Why Do Cats Open Their Mouth When They Smell?

Have you noticed your cat opens its mouth when it smells and leaves it open for a little while afterward? This is common in cats – they’ll smell something, leave their mouth open, and gaze off into the distance. This behavior is what is known as the flehmen response, better known to cat owners as “stinky face”.

Despite its funny name and strange facial expression, the flehmen response in cats is pretty serious stuff. It helps them to smell the odor or object better so they can determine what it is and process the scent more deeply.

Here I’ve put together all there is to know about why cats hold their mouth open when they smell, why it is important, and other things to consider about our cats’ little noses!

I’ve also covered some of the medical conditions associated with a cat keeping its mouth open so you know when to worry and when to not.

What is the Flehmen Response?

The flehmen response is where a cat leaves its mouth open for a little while after smelling. Your cat will curl back its top lip, leaving its front row of teeth and gums exposed. Your cat will hold this facial expression for a little while as they continue to breathe and inhale through both the nose and mouth.

This facial expression may look a little strange to people, looking like a snarl or a grimace. As such, many people think felines pull this face when cats smell something bad. Now, don’t get me wrong, there are smells that cats hate which they may turn their noses up at! However, your cat making weird mouth movements when smelling is not their way of saying “ew!”.

Instead, this response serves an important function. By curling their lip backward and leaving their mouth open, scents can travel not only up to your cat’s nose but also through their mouth to a specialized area called the vomeronasal organ.

The vomeronasal organ, otherwise known as Jacobson’s organ, is located inside the roof of your cat’s mouth. This is an area that contains lots of sensory cells. In particular, this region contains olfactory cells which respond to odors. When the odor latches onto these cells, the vomeronasal organ sends signals to the hypothalamus in your cat’s brain letting them know what smell lies before them.

By using both the olfactory sensory cells in the nose and Jacobson’s organ, cats have an extremely fine-tuned sense of smell. In fact, their ability to detect and pinpoint smells is 14 times better than that of humans. For this reason, smell is the primary sense that cats use to identify objects and people.

Our cute domestic felines are not the only animals to have these olfactory receptors and smell with an open mouth. Another of the world’s favorite pets – dogs – also have a vomeronasal organ. However, where cats have over 30 different receptor types, dogs only have nine. Still, they too show the flehmen reaction in response to smell.

Other mammals also have Jacobson’s organ, including horses, sheep, antelopes, elephants, giraffes, pandas, and big cats such as tigers and lions. All of these animals also exhibit “stinky face”, a.k.a holding their mouth open and smirking when they smell.

What is the Purpose of the Flehmen Response?

So, we now know why cats smell with an open mouth – it means they can smell the object or person in front of them more effectively. But what is the purpose of this? Why do cats need to be able to smell so precisely? According to scientists, there are actually several important reasons, and this all boils down to pheromones.

Pheromones, sometimes called scent hormones, are what cats use to communicate with one another. They are produced and released by all cats, and no two cats’ pheromones smell the same. While humans cannot detect these pheromones, cats can easily thanks to the fact that cats smell with an open mouth.

Therefore, pheromones and the flehmen response play an important role in intraspecies communication. When cats smell with an open mouth, they aren’t just smelling any old smell – they’re specifically smelling these pheromones.

For better understanding, below are just some examples of what felines can detect when cats hold their mouth open when smelling.

1. Finding Females in Heat

If you have a male cat, you may notice that the flehmen response is much stronger. This is because one reason why cats open their mouth when they smell is that it plays an important role in the mating process.

When female cats are in heat, their pheromones echo this. So, if a tomcat smells the pheromones of a female cat that is ready to mate, they will immediately know she is in heat with one quick sniff. Therefore, males will often smell with their mouths open as they are much more perceptive of pheromones and don’t want to miss the opportunity to mate.

2. Knowing Whose Territory They’re in

Cats are independent and territorial creatures, and pheromones play an important role in territorial marking. When cats smell with an open mouth and pick up the pheromones of another cat, they are immediately made aware that they are in the vicinity of another feline.

You’ll often see your cat spreading its pheromones around your home if you’re watching closely. Pheromones are predominantly released from the glands between their toes and on their cheeks, chin, ears, and forehead. Next time you see your cat rubbing any of these areas on a person, object, or the floor, they are likely transferring their pheromones and marking it as their own.

3. As a Form of Identification

Smelling another cat with an open mouth will let your cat know who it is they are in the presence of. As no two cats have pheromones that smell the same, cats use this scent as a form of identification. Another cat’s scent will inform them of who they are talking to and whether they have met before.

