May 15, 2026, 2:52 pm | Read time: 7 minutes
Anyone who smokes knows the phrase: Smoking can be deadly. Usually, people think of themselves or those in the same room. But there’s often someone else who can’t object, can’t ventilate, and can’t just leave: a dog, cat, bird, or rabbit. They sit in the smoke, later lie on contaminated blankets, or groom toxins from their fur. That’s why secondhand smoke is more than just an unpleasant smell for pets. Suddenly, the cigarette in the apartment is not just a personal choice but a deadly threat to beloved pets.
Is Secondhand Smoke Dangerous for Pets?
Yes, and not only when smoking directly next to the pet. Secondhand smoke consists of the smoke produced when a cigarette burns and the smoke exhaled by smokers. For pets, there’s an additional factor: so-called “thirdhand smoke.” This refers to residues that settle on surfaces after smoking–such as on furniture, carpets, clothing, skin, or in fur.1
This is what makes secondhand smoke so insidious for pets. Dogs and cats live close to the ground, lie on carpets, snuggle on blankets, and come into contact with contaminated surfaces. Cats additionally ingest toxins while grooming their fur with their tongues. Birds also groom their feathers and can absorb residues that way.
Nicotine Residues Can Be Detected in Dogs’ Bodies
How significantly secondhand smoke affects pets is shown in a study by Debora Groppetti and her team from the Università degli Studi di Milano in 2023. The researchers examined 32 clinically healthy dogs: 16 lived with smoking owners, and 16 in non-smoking households. The key question was not only whether smoking occurred but whether the exposure could also be detected in the animals’ bodies.
To do this, the researchers measured cotinine, a nicotine metabolite, in the dogs’ blood serum and fur. The result: Dogs from smoking households had higher cotinine levels in both blood and fur than dogs from non-smoking households. The study thus shows that dogs do not just perceive tobacco smoke–the exposure is measurably present in their bodies.
However, this study does not prove that every dog in a smoking household will become ill. It does show that tobacco smoke is not an abstract threat to dogs. Even if owners do not see the risk, the animal’s body may already bear traces of it.
Secondhand Smoke and Cancer: What Studies Show About Dogs and Cats
Particularly concerning are the indications of an increased cancer risk. A 2024 study examined 120 Scottish Terriers aged six years and older over three years. This breed already has a particularly high risk of bladder cancer. The results are therefore not easily transferable to all dogs. Nonetheless, the study is important because it found a specific link between cigarette smoke and bladder cancer in this risk group.
In 32 of the 120 dogs, bladder carcinoma was confirmed. The analysis showed: Scottish Terriers living in households with cigarette smoke had about six times the risk of developing this form of cancer. Additionally, 35.3 percent of dogs with measurable cotinine levels in their urine developed bladder carcinoma.
There are also indications of an increased cancer risk in cats. A study showed: Cats living in a smoking household were more likely to develop malignant lymphomas, or cancer of the lymphatic system. If a cat was exposed to tobacco smoke, the risk was about twice as high. If it lived in a smoking household for five years or more, the risk was even about three times higher.2
Why Cats Are Particularly at Risk
Cats are very clean, and this can be their downfall in smoking households. If smoke particles settle in their fur, they are ingested during grooming with the tongue. This way, the toxins not only enter the respiratory tract but also directly reach the mucous membranes in the mouth and throat.3
Tobacco smoke can lead to respiratory problems, asthma, lung cancer, lymphomas, and tumors in the mouth area in cats. Indoor cats can be particularly at risk because they are constantly exposed to the toxins. They cannot avoid, ventilate, or decide to sleep in another room. This makes the difference from adult humans so crucial: Pets bear the risk without having a choice.
Birds and Small Pets Can Also Be Affected
The data is best for dogs and cats. But secondhand smoke can also lead to health problems in other pets. Birds are considered particularly sensitive to airborne toxins. Their respiratory system is very efficient. This is vital for flight but can become a problem with smoke exposure. Birds from households with tobacco smoke also showed significantly higher cotinine levels in their plasma than birds from non-smoking households.4
Possible consequences of smoke exposure in birds include respiratory irritation, conjunctivitis, skin problems, respiratory diseases, and in severe cases, life-threatening illnesses.
Rabbits, guinea pigs, and other small pets can also be affected by smoke. There are fewer specific studies for many of these species. Small animals have little body mass and sensitive airways. Therefore, even a small amount of toxins can affect them more than larger animals.
Cigarette Butts Can Be an Emergency
Secondhand smoke is not the only danger for pets. It becomes acutely dangerous when animals ingest nicotine directly–such as through cigarettes, cigarette butts, nicotine gum, nicotine patches, snuff, or e-cigarette liquids. Dogs can pick up butts during walks, and cats or birds can nibble on products left out in the open.
Nicotine is a neurotoxin. After ingestion, symptoms such as restlessness, tremors, muscle twitching, seizures, excessive salivation, vomiting, diarrhea, frequent urination, rapid breathing, or tearing can occur in dogs and cats within a short time. In severe cases, it can even lead to paralysis, circulatory shock, and death. Small animals, young animals, and birds are particularly at risk. According to the German Animal Welfare Association, even the oral ingestion of a cigarette butt can be fatal for pet birds.
If you suspect that an animal has ingested a cigarette, butt, or nicotine product, do not wait but immediately contact a veterinary practice or emergency veterinary service.
Bizarre Behavior! Blue Tits Use Cigarette Butts for Nest Building
These Household Chemicals Promote Cancer in Dogs
Not Just Cigarettes: Cannabis, Hookahs, and E-Cigarettes Are Also Risky
When it comes to smoking, it’s not just about traditional cigarettes. Cigars, pipes, or hookahs also produce smoke that pets can inhale. E-cigarettes contain fewer combustion substances than tobacco smoke but can release nicotine and other irritating or toxic substances. Liquids are especially dangerous if animals lick or swallow them.
Cannabis can also be problematic for pets. Dogs can develop symptoms such as drooling, restlessness, unsteady gait, gastrointestinal issues, and circulatory problems from cannabis smoke or THC-containing foods. In severe cases, the animal can even fall into a coma.
In cats, behavioral changes can occur. It’s important: If an animal may have ingested cannabis, owners should openly disclose this at the veterinary practice. Only then can proper treatment be administered quickly.
How to Protect Pets from Secondhand Smoke
The best protection is a completely smoke-free home and car. Enclosed spaces, in particular, retain smoke particles for a long time. Ventilation is better than nothing but does not reliably remove all residues from furniture, textiles, carpets, clothing, or fur.
If you can’t or don’t want to quit, you should smoke outside consistently, not directly at doors or windows where the smoke can drift back inside. Before petting, feeding, or picking up animals, washing hands is mandatory. Blankets, baskets, toys, and bowls must be cleaned regularly. Ashtrays, cigarette butts, tobacco, nicotine replacement products, e-liquids, and THC-containing foods should always be stored out of reach of animals.
In the end, the message is simple but uncomfortable: Pets do not smoke voluntarily. If smoking occurs near them, they bear a risk they neither understand nor can avoid. Quitting smoking not only protects your own health but can also, in the worst case, save the life of a beloved pet.