If your dog or cat rides along with you, it's a fair question — animals have much more sensitive noses and different chemical sensitivities than we do.
Cats are more sensitive than dogs
According to ASPCA Poison Control, cats have a reduced ability to metabolize certain compounds found in concentrated essential oils, and are more commonly affected through grooming (licking fur that's been in contact with a product) or direct skin contact than through simply smelling the air. Concentrated or 100%-strength essential oils and diffusers carry more risk than a low-level ambient scent. Dogs are generally less sensitive than cats to these compounds, though very strong odors can still be unpleasant or irritating to a dog's much more sensitive nose.
What this means practically
- Inhalation risk from a mild, hung air freshener is generally lower than risk from direct contact — so keep fresheners out of reach of a pet that might chew on or lick them, especially cats.
- If your pet seems agitated, sneezes repeatedly, or tries to avoid the area after you hang a new scent, take it out and let the car air out — that's a sign the concentration is too strong for them, even if it's fine for you.
- Skip essential-oil-based or very high-concentration products if you regularly travel with a cat.
A quick note on claims you'll see online
You may see specific statistics floating around (like "X thousand pet poisonings per year from air fresheners") — we couldn't verify a credible source for these numbers, so we're not going to repeat them here. The honest answer is: there isn't strong published data quantifying air-freshener-specific pet incidents. The ASPCA's general guidance on concentrated fragrance and cats is the most reliable thing to go on.
Bottom line: a mild-scented paper air freshener, kept out of chewing/licking reach, is a low-risk choice for most dogs. With cats, be more cautious, watch for signs of irritation, and avoid anything at high concentration.
Sources: ASPCA Poison Control, "Are Essential Oils Dangerous to Pets?" (aspcapro.org).