Call the doctor anytime a baby younger than 3 months has diarrhea. Breastfed babies should continue to nurse as often as possible. Some doctors say that the excess saliva from teething may lead to a mild case of loose stools. Changes in a child's diet due to the introduction of solid foods may also be the culprit. When appetite returns, offer older kids their regular meals, which will help them recover faster and lose less weight.