Dr. Greene's Answer
Nine months is okay for yogurt for most babies. Yogurt is a wonderful food. It is rich in calcium, and the active cultures have many health benefits. Kids with a strong family history of milk-protein allergies (not just lactose intolerance) may want to wait, however.
There have been a few studies suggesting that yogurt helps eczema and other similar conditions. The beneficial bacteria in yogurt seem to help by bringing the immune system to a good, middle level of alertness. It boosts immunity if it is low, and calms the immune system down if it is overexuberant.
As with any new food, the best way to tell if your child is allergic is to only introduce one new food at a time over a three- to five-day period, then watch for any symptoms: tummy upset, worsening rash, crankiness. Start your child with about two to four ounces a day. There are some yogurts designed specially for babies–it’s wonderful. (I sometimes eat it as a treat for myself!) Some yogurts are nonfat or low-fat–good for adults, but the full-fat is best for babies. For a low sugar alternative to flavored yogurts, try mixing plain yogurt with a small amount of baby food fruit or pureed fresh fruit.