The Flehmen Response in Cats: Why They Make That Funny Face at New Smells

If you've ever watched your cat sniff something interesting and then freeze with their mouth slightly open, lips curled back, and a slightly dazed expression — you've witnessed the flehmen response. It looks almost comical, like your cat just smelled something they weren't quite ready for, but it's actually one of the more fascinating pieces of feline anatomy at work.

What Is the Flehmen Response, Exactly?

The flehmen response is a brief facial expression cats (and many other mammals, including dogs, horses, and big cats) make when they encounter a particularly interesting scent. The open-mouthed grimace helps pull air across the vomeronasal organ, sometimes called Jacobson's organ, which sits in the roof of the mouth behind the front teeth. This organ reads chemical information, especially pheromones, that a cat's regular sense of smell can't fully process. If you've noticed your cat's behavior shifting after a new scent shows up in the house, our My Pet Journal is a handy place to jot down when and where it happens, so patterns become easier to spot over time.

Why Cats Make That Funny Face

Cats reach for the flehmen response most often when they're investigating scent marks left by other animals — a whiff of urine on a windowsill, another cat's bedding, or even a visitor's shoes fresh from a walk outside. It's also common around unfamiliar people, new furniture, or a spot where another pet has been lounging. Rather than a sign of distress, the open-mouthed pause is a cat's way of gathering extra detail: is this scent familiar, is it a rival, is it a potential mate, is it worth marking over. It typically lasts only a few seconds before your cat shakes it off and moves on with their day.

Catnip, Curiosity, and the Flehmen Connection

Scent-driven curiosity is exactly why catnip is such a reliable enrichment tool. When a cat first noses into catnip, you'll often see sniffing, head-tilting, and occasionally a light flehmen grimace before the more familiar rolling-and-rubbing response kicks in fully. Our Organic Catnip pouch is a gentle way to give an indoor cat a fresh, safe scent to investigate, which is especially useful if your cat doesn't have much outdoor access to new smells on their own.

When the Flehmen Response Might Signal Something More

In the vast majority of cases, the flehmen response is completely normal and doesn't need any follow-up — it's simply your cat's nose (and palate) doing their job. It's worth paying closer attention, though, if the open-mouthed posture starts happening constantly, or if it shows up alongside drooling, pawing at the mouth, nasal discharge, or labored breathing, since those combinations can point to a dental issue, a respiratory irritation, or an oral injury rather than ordinary scent investigation.

A flehmen face on its own is nothing to worry about, but if it's paired with excessive drooling or your cat seems reluctant to eat afterward, it's worth a quick look from your vet to rule out something going on with the teeth or gums.

Bringing More Scent-Based Enrichment Into Your Cat's Day

Cats experience so much of their world through scent, and the flehmen response is a small window into just how much information they're pulling from a single sniff. Rotating in fresh smells — a new toy, a sprinkle of catnip, a cardboard box from a different room — gives your cat's remarkable nose something worthwhile to investigate, and that funny scrunched-up face is simply proof that it's working exactly as it should.

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Paris Deesing holds a degree in Biological Anthropology from UCLA and provides the editorial review behind each article, drawing on a long-held curiosity about the animals who share our lives.

This article was created using artificial intelligence with human editorial review and oversight.