What Is the Flehmen or Flehmen Response in Cats?

How Cats Sniff Pheromones

The "Stink Face"
Cats look like they are snarling when they trap pheromones with their tongue. Erin Murphy/Flickr

Does your cat flehmen--sometimes make a weird sneering face? Cats lift their lips after a particularly long sniff and hold the mouth slightly open to sniff cat pheromones. Flehmen--a German word that means "lip curl"--might be mistaken for an aggressive snarl but is a perfectly normal and peaceful cat behavior.

How Cats Sniff Pheromones

Cats have a second scenting mechanism called Jacobson's organs, or vomeronasal organs.

These are found between the hard palate of the mouth and the septum of the nose. Jacobson's organs link to the hypothalamus in the brain that serves as sort of a switchboard to direct information to other areas. Tiny ducts connect them to openings behind kitty's teeth in the roof of the mouth.

Other Creatures That Have Jacobson's Organs

Cats are not the only critters with Jacobson's Organs. Strangely enough, even humans have them. They are named after a  Danish physician. According to Dr. Anne Marie Helmenstein "In the 1800s, Danish physician L. Jacobson detected structures in a patient's nose that became termed 'Jacobson's organ.'"  

According to Dr. Helmenstein, "While humans don't display the Flehmen reaction, recent studies have demonstrated that Jacobson's organ functions as in other mammals to detect pheromones and to sample low concentrations of certain non-human chemicals in ​air. There are indications that Jacobson's organ may be stimulated in pregnant women, perhaps partially accounting for an improved sense of smell during pregnancy and possibly implicated in morning sickness.

Since extra-sensory perception or ESP is awareness of the world beyond the senses, it would be inappropriate to term this Sixth Sense 'extrasensory'. After all, the vomeronasal organ connects to the amygdala of the brain and relays information about the surroundings in essentially the same manner as any other sense. Like ESP, however, the sixth sense remains somewhat elusive and hard to describe."

Probably the most well-known animal with a Jacobson's organ other than cats is the common snake, which, of course, is a reptile, not an animal. 

Kitty Sneer Caused By Flehmen Response

Cats flehmen (grimace) when their tongue traps pheromones, then flick-transfers to the duct in the roof of their mouth.

Pheromones are chemicals unique to a particular critter. For instances, cheek pheromones rubbed against objects can tell other cats that they are friendly or that the territory is owned. Pheromones in urine notify other cats if the cat is intact or fixed and whether a boy or a girl.

All cats use this second sniff-mechanism to analyze pheromones but male cats show the flehmen kitty sneer most often. That may be because they are particularly attuned to checking out sex-related information even if they are neutered. 

Cat's will also mark their favorite humans with pheromones as well. A head butt or cheek rub from a cat is its way of saying "this human is mine". It's a sign of true affection from your feline companion.