There is harm in it IMO. There is plenty of research that shows that their digestive tract is simply not ready for anything but BM before 6months. And again as Christy said, you can't really take a 4month old reaching fro things as a sign they are ready fro food. At four months it's like someone just turned on the whole world. They reach for EVERYTHING. It's no indication that they are craving anything other than breast milk.