Health A-Z

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Harvard Medical School

Candidiasis

What Is It?

Candidiasis is an infection caused by Candida fungi, especially Candida albicans. These fungi are found almost everywhere in the environment. Some may live harmlessly along with the abundant "native" species of bacteria that normally colonize the mouth, gastrointestinal tract and vagina. Usually, Candida is kept under control by the native bacteria and by the body's immune defenses. If the mix of native bacteria is changed by antibiotics, the body moisture that surrounds native bacteria can also have subtle changes in its acidity or chemistry. This can cause yeast to grow and to stick to surfaces, so that the yeast causes symptoms. Candida infections can cause occasional symptoms in healthy people. If a person's immune system is weakened by illness (especially AIDS or diabetes), malnutrition, or certain medications (corticosteroids or anticancer drugs), Candida fungi can cause symptoms more frequently. Candidiasis can affect many parts of the body, causing localized infections or larger illness, depending on the person and his or her general health.

Types of candidiasis include:

• Thrush — Thrush is the common name for a mouth infection caused by the Candida albicans fungus. It affects moist surfaces around the lips, inside the cheeks, and on the tongue and palate. Thrush is common in people with diseases such as cancer and AIDS, which both suppress the immune system. Thrush can develop in people with normal immune systems, too, particularly in people with diabetes or long-lasting irritation from dentures.

• Esophagitis — Candida infections of the mouth can spread to the esophagus, causing esophagitis. This infection is most common in people with AIDS and people receiving chemotherapy for cancer.

• Cutaneous (skin) candidiasis — Candida can cause skin infections, including diaper rash, in areas of skin that receive little ventilation and are unusually moist. Some common sites include the diaper area; the hands of people who routinely wear rubber gloves; the rim of skin at the base of the fingernail, especially for hands that are exposed to moisture; areas around the groin and in the crease of the buttocks; and the skin folds under large breasts.

• Vaginal yeast infections — Vaginal yeast infections are not usually transmitted sexually. During a lifetime, 75% of all women are likely to have at least one vaginal Candida infection, and up to 45% have 2 or more. Women may be more susceptible to vaginal yeast infections if they are pregnant or have diabetes. The use of antibiotics or birth control pills can promote yeast infections. So can frequent douching.

• Deep candidiasis (for example, candida sepsis) — In deep candidiasis, Candida fungi contaminate the bloodstream and spread throughout the body, causing severe infection. This is especially common in newborns with very low birth weights and in people with severely weakened immune systems or severe medical problems. In these people, Candida fungi may get into the bloodstream through skin catheters, tracheostomy sites, ventilation tubing, or surgical wounds. Deep candidiasis also can occur in healthy people if Candida fungi enter the blood through intravenous drug abuse, severe burns or wounds caused by trauma.