Causes
By Mayo Clinic staffOral thrush and other Candida infections can occur when your immune system is weakened by disease or drugs such as prednisone, or when antibiotics disturb the natural balance of microorganisms in your body.
Normally your immune system works to repel harmful invading organisms, such as viruses, bacteria and fungi, while maintaining a balance between "good" and "bad" microbes that normally inhabit your body. But sometimes these protective mechanisms fail, which can allow an oral thrush infection to take hold.
These illnesses may make you more susceptible to oral thrush infection:
- HIV/AIDS. The human immunodeficiency virus (HIV) — the virus that causes AIDS — damages or destroys cells of your immune system, making you more susceptible to opportunistic infections that your body would normally resist. Repeated bouts of oral thrush may be the first sign of an HIV infection.
- Cancer. If you have cancer, your immune system is likely to be weakened from the disease and from treatments, such as chemotherapy and radiation. Both the disease and treatments can increase your risk of Candida infections such as oral thrush.
- Diabetes mellitus. If you have untreated diabetes or the disease isn't well controlled, your saliva may contain large amounts of sugar, which encourages the growth of candida.
- Vaginal yeast infections. Vaginal yeast infections are caused by the same fungus that causes oral thrush. Although a yeast infection isn't dangerous, if you're pregnant you can pass the fungus to your baby during delivery. As a result, your newborn may develop oral thrush.
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- Candidiasis. American Academy of Pediatrics Redbook. http://aapredbook.aappublications.org. Accessed April 27, 2011.
- Kauffman CA. Clinical manifestations of oropharyngeal and esophageal candidiasis. http://www.uptodate.com/home/index.html. Accessed April 21, 2011.
- Is thrush causing my sore nipples? La Leche League International. http://www.llli.org/FAQ/thrush.html. Accessed June 29, 2009.
- Diabetes and oral health. American Dental Association. http://www.ada.org/sections/scienceAndResearch/pdfs/patient_18.pdf. Accessed April 21, 2011.
- Clarkson JE, et al. Interventions for preventing oral candidiasis for patients with cancer receiving treatment. Cochrane Database of Systematic Reviews. 2007;(1): CD003807.
- Pienaar ED, et al. Interventions for the prevention and management of oropharyngeal candidiasis associated with HIV infection in adults and children. Cochrane Database of Systematic Reviews. 2010;(11):CD003940.


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