A.
Bad breath can be caused by postnasal drip from from allergies and I think either viruses or bacteria (sorry, I don't remember which). I don't know about an ammonia smell, but would you also describe it as a metallic smell? I've noticed that sometimes with my kids when sick (and even myself having that kind of taste in my mouth when sick). Good luck- like my sister always tells me, the simplest (least scary) answer is usually the right one, but that doesn't keep me from researching online, either!