Skin Disease
The skin is a natural barrier to infection; when it is compromised, infection, irritation and abnormal oil production are possible. There are several potential causes of skin disease in dogs.
Ear Infections
Ear infections often cause dogs to shake their heads and scratch their ears. Often, there is ear discharge or debris, and the ears can have a bad odor. Ear infections may be itchy or even painful. When left untreated, they can cause serious damage.
Internal Organ Disease
Some diseases that affect the internal organs of a dog can result in bad breath. Both kidney failure and diabetes can give your dog unusually bad breath
Anal Gland Issues
Anal glands are two small sacs in the wall of the rectum of dogs that contain foul-smelling liquid that is used in scent marking in the wild. Dogs will naturally express their glands if they are defecating or sometimes when scared
Gas
Dogs occasionally experience flatulence and, unfortunately, we have to smell it. But what causes this gas? Digestive upset from dietary changes like a new food or treat, eating something in the yard, medications, intestinal parasites
Dirty Water
If your dog has recently been swimming in dirty water, an unpleasant odor might linger even after your dog has dried. If this occurs, it's time for a shampoo!
Rolling in Something Stinky
Dogs love to roll around in smelly things, which results in a stinky dog. If your dog has been having a little too much fun outside in the yard, a simple bath should undo this damage.
Skunk Spray
This distinct smell only comes from one source. If your dog has been sprayed by a skunk it will need a special bath to get rid of the smell.
Dental Disease
Arthritis is defined as inflammation of a joint or multiple joints in the body. In dogs, the most common form of arthritis is osteoarthritis, also called Degenerative Joint Disease.