Thrush (Candidiasis)

What Is It?

Thrush is the common name for a mouth infection caused by an overgrowth of the Candida fungus, which normally lives in many people's mouths. It is a surface infection that can affect the corners of the mouth, the insides of the cheeks, the tongue, palate and throat. Thrush is a common infection in babies. A newborn may acquire the Candida fungus during delivery, if its mother had an active vaginal yeast infection. Symptoms of thrush usually follow within 7 to 10 days after birth.

In older children or adults, episodes of thrush are triggered most frequently by diseases or drugs that affect the immune system, cancer chemotherapy, steroid therapy, or by treatment with antibiotics. Antibiotics trigger thrush by killing the mouth's normal population of bacteria. Once these normal bacteria are gone, Candida fungi are free to multiply and grow without competition. People with dry mouth have less saliva and are prone to developing thrush. Several medicines cause dry mouth as a side effect.

Certain people are more likely to get thrush. Examples include people with diabetes, and the elderly and debilitated. People who are malnourished or have illnesses that weaken immune defenses, such as cancer or HIV infection, are also at risk.


The first symptoms may be a bad taste in the mouth and decreased taste. Thrush causes curdlike white patches inside the mouth, especially on the tongue, palate (roof of the mouth and/or back of the throat) and corners of the mouth. If you try to scrape off the whitish surface of a patch, you will usually find a red, inflamed area that may bleed slightly. There may also be cracked, red, moist areas of skin at the corners of the mouth.

Sometimes thrush patches are painful, but often they are not. Infants who do have painful patches may be fussy, irritable and feed poorly.


Your dentist or physician usually diagnoses thrush by examining your mouth to look for white patches that scrape off with a tongue blade or gauze pad. If the diagnosis is in question, your doctor or dentist also may send a sample of these scrapings to a laboratory for testing. In certain cases, a biopsy is necessary. In this procedure, a small piece of skin is removed with a scalpel and examined in a laboratory.

In most patients, this is all that needs to be done for diagnosis. However, if you have frequent or persistent infections, your doctor or dentist may want to see if you have an undiagnosed medical illness, such as diabetes, cancer or HIV infection. In this case, blood tests or other types of diagnostic procedures may be necessary. Your doctor or dentist will ask about your history of these illnesses and about recent drug therapy.

Your doctor or dentist also will ask about your recent use of antibiotics or medications that suppress the immune system, such as steroids or cancer chemotherapy drugs. Your doctor or dentist also can determine if you are taking certain medicines that are associated with significant dry mouth.

Expected Duration

With proper medical treatment, most simple thrush infections can be cured in about 7 to 14 days.


You can help to prevent thrush by using antibiotics only as prescribed by your doctor and by seeing your dentist promptly for any mouth irritation or soreness around dentures. To prevent thrush in newborns, a pregnant woman should be checked by her doctor whenever she develops any white, cheesy vaginal discharge.

In patients with HIV or others who are taking drugs that suppress the immune system, doctors may prescribe antifungal drugs, such as clotrimazole (Mycelex), as a long-term measure to prevent thrush. However, because there is some evidence that Candida fungi eventually become resistant to these drugs, this preventive use is still controversial.


Doctors treat thrush with antifungal medications such as nystatin (Mycostatin, Nilstat), clotrimazole (Mycelex), ketoconazole (Nizoral), or fluconazole (Diflucan). For mild cases, a suspension of nystatin can be swished in the mouth and swallowed, or a clotrimazole lozenge can be dissolved in the mouth. For more severe cases, ketoconazole or fluconazole may be taken once a day for seven to 10 days. The corners of the mouth can be treated effectively with a nystatin ointment.

After successful treatment of thrush, your doctor may switch you from medicines that are suspected of causing significant dry mouth to medicines that are less drying. Only your doctor should change prescribed medicines that you are taking. Sometimes, medicines cannot be substituted for medical reasons. In this case, you should drink more water, and use mouth moisturizers and saliva replacements often.

When To Call A Professional

Call your doctor whenever curdlike white patches appear inside your mouth or in the mouth of your infant. Call your doctor immediately whenever any mouth irritation prevents your baby from feeding normally. Rarely, the fungus may affect tissue in the esophagus and cause difficulty swallowing. If this happens, you should phone your dentist or doctor. All patients with suppressed immune systems should be checked periodically for oral problems such as thrush.


In most otherwise healthy patients, a thrush infection that is treated properly goes away without permanently damaging the skin. The infection may not return as long as the patient remains healthy and well nourished. However, people with long-term illnesses or weakened immune systems may have frequent episodes of thrush. In some debilitated patients, the Candida fungus may even spread to the throat, causing Candida esophagitis, or to other parts of the body.

Additional Info

National Oral Health Information Clearinghouse
Bethesda, MD 20892-3500
Phone: (301) 402-7364
TTY: (301) 656-7581
Fax: (301) 907-8830

Centers for Disease Control and Prevention (CDC)
Oral Health Program
4770 Buford Highway, NE
MS F-10
Atlanta, GA 30341
Phone: (770) 488-6054
Toll-Free: (888) 232-3228
Fax: (888) 232-3299

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Reviewed by the faculty of Columbia University College of Dental Medicine