Most babies have sweet smelling breath, but occasionally baby bad breath does occur. It can be a particular problem upon waking, after the baby has been asleep for a few hours - like morning breath in adults. During sleep, the mouth is typically relaxed and motionless, there is decreased saliva production, and bacteria that live in the mouth cavity have an opportunity to multiply undisturbed. Some of these bacteria can produce the unpleasant odor we associate with bad breath, and when they multiply to sufficient numbers, the odor becomes detectable.
If you think that "morning breath" is causing bad breath in baby, try treating it by cleansing the mouth before putting baby down for a nap. If baby is very young and has no teeth, encourage a water rinse to flush traces of formula or bits of food out of cracks and crevices. If baby has teeth, a gentle brushing and a rinse should help. Rinsing and brushing upon waking can be helpful too. (Fluoridated toothpastes should be used very sparingly in young children, and brushing should always be supervised even when your child is old enough to begin brushing on her own.) If these measures relieve the baby bad breath, you needn't do more.
However, if bad breath in baby persists after brushing and cleansing, there may be another problem. Does baby use a soother or habitually suck on some other object like a blanket or stuffed toy? An object that is continually put into the mouth gets coated with saliva and oral bacteria and can develop an unpleasant odor. Though the smell may not be offensive to your child, it can contribute to lingering bad odors in the vicinity of baby, and to baby bad breath. The simple solution is to wash or replace the offending item regularly. Eventually, your child will give up the sucking habit and the problem will disappear on its own.
Occasionally bad breath in baby has a more sinister cause. If your efforts to solve the problem are fruitless, you should consult your pediatrician or family doctor. The physician will check for signs of throat or sinus infection, infection somewhere in the mouth, tooth decay, or a foreign object lodged in a nasal passage. Sinus congestion can contribute to baby bad breath as well, by causing baby to breathe through the mouth: dry mouth is a cause of breath odor in both children and adults because saliva is naturally antibacterial and, in a healthy mouth, it keeps the population of odor causing bacteria at a minimum.
Once again, baby bad breath is relatively unusual: if simple measures don't solve the problem, your child should be seen by a medical professional to rule out more serious problems.
R. Drysdale is a freelance writer with more than 25 years experience as a health care professional. She is a contributing editor to Bad Breath Cure, a blog dedicated to the treatment of bad breath.