Air Fresheners, Candles, Incense & Oils: The Deadliest Toxins in Your Home, Part 1
Do You Know What’s in the Air Your Pet Is Breathing?
Most folks think about their pets’ health in terms of food, exercise, preventive care, and regular veterinary visits. But unless you’re a bird owner, you might not consider the quality of air your pets breathe inside your home.
Until recently, much of what we knew about indoor air quality came from human medicine or laboratory studies. But new veterinary research is beginning to fill that gap.
Scientists are now measuring the chemicals pets are exposed to inside ordinary homes and finding evidence that many common household products contribute to long-term disease.
This article looks at what that research has found, where those exposures come from, and the changes most likely to reduce them.
What Are VOCs and Particulate Matter?
Volatile organic compounds, or VOCs, are chemicals released as gases from certain solids and liquids. Sources include cleaners, fragrances, paint, adhesives, flooring, furniture, smoke and fuel.
Particulate matter, or PM, is different. It is a mixture of solid particles and liquid droplets suspended in the air. These particles may include dust, soot, smoke and other chemicals. They are classified by size:
- PM2.5: Fine inhalable particles measuring 2.5 micrometers or smaller. Wildfire smoke, tobacco smoke, incense, vehicle exhaust and cooking can produce PM2.5. These particles can travel deep into the lungs.
- PM10: Inhalable particles measuring 10 micrometers or smaller. Sources can include dust, smoke, construction activity, unpaved roads and other disturbed materials.
- Combustion gases: Carbon monoxide and nitrogen dioxide produced by fires, gas appliances, vehicles and other burning materials.
- Ground-level ozone: A reactive gas formed outdoors when other pollutants react in sunlight. It can irritate the lungs and worsen respiratory conditions.
Pets can be exposed more heavily because they spend more time indoors, rest close to floors where some pollutants settle and groom residue from their coats and paws.
What New Research Shows About Toxin Exposure in Homes
A 2026 study published in Frontiers in Veterinary Science measured urinary metabolites of volatile organic compounds (VOCs) in golden retrievers with lymphoma against healthy dogs.
- Two out of three dogs with lymphoma showed benzene exposure at DNA-damaging levels
- 9 in 10 showed xylene exposure
Here’s the key finding: over half of the healthy dogs had similar benzene exposure, and nearly all of them showed xylene exposure, too.
What’s so scary, though, is that these aren’t rare industrial exposures. This data reflects what pets are exposed to every day in a normal residential home.
An earlier 2025 study from the same lab found signs of DNA damage in dogs before they were diagnosed with lymphoma. Dogs with more exposure to VOCs and herbicides also tended to have more DNA damage.
Another 2025 study found higher signs of benzene exposure in boxers with lymphoma than in boxers without it. The results were similar for dogs living in cities and rural areas.
The physiology of common pets makes a crucial difference in their exposure to toxins versus a human’s exposure:
- Dogs breathe faster than we do and live closer to the floor, where heavier VOCs settle.
- Cats have shorter nasal passages that filter less, and they groom airborne particles off their fur, so they ingest what they inhale.
- Birds are a category of their own: their unidirectional respiratory system is extremely efficient at gas exchange, which means it’s especially efficient at absorbing toxins.
Air Fresheners, Plug-Ins, and Aerosol Sprays
These are the largest category of concern because these products passively emit deadly toxins 24 hours a day.
Plug-in, gel, and oil “air fresheners” don’t cycle on and off. They emit VOCs constantly, even when nobody is home.
Research at the University of Melbourne tested commonly used fragranced products and found that each emitted an average of 17 VOCs:
- 44% of those products released at least one carcinogenic hazardous air pollutant, including formaldehyde, acetaldehyde, methylene chloride, and 1,4-dioxane.
- Of 133 distinct VOCs detected across all products tested, only ethanol appeared on any product label.
Here’s where manufacturers get away with murder:
The word “fragrance” on a label is a trade-secret loophole. It can represent dozens of undisclosed chemical compounds, and manufacturers are not required to list them.
Specific chemicals documented in these products include:
- formaldehyde (a known carcinogen and respiratory irritant)
- naphthalene (linked to lung tissue damage in animal studies)
- 1,4-dichlorobenzene (linked to impaired lung function), and
- phthalates (endocrine disruptors)
What that means for your pet is that the vanilla plug-in running in the hallway or the little oil-based air freshener on the bookshelf is releasing a mix of deadly compounds you have no way to identify, directly into the air your animal breathes all day.
And aerosol sprays and air fresheners like Febreze, Glade, and Mrs. Meyers Clean Day products are a particularly nasty problem, because they deliver fragrance directly into the breathing zone of any animal at floor level.
Products You Might Not Think of as Air Fresheners
Many of these don’t look like air fresheners, which is part of the problem. They sit on shelves, clip to vents, line drawers, and go into litter boxes without registering as a source of continuous chemical exposure.
