Good germs sounds like a contradiction, but that's what probiotics are, says Jose Saavedra, M.D., associate professor of pediatrics at Johns Hopkins University Medical School. Here's how they can help:

Benefits: Probiotics restore balance to the digestive system and ease diarrhea (from a bug or antibiotics). Given in the early months, some may even help prevent allergies. One study found that probiotic drops relieved colic.

Where to get them: Breastfed babies naturally have a higher level of good bacteria. Bottle-fed babies can drink the probiotic-fortified Nestlè Good Start Natural Cultures formula, and Beech Nut's Good Morning and Good Evening baby foods contain prebiotics, a type of fiber that fosters the growth of probiotics. Older babies can get them from certain kinds of yogurt and yogurt drinks (try Stonyfield Farms products). And some doctors recommend probiotic supplements (Florastor Kids, Culturelle for Kids) for antibiotic-related diarrhea. Always talk to your doctor, however, before switching formulas or giving supplements.