E.D.
Probiotics (acidophilus) are a beneficial bacteria that inhibits the growth of yeast. They are taken orally, often in capsules for adults and powder that can be added to juice or milk for little ones. There are varieties made in powder form just for children and babies, sold at places like Central Market and Whole Foods or health/vitamin stores.
This is also a good supplement for regular use, not just combatting yeast infections, because the amount of sugar in our diets promotes yeast growth, and this is a good regular defense to help our digestive systems overall. I would do more research on it (candida overgrowth, probiotics), as there's volumes available covering the topic.
Good luck! By the way, kellymom.com gives tips on this very thing and several ways to treat it.