All of these release VOCs, synthetic fragrance compounds, or both into the air your pets breathe:
- Plug-in liquid or oil diffusers (Glade, Air Wick, Febreze)
- Reed diffusers
- Gel cone air fresheners (Renuzit and similar)
- Wax melts and wax warmers
- Hanging cardboard air fresheners
- Scented gel bead or pearl jars
- Clip-on or adhesive pod fresheners (Febreze Small Spaces and similar)
- Car vent clips and under-seat disc fresheners
- Aerosol air freshener sprays
- Fabric sprays (Febreze Fabric, Lysol Fabric Mist)
- Carpet and litter box deodorizer powders (Glade, Arm & Hammer)
- Scented trash bags
- Scented dryer sheets and fabric softener
- Potpourri, both dried and simmering
- Toilet rim clips and drop-in freshener tabs
- Scented drawer and closet sachets
- HVAC register vent clips
- Scented cat litter and litter fragrance additives
That last one deserves a closer look. Cats dig in their litter box with their face inches from the surface.
Scented litter and fragrance crystals put VOCs and synthetic fragrance compounds directly into a cat’s breathing zone during one of their most frequent daily activities.
Unscented, low-dust litter and a clean box do the job without adding to the load.
Scented Candles, Wax Melts, and Incense
Combustion plus fragrance = double exposure. Petroleum-derived paraffin-based candles release three to five times more VOCs than soy, beeswax, or coconut alternatives.
Even unscented combustion generates fine particulate matter (PM2.5) and the particles are small enough to reach deep into your pet’s lungs.
A Purdue University study documented nanoparticle formation when fragrance terpenes like limonene, linalool, and pinene (common in scented candles and wax melts) react with indoor ozone.
The result is the formation of secondary pollutants, including formaldehyde and reactive aldehydes (both respiratory irritants and potential carcinogens).
Incense deserves a separate mention because the particulate load is staggering:
- According to the American Lung Association, burning one gram of incense produces approximately 45 milligrams of particulate matter, roughly four times what a cigarette generates.
- A 2024 study published in Environmental Science & Technology confirmed that incense particle emissions are chemically similar to biomass burning aerosol, and that semi-volatile organic compounds in residential indoor air transfer easily to incense-generated PM2.5.
- The combustion products include polycyclic aromatic hydrocarbons (PAHs), carbon monoxide, nitrogen oxide, sulfur dioxide, and formaldehyde.
For birds, exposure to scented combustion can be fatal. For cats and dogs, the issue is a chronic, low-grade load.
And any pet recovering from a respiratory illness (kennel cough, feline asthma etc) isn’t able to filter additional irritants, making their illnesses difficult to resolve.
Essential Oil Diffusers
This category of toxins catches people off guard because marketing positions these products as “natural” and “safe.” But for cats, reptiles, and birds in particular, essential oils can be deadly.
Cats
Cats lack glucuronyl transferase, the liver enzyme that metabolizes phenolic compounds.
That makes them physiologically unable to process many popular essential oils, including tea tree, pennyroyal, citrus, pine, ylang ylang, peppermint, cinnamon, clove, eucalyptus, and wintergreen.
The Merck Veterinary Manual classifies these oils as toxic to cats and notes that active diffusers (both ultrasonic and nebulizing types) are even worse than passive ones.
Active diffusers aerosolize microdroplets that land on fur and are ingested during grooming, creating both an inhalation and an oral exposure.
Documented clinical effects range from vomiting, drooling, and ataxia to liver failure, seizures, and death.
Birds
Birds are especially vulnerable because their highly efficient respiratory systems are very sensitive to fragrances and aerosolized particles. Active diffusers can also leave oil droplets on feathers, which birds may swallow while preening.
Reptiles
Do not assume reptiles are safe simply because they process airborne chemicals differently from birds and mammals. Species-specific research is limited, and diffused oils can be inhaled or settle on skin, food, water, and enclosure surfaces, so use them only with guidance from an experienced reptile veterinarian.
“Pet-safe” essential oil products are not regulated for that claim, and the labeling is unreliable.
Next Steps
You may have chosen many common household products before you knew they could pose risks to animals. Take a room-by-room look at the fragrances, diffusers, candles, and air-quality products used in your home.
Replace higher-risk items as they run out, improve ventilation and filtration where possible, and ask your veterinarian about products that may affect your pet’s species or health conditions.
A few informed updates can make the air safer for every animal in the household, and for the humans who live with them.
About the Author
Brea Corwin is the founder of Bat Country Pet Sitting, providing professional in-home care for dogs, cats, parrots, reptiles, small mammals, and other companion animals throughout NW Portland, St. Johns, and University Park.
She holds an Honors BA in English from the University of Minnesota and is also a Certified Small Animal Massage Practitioner (CSAMP) with veterinary technician training in emergency and critical care.
Brea brings clinical experience to her work as a veterinary liaison and enrichment specialist for complex-care and multi-species households.
She is also a freelance SEO/GEO strategist, grant writer, and web content writer and strategist supporting nonprofits and small businesses in Portland and the Pacific Northwest. Read more about her experience on LinkedIn.
Resources
Genotoxic Herbicide Exposures in Golden Retrievers With and Without Multicentric Lymphoma
Environmental Chemical Exposures in Boxer Dogs With Multicentric Lymphoma
Environmental Chemicals and Lymphoma Risk in Dogs
Toxicoses From Essential Oils in Animals
Fragranced Consumer Products: Chemicals Emitted, Ingredients Unlisted
Pet Poisons: Be Mindful of These Household Products and Cleaning Agents
How Air Scenting Products Can Harm Your Pet