Mother cats may also use the flehmen response and smell their kittens with an open mouth to help keep track of them. As each kitten will smell unique, they can easily tell which is which and ensure that they are all safe and sound.

What Scents Do Cats Smell With an Open Mouth?

You may have noticed that your cat doesn’t always open its mouth when they smell and pull a weird facial expression. Likely, your cat will only do this in response to certain smells or when sniffing certain objects or parts of your home. So, what scents trigger the flehmen reaction?

1. Urine and Feces

As already mentioned, the flehmen response is used to specifically smell and identify feline pheromones. Therefore, one of the most common scents cats smell with an open mouth is urine and feces from another cat, both of which contain high levels of pheromones.

As such, outdoor cats may smell urine or feces that they come across on their adventures with an open mouth. To humans, cat urine and feces smell disgusting! But to cats, they want to learn as much about where they came from as possible. It tells them who’s been nearby, whether someone has encroached on their territory, or whether they’re tiptoeing on someone else’s space!

It is important to note that cats won’t tend to smell their own urine or feces with an open mouth. They already know what they smell like and don’t need a better understanding of their own scent.

2. Litter Boxes

If you have one cat, you won’t often see your cat open its mouth after smelling its litter box. Again, it knows its own smell like the back of its hand and doesn’t need any more information on this.

However, in a multicat household, you may see an open mouth smelling around a shared dirty litter box. As this is where all your cats are going to the toilet, there are lots of pheromones floating around that your felines may wish to discover more about.

If there are too many smells in your cats’ litter box, they may refuse to use it full stop. Try giving each of your cats their own litter box so that the odors and pheromones don’t concentrate in one place. Not only will your cats thank you for this, but your home will smell nicer and you’ll have fewer toilet accidents to clean up!

3. Random Home Objects

If you have more than one pet cat, other items in your home that are high in pheromone levels will also trigger the flehmen response. Scratching posts and cat trees contain high levels of pheromones that have been transferred from your kitty’s paw pads to the object. As such, you may see your cats hold their mouth open after sniffing their cat tree.

Many items of furniture can also smell like other cats. It is common for cats to brush up and rub on things like your couch and bookcase, and when doing so they will transfer these pheromones from their faces and bodies to the object in question.

Unfortunately, cats that make the open mouth face when smelling might be doing so as they can smell urine. Therefore, it is important to see if one of the cats in your home is urine marking. This is quite common, especially in unneutered males cats, and is a way of marking their territory.

Of course, as a homeowner, having cat urine up your walls and on your furniture is the last thing you want! If your cat is spraying, you should start by getting your cat neutered if they haven’t been already and seeing if this stops the behavior. If not, they may be stressed or have a urinary problem, so take them to the vet for advice and treatment.

Health Conditions Where Cats Hold Their Mouth Open

In most cases, it is completely normal for cats to open their mouth when they smell. It is their way of learning more about the chemical pheromones in the area, letting them know more about nearby cats. However, your cat should not open their mouth after smelling all the time, and this could be a sign something is wrong.

In fact, aside from when sniffing an interesting smell, a cat will keep its mouth shut the majority of the time. If your cat’s mouth is hanging open all the time, it can be alarming and is linked to several medical conditions! Examples of some such health conditions include…

1. Asthma

Some cats may suffer from asthma, which restricts their airways and makes it difficult for them to breathe. As such, your cat may sit with its jaw ajar and start breathing through its mouth. Although cats can breathe through their mouth, constant open-mouth breathing is typically a sign something is wrong.

Alongside holding their mouth open often, other signs of asthma include wheezing, loud breathing, weakness, and lethargy. In some cases, the lack of air can also make your cat feel nauseous and start vomiting. If you think your cat has asthma, take them to the vet so they can prescribe medication to help them breathe easy once more.

2. Respiratory Infections

Respiratory infections, especially those of the upper respiratory tract (URI), can also cause open mouth breathing in cats. Approximately 80% of all URIs are caused by viruses, such as the Feline Herpesvirus and the Feline Calicivirus. The remaining 20% are caused by bacterial infection.

Regardless of the cause of the respiratory infection, symptoms will be similar as the pathogens are targetting the nose, throat, and sinuses. Symptoms therefore include:

• Sneezing and coughing
• Discharge from the eyes and nose
• Sinus congestion
• Open-mouth breathing

3. Heatstroke

There is also a chance that your cat has its mouth open as it is suffering from heatstroke and trying to cool itself down. Think of a dog panting on a hot summer’s day or after going on a big run. Holding their mouth open and drooling can help them cool down and return to an optimal body temperature. This works the same for cats.

