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Home > Cats > Why Do Cats Open Their Mouth When They Smell: 7 Vet-Approved Reasons

Why Do Cats Open Their Mouth When They Smell: 7 Vet-Approved Reasons

Portrait of a gray cat called Briton with open mouth

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Have you ever noticed your curious feline friend opening their mouth when sniffing something intriguing? It’s a peculiar behavior that sparks our curiosity. So, why do cats open their mouths when they smell?

Much like the curiosity of our feline friends, we too must also explore! In this article, we answer this question regarding feline olfaction with seven fascinating reasons!

divider-catThe Anatomy of a Cat’s Nose

To understand why cats open their mouths while sniffing, it’s important to explore the unique anatomy of their noses. Cats have a specialized sensory organ in their olfactory system called the Jacobson’s organ (also called the vomeronasal organ). This is located in the roof of their mouths and is composed of sensory cells that connect the cat’s olfactory and nervous systems. This organ plays a vital role in their sense of smell, helping them analyze and interpret scents and pheromones more effectively.

Image Credit: Mikhail Vasilyev, Unsplash

What Are Pheromones?

Pheromones are chemical signals that cats and other animals release to communicate with members of their own species. These special scents play a vital role in social interactions, marking territories, and conveying information.

While not detectable by humans, pheromones are a key element in the fascinating world of feline communication, helping cats establish their presence, convey emotions, and establish bonds with others.


The 7 Reasons Why Cats Open Their Mouths When They Smell

1. Flehmen Response

This is the main reason why cats open their mouths when they smell. The Flehmen response is a fascinating behavior exhibited by cats. By opening their mouths during sniffing, they facilitate the passage of odor molecules to the Jacobson’s organ, enhancing their ability to analyze scents and pheromones.

2. Sensory Exploration

Cats are natural explorers, and their open-mouth sniffing allows them to capture more scent particles. It helps them gather comprehensive information about their environment, enriching their sensory experience.

cat smelling cherry blossom flowers
Image By: Andréas BRUN, Unsplash

3. Scent Marking

Cats are territorial creatures, and by opening their mouths during sniffing, they can capture the scent on their mouths and distribute it through the Flehmen response. This behavior helps them communicate and mark their territory to other cats.

cat sniffing a rosemary plant on a balcony
Image Credit: Lifesummerlin, Shutterstock

4. Thermal Regulation

Cats are experts at maintaining their body temperature. Opening their mouths while smelling can serve as a means to dissipate heat, especially in warm environments or after physical exertion, helping them cool down.

5. Facial Expression

Cats are masters of non-verbal communication, and their facial expressions play a significant role in expressing their emotions. Opening their mouths while sniffing can be an instinctive facial expression that reflects their curiosity on the scent at hand.

6. Nasal Congestion

In some cases, cats may open their mouths during sniffing if they are experiencing nasal congestion or respiratory issues. By increasing the airflow through their mouths, they compensate for any difficulties in breathing through their nose, ensuring they can continue to get oxygen in their bodies. 

excited cat chattering or meowing with mouth open looking up
Image By: Nils Jacobi, Shutterstock

7. Dental Issues

Dental or oral health problems can also cause cats to open their mouths while smelling. If your cat is experiencing discomfort, inflammation, or pain in their mouth, they may exhibit this behavior as a response to dental issues.

Close-up muzzle of a short-haired American cat that sniffs and nibbles green grass on nature
Image Credit: DmitryStock, Shutterstock

divider-catIs This Behavior a Cause for Concern?

While opening their mouths when smelling is generally considered normal behavior, it’s essential to be aware of any changes in your cat’s behavior. If you notice excessive mouth opening, difficulty breathing, or signs of discomfort, it’s advisable to consult a veterinarian for a proper evaluation and guidance.

Do All Cats Open Their Mouths When Smelling?

No, not all cats open their mouths when smelling. While it is a behavior exhibited by many cats, it is not universal. Cats, like humans, can have individual preferences and variations in their behaviors.

Some cats may choose to keep their mouths closed while sniffing, and others may exhibit different behaviors altogether. It’s important to remember that each cat is unique, and their responses to different stimuli can vary. If your cat doesn’t open their mouth while smelling, there’s no need to be concerned. As long as your cat is otherwise healthy and displaying normal behavior, there is likely nothing to worry about.

white cat with its nose up
Image Credit: cottonbro studio, Pexels

How Do Cats Smell?

Cats have an incredible olfactory system that allows them to detect scents with astonishing precision. They possess around 200 million odor-sensitive cells in their noses, compared to our meager 5 million, making their sense of smell up to 14 times more powerful than ours!

Cats have various behavioral traits, and opening their mouths while smelling is one such behavior. While it’s challenging to determine the exact reasons for your specific cat’s behavior without further information, there are seven possible explanations for why cats may open their mouths when smelling!

When Should I Take My Cat to the Veterinarian?

Whenever your cat is open-mouth breathing, that is considered abnormal, since cats generally only breathe through their nose. If your cat’s abnormal breathing is also accompanied by other concerning signs, such as coughing, sneezing, nasal discharge, excessive drooling, or changes in appetite or behavior, it’s crucial to seek veterinary attention. These signs may indicate underlying health issues that require professional examination and treatment.

funny cat in domestic background, siesta time, relaxing cat, curious cat, cat with open mouth
Image Credit: Matthew Xan, Shutterstock



The next time you catch your cat opening their mouth during a sniffing session, you’ll have a whole new appreciation for their fascinating behavior. Cats open their mouths when smelling for a variety of reasons, including the Flehmen response, sensory exploration, taste involvement, scent marking, and more. It’s a blend of instinct, communication, and sensory enhancement.

As responsible cat guardians, understanding these behaviors helps us appreciate the remarkable abilities of our feline friends and ensure their well-being. So, embrace the adorable quirks of your cat’s sniffing adventures and enjoy the unique ways they perceive the world through their extraordinary sense of smell!

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Featured Image Credit: Anastasija Goryainova, Shutterstock

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