Why Do Cats Keep Their Mouths Open?

Many cat owners notice that their cats sometimes make strange faces. It may look like a grin or the baring of fangs when cats hold their mouths slightly open. Although this sight may be irritating in the early morning, it is normal behavior for a cat. It is rarely aggressive unless you notice other signs of hostility accompanying it.

Most of the time, cats hold their mouths open to smell pheromones. This is called the flehmen. Cats have an organ in their mouths that allows them to analyze scents. To access this organ, they must open their mouths and encourage airflow through Jacobson’s organ or vomeronasal organ. In this way, cats can detect nearby conspecifics, kittens, food, and other cats’ territories.

However, there are also cases where an open mouth indicates dental pain or health problems.

Cats with inflamed gums or teeth will keep their mouths open to relieve discomfort.

Your cat may also have breathing problems or a growth in his throat that prevents him from using his voice. In these cases, there are also other apparent symptoms you can recognize.

Why Do Cats Keep Their Mouths Open?

Cats orient themselves in their world mainly by smell. They have over 200 million sensors in their nose responsible for their sense of smell.

Cats also rely on the inside of their mouths to make their olfactory perception even more effective.

While dogs often leave their mouths open out of habit, cats usually do so to detect an odor accurately.

It may seem strange to see your cat sitting on the floor with its teeth slightly bared and its mouth open. However, this is an advanced form of sniffing.

In rare cases, however, this may mean that your cat has a toothache or is suffering from respiratory problems.

She may be trying to articulate; if she is upset, she may be preparing to bite.

Let’s now go into more detail about all of these possible reasons.

Unusual Smells

When your cat holds her mouth open, especially if it is a male cat, she will most likely react by the flehmen response.

The term flehmen comes from an Upper Saxon verb meaning “to bare the upper teeth or curl the lip.” It means that an animal opens its mouth to take in an exciting smell more closely.

When a cat takes in air through its mouth, it can let it flow in through an organ.

This is called the Jacobson’s organ or vomeronasal organ (VNO), which can analyze smell. This sense is a combination of taste and smell.

Cats use the flehmen response, especially when they smell pheromones. In particular, they detect the pheromones in urine left to mark territory or by a cat in heat.

Cats use pheromones to communicate specific messages with other cats and to identify different cats.

These pheromones usually come from urine or feces. Although all cats exhibit flehmen, male cats do so most often.

They are more receptive to sex-related information, even if they are neutered. Now, let’s look at other ways cats can use flehmen to limit odors.

Urin to Mark Territory and for Identification

Male cats use urine to mark their territory, especially if they are not neutered. In fact, this is one of the most common reasons cat owners have their cats neutered.

If you have multiple male cats in a household or other cats nearby, the unneutered cats will likely start urinating around the house. This is their attempt to mark their territory before the other cats.

Both male and female cats will spray urine. This is because cat urine contains pheromones that inform other cats of their age, sex, and other factors.

Cats are much better at analyzing these scents using the Jacobson organ on the roof of their mouths than they are with just their noses.

Once a cat has analyzed this scent, it can determine whose territory it is on. Based on this information, she can feel welcome or threatened there.

Cats in Heat

A male cat also uses flehmen to find a female to mate with. When a female cat is in heat, she releases pheromones to invite males in the area to approach her.

She is ready to mate, and the males should know that. So when a tom cat senses a mating signal in the air, he can start bunting.

This gives him a better idea of who the signals belong to and helps him determine where the female cat is.

This is an essential skill for outdoor or feral cats. Otherwise, they cannot easily find a mate and reproduce.

Once the female is pregnant, she stops releasing these pheromones. However, this is only true for cats that have not been neutered.

Neutered cats no longer release these mating signals because they can no longer be in heat.

Mother Cats and Their Kittens

After birth, mother cats use pheromones to identify their kittens.

A mother cat keeps her mouth open to smell these pheromones and find the location of her kittens after leaving them briefly to hunt.

