Infection Ear infections can produce a nasty smell around your dog's ears. Your vet can diagnose an ear infection and prescribe medication to clear it up.
Breed Certain breeds, such as basset hounds, spaniels and bloodhounds, are prone to having smelly ears. This is because their droopy ears do not get as much air circulating around them as shorter-eared dogs.
Rolling Dogs love to roll in smelly things like dead birds or cat feces. If your dog's ears smell bad, it's possible it has rolled in something unsavory and needs to be bathed.
Dried Food Dogs with long ears often drag their ears on food and water bowls or along the ground as they walk. This can lead to food and dirt becoming stuck to the dog's ears, which can start to smell if not cleaned off immediately.