Thrush is caused by forms of a fungus called Candida. A small amount of this fungus lives in your mouth most of the time. It is usually kept in check by your immune system and other types of germs that also normally live in your mouth.
However, when your immune system is weak, the fungus can grow. The following factors can increase your chances of getting thrush:
Receiving chemotherapy for cancer or drugs to suppress your immune system
Taking steroid medicationsm
Thrush is commonly seen in infants. It is not considered abnormal in infants unless it lasts longer than a couple of weeks.
Candida can also cause yeast infections in the vagina.
People who have diabetes and have high blood sugar levels are more likely to get thrush in the mouth (oral thrush), because the extra sugar in your saliva acts like food for Candida.
Taking high doses of antibiotics or taking antibiotics for a long time also increases the risk of oral thrush. Antibiotics kill some of the healthy bacteria that help keep Candida from growing too much.
People with poorly fitting dentures are also more likely to get thrush.
Thrush appears as whitish, velvety sores in the mouth and on the tongue. Underneath the whitish material, there is red tissue that may bleed easily. The sores can slowly increase in number and size.
Signs and tests
Your doctor or dentist can almost always diagnose thrush by looking at your mouth and tongue. The sores have a distinct appearance.
If the diagnosis is not clear, one of the following tests may be performed to look for Candida:
For thrush in infants, treatment is often NOT needed. It usually gets better on its own within 2 weeks.
If you develop a mild case of thrush after taking antibiotics, eating yogurt or taking over-the-counter acidophilus capsules can help.
Use a soft toothbrush and rinse your mouth with a diluted 3% hydrogen peroxide solution several times a day.
Good control of blood sugar levels in persons with diabetes may clear a thrush infection.
Your doctor may prescribe an antifungal mouthwash (nystatin) or lozenges (clotrimazole) to suck on if you have a severe case of thrush or a weakened immune system. These products are usually used for 5 - 10 days. If they don't work, other medication may be prescribed.
If the infection has spread throughout your body or you have HIV/AIDS, you may need stronger medications, such as fluconazole (Diflucan) or itraconazole (Sporanox).
Thrush in infants may be painful, but it is rarely serious. Because of discomfort, it can interfere with eating. If it does not get better on its own within 2 weeks, call your pediatrician.
In adults, thrush that occurs in the mouth can be cured. However, the long-term outlook depends on your immune system and the cause of the immune problem.
If you have a weakened immune system (for example, if you are HIV-positive or receiving chemotherapy), Candida can spread throughout your body, causing infection in your:
Your infant has had thrush-like sores in the mouth for at least 2 weeks.
Your infant is eating poorly due to the sores.
You are a teen or adult with thrush-like sores.
You have pain or difficulty swallowing.
You have symptoms of thrush and you are HIV positive, receiving chemotherapy, or you take medications to suppress your immune system.
If you get thrush often, your doctor may recommend taking antifungal medication on a regular basis to avoid repeat infections.
If an infant with thrush is breastfeeding, talk to your doctor about ways to prevent future infections, such as an antifungal medication. Sterilize or throw out any pacifiers. For bottle-fed babies with thrush, throw out the nipples and buy new ones as the baby's mouth begins to clear.
To prevent the spread of HIV infection, follow safe sex practices and use precautions when working with blood products.
Edwards JE Jr. Candida species. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 257.
Kauffman CA. Candidiasis. In: Goldman L, Ausiello D, eds. Cecil Textbook of Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007:chap 359.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.