Purity expiry date got baby sick

I went and got my child 2 bottles of purity and I went home. Where I gave my son the one bottle. Later he started to get sick and we did not know what it can be that making him so sick. As we had to start telling what he had to drink and eat, where he played. Then when we took the purity we saw that it has already expired in August. How can management allow for food to stay in the store after the expiry date. Bad management and don't have any control over his team. I am not going to leave it.