Most kids would go out of their way to avoid eating garlic or onions, yet it is not unusual for a child to wake up with very smelly breath. Throughout the day, a child's saliva, swished around by the mouth muscles, washes away unwanted debris. As soon as a child falls asleep, saliva production plummets, and the muscles relax. The longer a child sleeps, the higher the bacterial count in the mouth rises, resulting in "morning breath." In children, smelly breath that persists throughout the day is most often the result of mouth breathing, which dries out the mouth and allows the bacteria to grow. Children who consistently breathe through their mouths might have colds, sinus infections, allergies, or enlarged tonsils or adenoids blocking the nasal passages, so a visit to the pediatrician is in order.