Cat Purring With Its Mouth Open: Flehmen or a Breathing Concern?

If your cat is purring with its mouth open, the safest next step is not to decide what the face means from a single moment or a video. In a scent-investigation context, a partly open-mouth upper-lip curl can be flehmen, a scent-related gape response. But flehmen is not an at-home all-clear. If the cat seems to be working to breathe or is breathing with its mouth open, seek urgent veterinary direction instead of trying to clear the episode as behavior.

What Flehmen Can Explain—and What It Cannot

Flehmen is a possible scent context, not a diagnosis. Merck Veterinary Manual describes the response as a gape expression or lip curl associated with interesting smells and the vomeronasal organ. A 1987 study by Hart and Leedy reported that flehmen in its tested cats was virtually always preceded by contact with scent material. Bradshaw’s 2018 review also describes the importance of feline olfactory and vomeronasal senses while emphasizing how difficult those signals are for people to interpret.

Those sources support a modest conclusion: after investigating an odor, a cat’s partly open mouth and raised upper lip can fit a scent-related response. They do not show that every similar-looking expression is flehmen, that the cat is healthy, or that a caregiver can identify the behavior reliably from a brief observation. They also do not establish that the cat is disgusted, judging someone, calm, sexually motivated, or recognizing a particular animal or person.

The distinction matters because “my cat is purring with its mouth open” can describe two different reader concerns: a curious face after a smell, or an apparent breathing change. The expression alone cannot settle which one you are seeing.

A Purr Does Not Clear an Open Mouth

Purring adds context, but it does not answer a health question. A 2009 Current Biology study found that some cats can use a purr with a cry-like component while soliciting food. Human listeners heard those tested solicitation purrs as more urgent than non-solicitation purrs. That is a specific finding about tested purr contexts, not a universal purr dictionary.

Use the same restraint here. A purr does not prove comfort, pain, hunger, or safety, and it cannot turn apparent open-mouth breathing into an ordinary behavior question. The guide to why cats purr explains why the sound belongs beside the situation and the rest of the cat rather than being translated on its own.

Make the Immediate Decision About Breathing

If your cat appears to be working to breathe, cannot breathe comfortably, or is breathing with its mouth open, treat that as an urgent veterinary question. Cornell Feline Health Center describes breathing difficulty as a clinical sign with many possible causes and advises veterinary care whenever there is a question about comfortable breathing. Merck identifies breathing difficulty and open-mouth breathing among serious emergency concerns, and Cats Protection also lists open-mouth breathing or marked effort as a reason for emergency advice or treatment.

Do not let a suspected scent trigger, purring, quietness between episodes, or a short duration reassure you that waiting is safe. The evidence does not provide a household visual test that separates flehmen from panting, dyspnea, airway disease, pain, fear, heat illness, poisoning, or another problem. A 2025 Veterinary Sciences study of 258 cats with severe emergency dyspnea found that the clinical presentation did not identify a particular cause before diagnostic workup. That referred emergency population cannot predict the cause or outcome for another cat, but it reinforces the boundary: visible breathing change is a clue, not a label.

If you call, use plain language rather than trying to choose the cause: “My cat appears to be breathing with its mouth open,” or “My cat seems to be working to breathe.” The cat panting guide covers the same urgent boundary in more detail. You do not need to prove that the episode was flehmen before asking what to do.

Do Not Turn Flehmen Into a Home Test

The source evidence does not authorize an intervention or a waiting routine. In particular:

• Do not offer urine, a stronger scent, pheromones, catnip, or another stimulus to see whether the expression happens again.
• Do not count breaths, compare videos, wait for a repeat episode, or complete a symptom checklist before contacting a veterinarian about apparent breathing difficulty.
• Do not inspect the mouth, pull the tongue, or try to sort the cause by looking more closely.
• Do not give food, water, medication, oxygen, steam, or a home remedy while trying to decide whether the expression is flehmen.

These are not missing steps in a better home diagnosis. The reviewed sources do not validate a caregiver’s ability to classify the episode that way, and delay is the main risk the boundary is meant to prevent.

Put the Boundary in Your New-Cat Plan

New owners can prepare one useful next step before a confusing episode happens: keep the veterinary clinic’s number available and know which emergency service your clinic uses after hours. If you need to call, describe the observable change and when you noticed it. Let the veterinary team decide whether the cat needs immediate assessment; do not use an online label, a scent trigger, or a normal-looking minute as clearance.

For a new kitten, the first-visit checklist can help you establish a routine veterinary relationship. It does not replace urgent care for breathing trouble. The practical rule is simple: flehmen may explain a scent-related lip curl, but it cannot clear a cat that appears unable to breathe comfortably.

The Takeaway

A cat purring with its mouth open may be showing flehmen after scent investigation. That possibility is useful context, not a conclusion about health. If the cat seems to be breathing with an open mouth or working to breathe, seek urgent veterinary direction rather than waiting to decide whether the expression has a behavioral name.