They say that dogs can smell cancer on people, and apparently, it’s true. Preliminary studies have indicated that due to their keen olfactory abilities, they can pick up the scent of compounds generated by malignant tumors. But were you aware that people can smell a certain type of cancer on their dogs? Not just cancer but other diseases as well. Granted, a dog’s sense of smell is many, many times stronger than ours. But some of the odors a sick dog gives off are intense enough for our noses to detect. There are some other little known — but easy to detect — clues to dogs’ health as well. Here’s a rundown.
Diabetes. When a dog (or person) has diabetes mellitus, he is not able to efficiently break down sugar to use as fuel for the body and so begins breaking down fat. Ketone bodies are then produced and accumulate in the blood. A dog works to eliminate ketones through respiration, which give his breath a sweet odor that’s perceptible to people.
Dogs smell it on people, too. In fact, dogs have been trained to bark when their owners with type 1 diabetes start to experience hypoglycemia, a situation in which blood sugar falls too low, perhaps in response to medication’s overshooting the mark in combatting the disease. If left untreated, it can result in a diabetic coma. But the barking lets the person know he should ingest something sweet — perhaps a glass of juice — to raise his blood sugar.
Kidney disease. Dogs with kidney disease do not properly filter breakdown products of protein into the urine. As a result, those breakdown products build up in the blood. One of them is blood urea nitrogen. A dog with high levels of blood urea nitrogen resulting from compromised kidneys enables a person to smell ammonia on his pet’s breath. Ammonia, a breakdown product of urea, contains nitrogen.
Urinary tract infection. Some say it smells sour, while others equate it with the odor of rotting fish. However you describe it, a dog with a urinary tract infection may pass urine that has a very foul smell. Or at least a very unusual one. “The urine will suddenly take on a much stronger odor, or a much different odor, than it has in the past,” says Your Dog editor-in-chief John Berg, DVM. “If it doesn’t go away, take your pet to the veterinarian for a workup.” Once a urinary tract infection is diagnosed, an antibiotic will be prescribed and will clear up the infection — and the malodorous scent in your dog’s urine.
Dr. Berg points out that the absence of an odor doesn’t mean there’s not a urinary tract infection. Other signs of one are more frequent urination and straining to urinate — with or without the attendant change in scent.
Note: Prior to coming into heat, a female dog’s urine may become especially pungent to alert male dogs that she is near ready to impregnate. Incontinence in, say, an older dog will lead to an unpleasant odor, too, but for an entirely different reason. If the dog dribbles into his fur or skin while resting or sleeping, the urine will dry there — and the scent will remain.
Yeast infection. The odor of sickness coming from a dog’s ear can be especially unpleasant. A yeast infection, which is a type of fungal infection, can cause an odor that smells like fermentation. If you notice a brown, waxy discharge upon looking at your dog’s ear (just the part you can see by looking into the pinna, or flap — don’t go further in), a yeast infection may very well be the cause. It will perhaps be soupy in appearance.
A bacterial infection in a dog’s ear can also smell particularly pungent — or even somewhat sweet if the bacteria are of the relatively common pseudomonas variety. In bacterial cases, the discharge tends to present as a yellowish to green pus. To clear up the problem, the dog will need topical medication in addition to taking medication by mouth.
Note: Ear infections sometimes result from infestation by mites. The telltale sign is granular, dark brown material in your dog’s ears. Think: coffee grinds.
Parvovirus. Diarrhea has never had a reputation for smelling good, of course, but when a dog has parvovirus, his odor can be particularly foul. The smell comes from dead tissue. The virus mounts such an attack on the lining of the intestine that it causes intestinal cells to die. The dead cells slough off and make their way into a dog’s waste. “Dead tissue has a really nasty odor,” says Dr. Berg.
Parvovirus, often accompanied by lethargy and vomiting in addition to smelly (and often bloody) diarrhea, is an extremely serious, life-threatening disease if left untreated. Just about all pet dogs are inoculated against the condition, but if for some reason yours has missed his booster shot — or your puppy has missed one of his initial vaccinations — and he exhibits the characteristic symptoms of the illness, don’t delay in getting him to the doctor. Young dogs are more apt than others to develop the problem.
Oral tumors. Just as dogs can smell cancer on us, we can smell it on them — if it is in their mouths. The scent is literally sickening — hard to take in some instances. It comes from the necrosis [death] of cells. A change in the odor of a dog’s breath can also indicate a malignant tumor. “Don’t just chalk it up to doggie breath,” advises Dr. Berg. “Take your dog to the doctor, particularly because oral tumors are often in the back of the mouth, where they’re not really that noticeable.” Unfortunately, oral tumors can be among the most difficult to treat. They tend to grow fast, into surrounding bone and tissue, and they also spread quickly to other sites in the body. Such tumors are usually seen in large breeds.
Severe periodontal disease. With some dogs, it smells as if you’re staring into the mouth of a whale when you get too near them. They simply have awful breath. That in itself is not a problem — for the dog, anyway. But if the odor is particularly strong and foul, and especially if it’s in conjunction with loose teeth and pus, the dog probably has advanced periodontal disease, which is a fancy way of saying that the gums surrounding his teeth have deteriorated to a significant degree, and perhaps the bone around his teeth, too. Once the bone erodes, it can no longer anchor the teeth, which is why they loosen — and potentially fall out. If the problem remains unchecked, even the jaw can weaken to the point that small blood vessels beneath the bone become damaged and bleed, allowing a pathway for bacteria to enter the bloodstream. You can avoid this cascade of events by brushing your dog’s teeth once a day, every single day, and by taking him for dental cleanings when the veterinarian suggests them. Older dogs, in particular, may need a professional cleaning once or twice a year to remove “gunk” that has accumulated under the gum line, where you can’t reach.
Skinfold pyoderma. A pyoderma is a bacterial infection of the skin, and, not surprisingly, a skinfold pyoderma is a bacterial infection that takes hold in the folds of a dog’s skin. A fold, which allows two adjacent skin surfaces to touch each other or be very near each other, provides the perfect environment for bacteria to thrive: warm and humid. The bacteria are native to the skin, but when they overgrow in that moist environment, problems start. Along with discharge, there’s often a telltale foul, or musty, odor. Wrinkly breeds like shar peis and English bulldogs are particularly susceptible, but any dog could end up developing skinfold pyoderma in the folds of the lip, the groin, or the “arm” pits. Sometimes it develops in female dogs between the mammary glands if they have had multiple litters. A female dog might also develop the condition above her vulva if she has a congenital condition called a recessed vulva, which means there’s a skinfold right above the tissue on the external part of the vagina. Treatment includes using a medicated skin cleanser on the affected area along with antibiotics, and sometimes surgery. Owners need to keep susceptible areas clean and dry to prevent recurrence.
Keep in mind that for most of the conditions we’ve described, abnormal odors are a relatively insensitive indicator of a problem. The fact that your dog passes your sniff test does not mean you can skip regular veterinary visits!