🐱 Vet Guide 2025: Understanding Your Cat’s “Sneer” – The Flehmen Response 👃

By Dr. Duncan Houston BVSc – Veterinarian & Founder of Ask A Vet

Have you ever noticed your cat sniff something and suddenly curl their lip, open their mouth, and freeze in a dramatic expression? It might look like a grimace—but it's actually a fascinating, instinct-driven behavior known as the Flehmen response (or “stinky face”). In this deep-dive 2025 vet guide, we'll explain *what it is*, *why cats do it*, *when it's normal*, and how understanding it strengthens your bond. 🧬

🔍 1. What Is the Flehmen Response?

The Flehmen response is a deliberate behavior where your cat curls back its upper lip, exposes its front teeth, opens its mouth, and inhales—directing scent molecules towards a special sensory structure called the vomeronasal organ (Jacobson’s organ) located in the roof of the mouth :contentReference[oaicite:3]{index=3}.

This facial expression helps cats detect pheromones—chemical signals used for communication about territory, reproduction, and identity :contentReference[oaicite:4]{index=4}.

👃 2. How It Works: Jacobson’s Organ in Action

When your cat performs the Flehmen response:

• The upper lip lifts, and the mouth opens
• Air bypasses the nose, flowing over the roof of the mouth
• Scent travels through ducts into the vomeronasal organ
• The brain processes these signals like a mix of taste and smell :contentReference[oaicite:5]{index=5}

This behavior is seen across mammals—from big cats and horses to goats and rhinos :contentReference[oaicite:6]{index=6}.

🧬 3. Why Cats Use It: Common Triggers

Your cat may snarl their lips after sniffing:

• Other cats’ urine or faeces (territorial/pheromone signals) :contentReference[oaicite:7]{index=7}
• A female in heat (especially in unneutered males) :contentReference[oaicite:8]{index=8}
• New or strong aromas: catnip, fabrics, human sweat, plants :contentReference[oaicite:9]{index=9}
• Smells from kittens or mother-newborn pheromones :contentReference[oaicite:10]{index=10}

📸 4. What the Flehmen Response Looks Like

Watch for this sequence:

• Lip curl exposing teeth
• Mouth slightly agape
• Head tilt up or neck stretch
• Quiet pause, “frozen” expression lasting a few seconds :contentReference[oaicite:11]{index=11}

This is not panting or sneezing—no distress, just analysis.

✅ 5. When It’s Totally Normal

• Investigating new, significant scents
• Sniffing other cats’ markings or feces
• Sniffing catnip or strong-smelling items
• Detecting pheromones like feline appeasing, facial, or mating signals :contentReference[oaicite:12]{index=12}

This is healthy, instinctive, and even beneficial—don't interrupt!

⚠️ 6. When to Be Cautious

If your cat’s “grimace” is accompanied by:

• Rapid open-mouth breathing or panting (possible respiratory issue)
• Drooling, pawing at mouth—can signal dental pain or nausea
• Frequent sneezing or nasal discharge—possible infection or irritant
• Other signs of stress or discomfort

Then it's time for a vet check, as these are not Flehmen but health red flags :contentReference[oaicite:13]{index=13}.

💬 7. Fun Facts & Social Role

• The Flehmen response helps cats interpret breeding, territory, or emotional states of others :contentReference[oaicite:14]{index=14}
• Kittens use it too—sniffing mother’s pheromones for security :contentReference[oaicite:15]{index=15}
• Pronounced in unneutered males for mating behavior detection :contentReference[oaicite:16]{index=16}
• Also observed in deer, goats, big cats, horses, and other mammals :contentReference[oaicite:17]{index=17}

👂 8. How to Respond as a Vet-Recommended Guide

• Stay calm—this behavior is normal, so let them finish
• Offer soft interaction afterward—petting, slow blinking helps bonding
• Use vet-guided enrichment: toys, vertical perches, and scent-safe spaces
• Consult Ask A Vet if they show repeated distress behaviors with sneering

📲 9. Ask A Vet Support 2025

Your Ask A Vet app helps with:

• Video/photo analysis of sneering behavior
• Assessing if underlying issues like dental pain or respiratory irritation exist
• Creating enrichment plans to encourage healthy scent exploration
• Referring for in-person vet care if abnormal behaviors appear

With expert guidance, you can understand whether your cat’s faces are sniff-curious or sniff-sick. 📞

🧠 Final Thoughts

The Flehmen response is a natural and intelligent behavior—a scent-driven communication tool cats use to understand the world. Recognizing it as normal helps you avoid overreacting. But if it’s mixed with stress or health signals, ask your vet. Either way, these curious expressions are just another reminder of how complex—and adorable—cats truly are. 🐾

Download the Ask A Vet app today for real-time behavior support, interpretation, and peace of mind. 📲🐱