Glossary

Flehmen response

The open-mouthed grimace a cat makes when it draws a scent to a special organ in the roof of its mouth.

Also called: flehmen, flehmen grimace, gaping

The flehmen response is the face a cat pulls when it has met an interesting smell: the mouth opens slightly, the upper lip curls back, and the cat seems to stare into the distance for a few seconds. It looks like disgust, but the cat is doing the opposite and taking a closer look.

The cat is drawing air over the vomeronasal organ, a small scent organ in the roof of the mouth. This organ reads chemical messages such as the pheromones in another cat's urine or the scent a person has left on a sock. Tigers, horses and many other mammals do the same.

You will see it most often when a cat sniffs a spot where another animal has been, and in unneutered males that have found the scent of a female in season. Occasional flehmen is normal. If a cat grimaces often with drooling, bad breath or trouble eating, mention it to a vet, because mouth pain can look similar.

Last reviewed November 7, 2026

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Related terms

Vomeronasal organ A small scent-analysing organ in the roof of a cat's mouth that reads chemical signals such as pheromones. Scent marking How a cat leaves chemical messages on objects, people and places using glands in its face, paws and body, and in its urine. Pheromones Chemical signals that cats release from glands and in urine to communicate with other cats, sensed through the nose and a special organ.

Related guides

How cats see, hear and smell How a cat's eyes, ears and nose differ from ours, what this means for daily life at home, and which changes in the senses call for a vet.