A mothball smell on your dog usually points to one of two things: your dog came into direct contact with mothballs (or ate one), or an internal health issue is producing an unusual chemical odor through the skin or breath. The distinction matters because mothball ingestion is a veterinary emergency, while other causes range from manageable skin conditions to early signs of organ disease.
Your Dog May Have Found Actual Mothballs
The most straightforward explanation is the most urgent one. Dogs are attracted to mothballs because they’re small, roll around like toys, and some varieties have a slightly sweet scent. If your dog chewed on, licked, or swallowed a mothball, the chemical smell can linger on their fur, mouth, and breath for hours.
Mothballs contain either naphthalene or paradichlorobenzene, both toxic to dogs. Naphthalene is the more dangerous of the two. The toxic dose for a 22-pound dog is just one and a half mothballs containing naphthalene. Even partial ingestion can cause serious harm. Early signs include vomiting, diarrhea, abdominal pain, and lethargy. As poisoning progresses, it can damage red blood cells (causing a condition where the blood can’t carry oxygen properly), trigger seizures, and harm the liver and kidneys. Chronic exposure, even from fumes in a poorly ventilated closet, can cause cataracts over time.
If you suspect your dog ate or chewed a mothball, check the packaging to identify the active ingredient and contact your vet or an animal poison control hotline immediately. Don’t wait for symptoms to appear. Time matters with naphthalene poisoning.
Kidney Problems Can Produce Chemical Odors
When a dog’s kidneys aren’t filtering waste properly, toxins build up in the bloodstream. This creates a condition called uremia, which produces an ammonia-like or chemical smell on the breath. Some owners describe this as metallic, while others compare it to mothballs or cleaning products. The smell comes from waste compounds that the kidneys would normally remove but are instead circulating through the body and being exhaled.
Kidney disease in dogs develops gradually, and the breath odor often appears alongside other signs: drinking more water than usual, urinating more frequently, loss of appetite, vomiting, mouth ulcers, weakness, and weight loss. If the mothball smell is strongest on your dog’s breath rather than their coat, kidney function is worth investigating. A simple blood panel can check for elevated waste products that signal kidney trouble.
Skin and Ear Infections
Bacterial and yeast infections on a dog’s skin produce a range of strong, unpleasant odors. Yeast overgrowth (caused by a fungus that naturally lives on dog skin) is known for creating a musty, sour, or sometimes sharp chemical smell that intensifies in warm, moist areas like skin folds, ears, and paws. Some owners interpret this smell as mothball-like, especially when it’s concentrated in one area.
Yeast infections cause intense itching, so you’ll typically see your dog scratching, licking, or rubbing the affected areas. The skin may look red, greasy, or thickened, and the ears might have dark, waxy discharge. Bacterial infections can layer on top, adding their own odors to the mix. Both conditions are treatable but tend to recur if the underlying cause (allergies, moisture, immune issues) isn’t addressed.
Metabolic and Liver Conditions
The liver processes toxins and waste products from the blood. When it’s not working properly, those compounds can produce unusual body odors that seep through the skin and breath. Liver disease in dogs sometimes creates a distinctly chemical or sweet-chemical smell that doesn’t match the typical “dirty dog” odor owners are used to.
Signs that point toward a liver issue include yellowing of the gums, whites of the eyes, or inner ear flaps (jaundice), dark urine, vomiting, diarrhea, and a swollen belly from fluid buildup. Dogs with liver problems often lose interest in food and become unusually tired. These symptoms develop at different speeds depending on whether the liver damage is acute (sudden, from a toxin or infection) or chronic (building over weeks to months).
Environmental Contact
Sometimes the answer is simpler than a health condition. Dogs that explore closets, storage areas, attics, garages, or crawl spaces can pick up mothball residue on their fur without actually eating anything. Naphthalene is volatile, meaning it releases fumes as the solid slowly turns to gas. A dog that napped near stored mothballs or rolled around in a space where mothballs were used can absorb enough of that chemical scent to smell noticeably like them.
Check your home and any areas your dog has access to. Old mothball residue can linger in closets, storage bins, and under furniture for months or even years after the mothballs themselves are gone. If you find a source, ventilate the area and wash your dog thoroughly. Even fume exposure over time is worth minimizing, since prolonged inhalation of naphthalene can irritate the airways and, in rare cases, affect red blood cells.
How to Narrow Down the Cause
Start by locating where the smell is coming from. Sniff your dog’s breath, ears, skin folds, and coat separately. A chemical smell concentrated on the breath points toward something internal: kidney disease, liver problems, or recent ingestion of a toxic substance. A smell concentrated on the coat or in specific body areas is more likely environmental contact or a skin infection.
Next, look at your dog’s behavior. A dog that ate a mothball will typically show gastrointestinal distress (vomiting, drooling, refusing food) within hours. A dog with a yeast infection will be scratching and licking obsessively. A dog with organ disease will show broader changes: less energy, changes in appetite, increased thirst, or weight loss that developed over days to weeks.
If the smell appeared suddenly and your dog seems unwell, treat it as urgent. Naphthalene poisoning can escalate quickly, and kidney or liver crises need prompt treatment. If the smell is mild, your dog is acting normally, and you can trace it to a storage area or closet, a good bath and removing the source may be all that’s needed.