Babies usually do not have bad breath, but sometimes their breath has an unpleasant, unhealthy smell. It's particularly alarming when a baby's breath smells like alcohol or acetone. This may be either the result of a serious condition, or something minor. The causes listed below are, of course, no substitute for professional medical advice; concerned parents should immediately consult their baby's physician.
Babies who breathe through their mouths or suck on their thumbs persistently may dry out their mouths, creating an environment that's favorable to bacteria growth. Bacteria will smell bad on its own, and may create some compounds with an alcoholic smell. Because bacteria in the mouth may develop into infections like a sinus infection, it's important to watch out for illness in babies with bad breath.
Breath that smells strongly of rubbing alcohol or acetone may be a symptom of diabetic ketoacidosis (DKA), which results from the body lacking the insulin to break down sugars and instead breaking down fatty compounds. This is obviously a serious condition. Babies suffering from DKA will appear very ill in other ways, with dehydration being very apparent.
Babies with alcoholic breath may have simply ingested alcohol, phenol or salicylate-based compounds. Because babies love to put things in their mouths and up their noses, it's understandable that accidental ingestion could occur, and parents of babies with odd breath should make sure that there are no telltale substances within the baby's reach.