I have a miniature schnauzer with breath that can clear a room. She is nearly 15 and the vet says too risky to clean/remove more teeth. She does not have many teeth as it is and we and the vet do not think they are causing her pain. However he gave her a course of antibiotics and the bad smell went. Now she has finished the course sadly it is returning. The same happened over a year ago. We think it might be an internal problem but before we return to the vet wonder if anyone has an opinion on what could be wrong. Seems odd that during course of antibiotics her breath becomes fine but within couple of days of meds complete it is again fetid. She does have a large lump on her side which has enlarged over the years, vets say nothing serious. She has become deaf and has limited sight and has had leichmanosis which was diagnosed at least 5 years ago but does not appear to have progressed. Any thoughts appreciated.