A dog should have certain safe zones where the child is never allowed. Many dogs may become aggressive when food is involved. For example, a dog may bite a curious toddler who is reaching for a dog's bone or food. Likewise, a dog may aggressively go after a treat that a child is eating. So, make sure that when either your child or your dog is eating, that they are separated.
Some dogs are very protective of their toys.
They will often see baby's toys as their toys as well. To prevent any toy-related aggression, keep baby toys and dog toys separated, and dogs and babies separated when playing with their toys. I highly recommend Dr. Larry Lachman's book Dogs on the Couch . In it he deals with a dog-baby reconditioning treatment program in more detail. Online source for the safest and most effective pet flea control products.