When to supplement zinc to your baby depends on the specific situation. Generally, breast-fed babies are less likely to be deficient in zinc, while breast-fed babies may be deficient in zinc. If it is breast-fed, you can start to supplement zinc to your baby after four months. Don't blindly supplement zinc for your baby. You need to see if your child is really short of zinc. Generally, children with zinc deficiency will have symptoms such as yellow hair, poor appetite, anorexia, partial eclipse, slow growth and low resistance. It is best to take your child for a trace element examination to determine whether it is zinc deficiency and then choose the right product to supplement zinc.