Skin Glands: Dogs do not produce sweat to cool off. However, dogs do have sweat glands, called apocrine glands, associated with each group of hairs. Apocrine glands likely produce pheromones, or chemical signals, for communication with other dogs.

Dogs also have another type of sweat glands, called eccrine glands, on the pads of their paws and on their noses, which help keep these areas moist and functioning properly. On the paw pads, natural micro-organisms live in the surface layers and contribute to the paw’s typical odor – like cheese puff snacks or Fritos! This odor is much more noticeable on dogs with moist paw pads than on those with dry pads.

Dogs also have numerous glands, called ceruminous glands and sebaceous glands, in their external ear canals. Together these two sets of glands produce natural ear wax, or cerumen. Micro-organisms live naturally in this material and give the ears a slightly yeasty odor even when ears may be healthy.

Dogs, like all carnivores, have two scent glands called anal sacs that communicate with the surface of the skin by ducts that open on either side of the anus. They produce a natural secretion that varies from thin and yellowish to pasty and grayish. Anal gland secretions may have a very strong musty odor. A small amount of this material is normally deposited when dogs defecate and a large amount may be extruded when a dog is frightened. This secretion is thought to leave a signal to other dogs telling them who left fecal deposit. This odor is also the signal being sampled when strange dogs investigate one another by sniffing out the anal area.

Another source of odor that can be considered natural results from a common dog behavior. Dogs like to roll in and mark themselves with animal products in their environment, including fecal deposits of natural prey animals. One of their favorites is rabbit droppings. This might be a method of communicating with pack members about the other animals that are active in the pack home territory, a behavior left over from ancestor wolves.

Un-natural Sources of Odor on Pet Dogs

Poor grooming: Some dogs, especially those with long, thick or corded hair, need regular grooming. A coat that is not kept clean and groomed can trap dirt and other substances with unpleasant odors. If a dog’s haircoat is chronically wet, it can harbor lots of bacteria and yeast. 

Skin diseases: Dogs with allergies (allergic dermatitis, atopic dermatitis) may have a musty odor. This is because allergies can cause increased sweating (hyperhidrosis), bacterial skin infections (bacterial dermatitis or pyoderma) and yeast skin infections (Malassezia dermatitis). Dogs with seborrhea, a type of keratinization defect, and dogs with deep skin folds are also prone to bacterial and yeast skin infections.

Ear diseases: Ear infections, or otitis are a common source of odor in dogs.  The smell can be yeasty or actually smell like sewage.

Anal sac diseases: Excessive anal gland secretion can result in a musty, pungent odor. Anal sacs can also become abscessed or infected, with bacteria or yeast organisms then producing an odor.

Dental disease: Various dental diseases can cause bad breath, or halitosis. Dental calculus harbors numerous bacteria that produce odor. Dental disease can also lead to excessive drooling, causing the skin around the mouth to become infected and odiferous.

Medications: Some medications, especially antibiotics or medicated shampoos, have odors that owners may find unpleasant. Chlorhexidine is a common disinfectant incorporated in skin medications that some people find has an unpleasant smell.

Diet: Some dog foods based on fish meal or with added fish oil can make for fishy-smelling dogs.

Flatulence: The overproduction of intestinal gas can be a problem for some dogs.  This may be diet-related or a sign of gastrointestinal disease. 

Skunks: Dogs and skunks don’t mix well and a dog may be sprayed in the encounter. This results in an over-powering musky acrid odor that remains apparent in the ‘skunked’ dog’s coat for many days or even weeks until steps are taken to neutralize the odor.