Children and dogs enjoy playing together but just as you would not allow a small child to play unsupervised near water, the same should be true when they play with the family pet. Play can get over zealous; a dog may knock a toddler over or a child might poke in the eye. If a child gets hurt in play it will either cry or lash out and a dog is no different. If a dog feels threatened, tormented or frightened, it will defend itself.