Thrush is the common name for an overgrowth of a specific kind of yeast in your mouth. There are several underlying conditions that make you more susceptible to thrush, and some medications can also increase your chances of getting thrush. Probiotics may help prevent thrush, but there's no scientific evidence they can treat it.
Thrush is caused by a group of fungi called Candida. You can get candidiasis -- a yeast overgrowth -- in many different parts of your body. Depending on where the yeast are growing, symptoms vary. Oral thrush symptoms include a thick white coating on the tongue that bleeds if you scratch it off. Your throat and mouth may also feel sore and scratchy. You're at increased risk for thrush if you have a suppressed immune system -- individuals with HIV have a high incidence of thrush, for instance -- and if you are taking immune-suppressing drugs such as certain steroids. You're also at increased risk if you're on antibiotics, since they kill the friendly bacteria that help control the yeast population in your body.
Probiotics are nonpathogenic bacteria; this means they don't harm you. They naturally grow in certain areas of your body, including your digestive tract. Species of probiotic bacteria include Lactobacillus acidophilus, which helps to ferment milk into yogurt. Eating yogurt and other dairy products that contain Lactobacillus acidophilus increases the population of healthy bacteria in your intestine. Because probiotic bacteria compete with disease-causing bacteria, they help keep your digestive tract infection-free. They also help control the population of Candida because increase the acidity of your digestive tract.
There is no scientific evidence to suggest that you can treat an active thrush infection with probiotics. Although probiotics can help prevent overgrowth of harmful bacteria, they are not able to fight off disease-causing bacteria once they've taken over. If you have a thrush infection, see your doctor. Treatment of thrush generally involves use of an antifungal medication, typically a lozenge or liquid. Infants sometimes get oral thrush from exposure to yeast on the mother's nipples during breastfeeding. But PubMed Health explains that thrush typically clears up on its own in the very young. Still, you should see your pediatrician if you think your baby has thrush.
While probiotics are not useful for treating thrush, there's good scientific evidence to indicate that probiotics may prevent thrush. If you're taking a steroid or are taking antibiotics, you might want to consider using a probiotic supplement. In a 2003 article in "Alternative Medicine Review," Dr. Jeanne Drisko and colleagues note that probiotics, including Lactobacillus acidophilus, help prevent overgrowth of Candida in the gastrointestinal tract. A 2001 study published in the "Journal of the American Dietetic Association" by Lori Kopp-Hoolihan suggests a similar effect, and further notes that probiotics can help support the immune system, which also has a preventative effect against thrush.