Why Does My Cat Open Their Mouth After Sniffing?

A cat may slightly open their mouth after investigating a scent as part of the flehmen response. This behavior is associated with sampling scent chemicals through the vomeronasal organ, also called Jacobson’s organ. The expression can look like a small gape or grimace, but appearance alone cannot tell you whether an open mouth is harmless.

If your cat is breathing with their mouth open, panting, or having difficulty breathing, seek emergency veterinary care immediately. Do not assume it is flehmen because they sniffed something first. AAHA treats open-mouth breathing in cats as an emergency, and Cornell advises immediate veterinary care whenever comfortable breathing is in question.

What Is the Flehmen Response?

The Merck Veterinary Manual describes flehmen in feline scent communication. The cat may lift the head, slightly open the mouth, and change the position of the upper lip while investigating scent information.

VCA’s explanation of flehmen connects the response with the vomeronasal organ and the processing of chemical signals, including pheromones. Pheromones are chemical signals involved in communication between members of the same species.

You do not need to picture a cat consciously analyzing a smell as a person might. “Scent sampling” is a useful plain-language description of the behavior. It does not tell us exactly which information your cat obtains from any particular cushion, shoe, or spot on the floor.

Why Does It Look Like a Funny Face?

A partly open mouth and changed lip position can resemble a human expression, which is why people sometimes call flehmen a “stinky face.” That nickname is not evidence that your cat finds the smell disgusting. An interesting scent and an unpleasant scent are not the same thing, and we cannot translate the expression into a precise opinion.

Nor does a cat need to hiss, bare their teeth, or react dramatically for scent investigation to be interesting. Watch what your cat chooses to investigate without encouraging a bigger response. Cat Body Language: What Common Cat Signals Mean explains why context matters more than an isolated facial detail.

Is My Cat Tasting the Smell?

“Tasting the air” is sometimes used as a shorthand description, including comparisons between smelling and tasting in popular explanations. It is better to think of flehmen as scent-related chemical sampling than to assume the cat is tasting an object in the ordinary food sense.

The name of the organ is enough for this explanation; a household observation does not show how a particular chemical moved through it. It also cannot tell you that a cat has identified another animal’s exact age, health, or intentions.

For a separate question about food taste, see Can Cats Taste Sweet Things?. And when a cat brings their face close to an object, more than one sensory system may be involved: Why Do Cats Have Whiskers? covers touch information rather than scent sampling.

Do Not Use a Photograph or Timer to Rule Out Illness

A picture of a cat with a slightly open mouth cannot confirm flehmen or exclude a breathing problem. The same is true of a video caption calling it “normal.” Sniffing beforehand supplies context, but it is not a safety test.

• Do not decide that a mouth opening is safe because it is small.
• Do not wait for a set number of seconds or for another episode if breathing concerns you.
• Do not hold something near your cat’s face to try to reproduce the expression.
• Do not delay veterinary care while comparing your cat with online images or counting breaths.

The emergency action is about breathing, not the nickname given to a facial expression. Cornell notes that breathing difficulty has many possible causes and needs veterinary assessment; a home explanation of flehmen cannot determine the cause or treatment.

What Should You Do During Ordinary Scent Investigation?

There is no need to interrupt a comfortable cat simply to stop them making an unusual face. Let them investigate voluntarily and move away when they choose. Do not open their mouth, manipulate the lip, or introduce strong-smelling substances to produce a demonstration.

If you are worried about a new or unexplained mouth movement, ask your veterinary team about it. If the concern is whether your cat can breathe comfortably, seek emergency care immediately instead of waiting for a routine reply. AAHA’s respiratory-distress handout directs owners straight to emergency care; calling ahead should not become a reason to delay getting there.

Helpful Related Guides

• Cat Body Language: What Common Cat Signals Mean
• Can Cats Taste Sweet Things?
• Why Do Cats Have Whiskers?

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