Bad breath (halitosis) is an all-too common problem in dogs and cats and can have a number of underlying causes. Certainly the #1 cause is periodontal (tooth and gum) disease. However, there are other things that can contribute to it as well, some more serious, some not so serious. These can include:
A “rotten meat” or necrotic smell coming from the mouth usually indicates the presence of a foreign body, tumor, or gum ulcers. An ammonia (urine) smell can result from both liver and kidney disease. A sweet, fruity mouth odor is often a consequence of unregulated diabetes.
If your pet's breath is exceptionally bad, have it checked out by your vet. If it turns out to be nothing serious, here are some measures you can adopt to help “sweeten” the deal: