If your dog has seriously bad breath, you may think this is a normal thing. Considering some of the things your dog licks and eats, it's easy to assume they are going to have bad breath. However, very bad breath that is a constant thing in your dog usually means there is an underlying problem. If ignored, dental issues that are causing your dog's bad breath can spell big trouble. Your dog can be susceptible to a lot of the same types of dental issues that affect humans.