The Flehmen Response: Unpacking Your Cat’s ‘Stink Face’

If you’re a cat owner, you have likely seen it: your feline friend sniffs something with great interest, then lifts their head, curls back their upper lip, and holds a strange, sneer-like expression for a few seconds. This comical grimace, often called the “stink face,” is a fascinating piece of cat behavior known as the Flehmen response. It is not a sign of disgust; rather, it is a sophisticated method of investigation. At Pet Ponderosa, we are experts in decoding feline behavior. Understanding the Flehmen response is crucial for us to ensure your cat feels secure and understood while boarding. This guide explores the science behind this unique behavior and what it tells you about your cat’s world.

What is the Flehmen Response?

The word “Flehmen” comes from a German verb meaning “to bare the upper teeth.” The response is a specific behavior where an animal draws in scents to be analyzed by a specialized sensory structure. When a cat exhibits the Flehmen response, it is using an auxiliary olfactory sense organ to get a deeper understanding of a particularly interesting smell. This behavior is not unique to cats. Horses, goats, tigers, and even dogs use it. However, it is particularly pronounced in felines. The cat will press its tongue against the roof of its mouth to transfer scent molecules into a special organ designed for in-depth chemical analysis.

The Vomeronasal Organ: A Second Nose

The key to the Flehmen response is the vomeronasal organ, also known as Jacobson’s organ. This tiny, cigar-shaped structure is located in the roof of the mouth, just behind the front teeth, with two small ducts connecting it to the oral cavity. It functions as a specialized scent analyzer, detecting chemical cues that the regular olfactory system in the nose might miss. Think of it as a combination of taste and smell. While the nose detects airborne scents, the vomeronasal organ specializes in non-volatile, moisture-based chemical signals, particularly pheromones. Feature Nasal Olfactory System (Nose) Vomeronasal Organ (Jacobson’s Organ) Location Nasal cavity Roof of the mouth Function Detects general airborne odors Detects specific chemical cues (pheromones) Activation Normal breathing and sniffing The Flehmen response (lip curl and inhalation) Information Type General environmental scents Social and reproductive information

What Triggers the Flehmen Response?

A cat will use the Flehmen response when it encounters a scent that requires more detailed investigation. In a multi-cat environment like a home or a boarding facility, this is an essential tool for social communication. Common triggers include: •Urine and Scent Markings: This is the most common trigger. Cats use the Flehmen response to analyze the pheromones in other cats’ urine to determine their sex, reproductive status, and social standing. •New Objects: Unfamiliar furniture, toys, or a new carrier can prompt a Flehmen response as the cat investigates its origins. •Other Animals: The scents left behind by other animals, including dogs, are often analyzed this way. •Unfamiliar Environments: When you bring your cat to a boarding facility like Pet Ponderosa, they will likely use the Flehmen response to gather information about the other feline guests and the new territory.

When to See a Veterinarian

The Flehmen response is a completely normal and healthy behavior. There is no need for concern when you see your cat making this face. It is simply a sign that they are deeply engaged with their environment. However, if the lip curling is accompanied by signs of distress such as drooling, difficulty eating, or pawing at the mouth, it could indicate a dental issue. In such cases, a veterinary check-up is recommended. Our team at Pet Ponderosa is trained to distinguish normal behaviors like the Flehmen response from signs of medical distress, ensuring your cat’s stay is both enriching and safe.

Frequently Asked Questions (FAQ)

1. Is my cat disgusted when it makes the Flehmen response face?

No, quite the opposite. The cat is intensely interested in the smell and is concentrating on analyzing it. It is a sign of curiosity, not disgust.

2. Why does my cat make this face after smelling another cat’s rear end?

This is a primary way cats gather social information. The anal glands secrete pheromones that tell a cat everything it needs to know about the other cat’s identity, status, and health.

3. Do dogs have a Flehmen response?

Yes, dogs also have a vomeronasal organ and exhibit a Flehmen response, though it is often less dramatic than in cats. You might see a dog chatter its teeth or lift its lip slightly when investigating a scent.

4. How does this behavior help my cat at a boarding facility?

It allows your cat to safely and calmly gather information about its new surroundings and the other cats present. It is a low-stress way for them to understand the social hierarchy and feel more secure in the environment.

5. Can humans do the Flehmen response?

While humans have a vomeronasal organ, it is considered vestigial and non-functional in most people. The Flehmen response is not a part of human behavior.

Understand Your Cat Better with Pet Ponderosa

By understanding behaviors like the Flehmen response, we can better appreciate the complex world of our feline companions. At Pet Ponderosa, our deep knowledge of cat behavior allows us to create a boarding experience that is not just safe, but also mentally stimulating and emotionally supportive. Contact us today to learn how we cater to the unique needs of every cat.

References

[1] “What Is the Flehmen Response in Cats?” PetMD, www.petmd.com/cat/general-health/cat-sneering-what-flehmen-response. Accessed 23 Jan. 2026. [2] “What is the Vomeronasal Organ?” Cat Behavior Associates, catbehaviorassociates.com/what-is-the-vomeronasal-organ/. Accessed 23 Jan. 2026. [3] “Flehmen response.” Wikipedia, en.wikipedia.org/wiki/Flehmen_response. Accessed 23 Jan. 2026.