Heatstroke is dangerous for cats as if your cat cannot cool themselves down them their body temperature will continue to increase. Eventually, this will cause their heart rate to become faster and faster, leading to seizures and, in worst-case scenarios, death.

As such, it is important to recognize the signs of heatstroke as quickly as possible so that you can do your bit to help your cat cool down. Alongside drooling, other signs of heatstroke that you can look out for include:

• Swollen and red gums
• Reluctance to move and exercise
• Increased tiredness and sleeping
• Sickness and/or diarrhea

Is your cat drooling but acting normal? If you notice your cat drooling but none of these other symptoms then you’re probably in the clear. Drooling can be a normal part of life for a cat!

4. Dental Diseases

Your cat could also be holding their mouth open more than usual as they are suffering from dental diseases. Two of the most common dental conditions in our furry feline friends are gingivitis and stomatitis. Both of these conditions can make your cat’s teeth and gums extremely painful.

When their mouth is in so much pain, it may be comforting for them to hold it slightly open. In addition to holding their mouth open, cats with dental diseases will have inflamed and swollen gums that might bleed when touched. These cats also usually have bad breath.

If you think your cat has dental disease, a trip to the vet is a must! These illnesses are progressive and will gradually get worse if the plaque and tartar that have built up are not cleaned away. If caught early, cleaning away the plaque may be enough to ease your cat’s pain. In more severe cases, tooth removal may be required.

5. Nasal Cavity Tumors

Cats can develop tumors anywhere in their bodies, including the nasal cavity. These tumors are rare, but as the tumors grow they will obstruct the nasal passage and make it difficult to air to flow. In these cases, cats may hold their mouth open and start open mouth breathing.

In addition to having an open mouth, cats with nasal tumors show many other symptoms. In the early stages of the disease, you may notice your cat keeps sneezing but seems fine. As the tumor grows, other symptoms are also present, including bloody discharge from the nose, pawing at the face, and loud snoring in cats.

As the tumor gets bigger, your cat’s face will start to swell. Depending on the precise location of the tumor, their eyes could bulge and push our discharge. Where the tumor presses down on the brain, seizures are another possibility.

Should I Take My Cat to the Vet?

As cat owners, we obviously love and care for our furry friends deeply. Therefore, when we see a strange behavior such as when cats hold their mouth open, it can send us into a frenzy! We immediately panic that something is wrong and want to do everything we can to fix the issue.

However, before you panic, have a read back through everything in this article and ask yourself the following questions.

Does Your Cat Have an Open Mouth After Smelling?

If you answered yes to this question, there is likely nothing to worry about. This is the flehmen response and is simply a method of smelling that your cat uses to accurately find as much out about the nearby odor as possible. This is especially true if your kitty is smelling cat urine or feces. It is also likely if you live in a multicat household that will be full of different pheromones from all of your furry friends!

Does Your Cat Have Its Mouth Open All the Time?

If your cat has its mouth open all the time, this usually means one of two things: (1) your cat is breathing through its mouth, or (2) it is causing your cat pain and discomfort to hold it shut. In either of these cases, this is usually a sign that something is wrong. Happy and healthy cats tend to keep their mouths closed most of the time. Therefore, if you answered yes to this question it could be time to take your cat to the vet.

Is Your Cat Showing Other Signs of Illness?

If your cat is keeping their mouth open constantly and showing other signs of illness, this is a definite indication that they need medical attention. Some of the key symptoms to look out for include lethargy, loss of appetite, fever, difficulty breathing, coughing, and sore/swollen gums. Take your kitty to the vet as soon as possible for an accurate diagnosis. From here, your vet will be able to prescribe treatment and ensure your cat is back to its usual happy selves in no time at all.

MY FINAL THOUGHTS

So, why do cats open their mouth when they smell? This strange response to odors is a cat’s way of finding as much out about this scent as possible. Thanks to their mouth being open, the odor molecules can attach to olfactory receptors on Jacobson’s organ. This organ sends precise signals to the brain, informing the cat of exactly what scent they can smell.

This flehmen response is crucial for intraspecies communication. The receptors here can pick up chemical pheromones, informing cats about who has been in their vicinity, whose territory they are in, and if there is a female in heat close by. As such, smelling with an open mouth is actually beneficial.

However, when cats hold their mouth open all the time this can indicate several illnesses. These range from respiratory tract infections to asthma, nasal cancers, dental diseases, and more!  If unsure whether or not something is wrong, I advise you to take a trip to your vet.