genital area and will perform an internal examination. He/she will take a sample of the discharge to test for infection. Further testing with a yeast culture may be used for a woman who has symptoms of a yeast infection but no evidence of yeast on wet mount. Culture is also useful for women with recurrent or persistent signs and symptoms who have a negative wet mount or do not respond to treatment. Yeast culture and sensitivity can determine if less common species of yeast are present.

Self-diagnosis — Women with symptoms of vulvar itching or vaginal discharge frequently assume that their symptoms are related to a yeast infection and treat themselves with an over-the-counter treatment. In one study, only 11 percent of women accurately diagnosed their infection; women with a previous yeast infection were only slightly more accurate (35 percent correct). Incorrect self-diagnosis and treatment can delay receiving the correct diagnosis and treatment and wastes money on improper treatment, which frequently causes further irritation of the vulva and vagina.

RECURRENT VAGINAL YEAST INFECTIONS — Between 5 and 8 percent of women have recurrent yeast infections, defined as more than four infections per year. Risk factors for recurrent infection include the use of panty liners, pantyhose, or sexual lubricants, or the consumption of cranberry juice. Avoidance of these products may reduce the frequency of infection in some women. There is no evidence that eating yogurt or other products containing live Lactobacillus acidophilus, or applying these products to the vagina is of any benefit in women with recurrent vaginal yeast infections.

Diagnosis — As with initial yeast infections, it is important to correctly diagnose recurrent yeast infections. A woman who has frequent signs and symptoms of vulvar or vaginal irritation or itching should be seen by a healthcare provider to ensure that her symptoms are caused by yeast rather than other common problems (eg, other vaginal infections, allergic reaction or sensitivity, eczema). As with initial infections, self-diagnosis is not accurate enough to recommend treatment.

Treatment — Women with recurrent infections are usually given a longer course of treatment for infections, between 10 to 14 days for a topical (cream or suppository) medication or fluconazole 150 mg by mouth with a second and third dose 3 and 6 days later. Preventive treatment may be recommended after the infection has resolved; this may include fluconazole (150 mg orally once per week) or clotrimazole (500 mg vaginal suppositories administered once per week).

Treatment of a sexual partner — Vaginal yeast infections are not a sexually transmitted infection, although the infection may rarely be passed from one partner to another. Most experts do not recommend treatment of a sexual partner.