People usually notice a cat’s sense of smell when something changes: a formerly keen eater turns away from food, a new diffuser makes them sneeze, or a household introduction goes strangely tense. For cats, scent is not background detail. It’s how a place feels familiar, how other animals are assessed, and how food is judged as worth eating.
Below is a clear look at how a cat’s olfactory system works, what that “odd face” (the flehmen response) is really doing, and when smell-related behaviour can hint at stress or illness. Along the way, a few common myths get trimmed back to size, especially the ones about exact receptor counts and “safe” home fragrances.1, 2
The anatomy of a cat’s nose (and the extra scent organ you can’t see)
What the nose is built to do
A cat’s nose is designed for fine sampling. Inside the nasal cavity, curled bony shelves (turbinates) create a large surface area where scent molecules meet the olfactory lining. It’s quiet, efficient engineering: more contact area, more information extracted from each breath.
Jacobson’s organ (the vomeronasal organ)
Cats also have an accessory scent system: the vomeronasal organ (often called Jacobson’s organ). It sits in the hard-to-notice space behind the upper front teeth and connects via ducts, helping the cat process pheromones and other chemical cues that carry social and reproductive information.2, 3
How strong is a cat’s sense of smell, really?
You’ll often see a precise number—“200 million receptors” and “14 times stronger than humans”. The reality is less tidy. Receptor estimates vary widely across sources, and receptor counts alone don’t perfectly predict real-world smelling ability. What’s stable is the big picture: cats generally smell far better than humans, and they use that advantage constantly—especially around food, territory, and other animals.1, 4
What cats use smell for in daily life
Mapping a place and deciding what’s safe
When a cat enters a room, the nose gets there first. Sniffing doorways, corners, bedding, and favourite pathways helps build an “olfactory map”: what’s familiar, what’s new, and what may have passed through recently. A home that smells predictable tends to feel safer.
Hunting and feeding
Smell supports hunting—especially tracking what’s nearby or recently present—even when the prey isn’t visible. At the food bowl, smell is part quality-control: cats often hesitate with unfamiliar diets, and they’re less interested in food they can’t smell properly.
Communication through scent (the messages left on furniture, humans, and other cats)
Territory and familiarity
When a cat rubs their face along chair legs, doorframes, or your shins, they’re transferring scent from facial glands. Scratching also leaves scent signals (as well as visible marks). These cues help set boundaries and maintain a familiar “house smell” that reduces uncertainty for the cat moving through it.
Why cats sometimes pull a strange face
The open-mouthed, lip-curled “grimace” is usually the flehmen response. It helps draw scent molecules towards the vomeronasal organ so the cat can analyse them more precisely—particularly pheromone-like signals in urine, faeces, or on fur. It can look theatrical, but it’s simply a sensory manoeuvre.2, 3
Smell, behaviour, and stress
Because scent carries so much meaning, strong or unfamiliar odours can unsettle some cats. Renovations, heavy cleaning products, new furniture, visitors with dogs on their clothing, or a new cat’s bedding can all shift the scent landscape quickly.
If you’re trying to keep things steady during change, it often helps to think in scent terms:
- Keep a few “safe-smell anchors” (familiar bedding, a well-used scratching post) in the same place.
- Avoid washing everything at once; rotate cleaning so the home doesn’t suddenly smell like nothing.
- When introducing animals, swap bedding gently and gradually so scent becomes familiar before face-to-face contact.
When smell changes can signal a health problem
Reduced smell can reduce appetite
In cats, appetite is tightly linked to smell. When nasal passages are congested—commonly with an upper respiratory infection—cats may struggle to detect food odours and eat less as a result. If a cat is off their food, congested, or drooling, the safest move is a veterinary check rather than assuming fussiness.5, 6
Common issues that interfere with smelling
Problems that can affect smelling (and therefore eating and behaviour) include:
- Upper respiratory infections causing sneezing and nasal congestion5, 6
- Dental disease and oral pain, which can change how a cat approaches food and scent cues5
- Nasal obstruction (for example, polyps or masses), especially if there’s persistent discharge or noisy breathing (needs veterinary assessment)
Using scent safely to enrich your cat’s environment
Good scent enrichment: mild, controllable, and cat-led
The safest enrichment smells are the ones cats can approach and leave freely. Catnip is a classic, and some cats respond to silver vine. Keep it occasional and localised (a toy, a scratcher), so the cat isn’t trapped in a strong smell throughout the house.
Be cautious with essential oils, candles, and diffusers
Many essential oils can irritate airways or be toxic to pets at high concentrations, and cats are considered particularly vulnerable. If you use scented products at all, keep rooms well ventilated, give the cat an easy way to leave the area, and never apply essential oils directly to your cat’s skin or coat (they can absorb it and ingest it during grooming). When in doubt, don’t use them.7, 8
Final thoughts
To live with a cat is to share a home with an animal that reads the world in molecules. When scent stays steady, cats often look calmer and behave more predictably. When it shifts—through illness, stress, or strong fragrances—the ripple can reach the food bowl, the hiding spots, and the relationships in the house.
Small choices help: keep familiar scent anchors, introduce change slowly, and treat appetite changes as information, not stubbornness. The nose is not just a feature on a cat’s face. It’s one of the main ways they understand where they are.
References
- VCA Animal Hospitals — Cat vs. dog: Sense of smell
- Encyclopaedia Britannica — Why do cats open their mouths after smelling something? (Flehmen response & Jacobson’s organ)
- PetMD — What is the flehmen response in cats?
- Merck Veterinary Manual (Consumer) — Senses of cats
- Cornell Feline Health Center — Respiratory infections (including appetite effects from nasal congestion)
- VCA Animal Hospitals — Feline upper respiratory infection
- RSPCA South Australia — Keeping your pet safe (note on scented candles/diffusers and essential oils)
- ABC News (Australia) — Essential oils and oil diffusers could be harming your pet
- Animal Emergency Center — Essential oils: Not essential for pets (toxicity information)
Veterinary Advisor, Veterinarian London Area, United Kingdom