The mother also releases pheromones in her milk. This serves two purposes:

It calms the excited kittens. For this reason, some people use a pheromone diffuser on anxious or restless cats. The product sprays a chemical into the air that mimics the pheromones in breast milk.

It can help reduce your cat’s stress due to environmental changes. They will feel the same calmness that she experienced as a kitten. This will reduce scratching or urine spraying in the house.

In addition, the pheromones in the mother’s milk serve as a guide to help the kittens find each other and their mother.

For example, a kitten may accidentally stray from its litter and get lost.

If it remembers the pheromones in its mother’s milk, it can follow that trail back to its hiding place.

Food Or Catnip

Cats obviously respond to the smell of food. If the meal is too far away or the cat is unsure, she will start baaing.

If she finds the smell particularly enticing, she may even open her mouth to sniff the food up close. This is usually the case with catnip.

Some cats can interpret the smell of catnip as cat pheromones. This is why some cats overreact to the herb, whether they are male or female.

How your cat reacts depends on their personality and biology.

Some cats are very affectionate, relaxed, and happy. Other cats are playful or even aggressive. Some avoid catnip altogether.

According to scientific research, only about 60% of adult cats actively respond to catnip. However, almost 100% react at least passively to it.

For cats that do react positively to catnip, it can help relieve anxiety and even pain.


Of course, there are situations when your cat, with its open mouth, not only smells the air. Sometimes, the cat keeps its mouth slightly open because it has a toothache.

This prevents the teeth from touching, which limits the pain. It can also encourage airflow over inflamed gums or sores that need relief.

The most common causes of oral pain in cats are gingivitis and stomatitis.


Gingivitis, or inflammation of the gums, is a common dental problem in many animals, including cats. It occurs when plaque builds up on the teeth.

If your cat suffers from gingivitis, it is crucial to treat it soon. Gingivitis can lead to periodontal disease, resulting in the loss of an affected tooth.

Signs of gingivitis include:

  • Inflamed gums (gums swell and appear red)
  • Lethargy
  • Pain when eating (your cat may chew on only one side of the mouth, meow while eating, or stop eating altogether)
  • Bad breath (your cat smells worse than usual)


Cats may also suffer from pain in the mouth caused by stomatitis, an inflammation of the lining of the mouth. It is also known as chronic gingivostomatitis.

The condition is described as a chronic, painful inflammation of the oral mucosa or the back of the mouth. The cause is not exactly known, but it is associated with an autoimmune reaction.

The signs of stomatitis are:

  • Bright red gums that bleed easily.
  • Bad breath
  • Drooling
  • Excessive swallowing
  • Paw marks on the face
  • Difficulty eating or with personal hygiene.

There is no cure for stomatitis. Tooth extraction, however, may be a reasonable solution for stomatitis in many cats.

In one study, 39% of subjects experienced significant improvement with tooth extraction. In 28.4%, there was even a complete cure of the stomatitis.

So, this treatment is not practical for every cat. However, if your pet suffers from stomatitis and is in severe pain, you can talk to your veterinarian about tooth extraction.

Your veterinarian may also recommend other treatment options better suited to your pet.

Difficulty Breathing

Your cat may be holding her mouth open because she has difficulty breathing.

Their nose could be blocked due to allergies, infections, or tumors. This causes your cat to breathe in air through his mouth rather than nose.

If this is the case, your cat is very stressed. You will see her gasping for air, breathing deeper, and sometimes appearing distressed.

In rare cases, your cat may be experiencing acute respiratory distress, usually caused by the following.

  • Heart disease
  • Lung disease
  • Feline infectious peritonitis (FIP)
  • An injury to the cat’s rib cage.

This condition can escalate and cause your cat to need oxygen immediately. Watch for these symptoms:

  • Panting and difficulty breathing
  • Refusal to move
  • The head is lowered, and the legs are pulled away from the chest and body
  • Coughing
  • Bluish gums, indicating low oxygen levels in the blood

Attempt to Verbalize

Less alarmingly, cats that hold their mouths only slightly open are preparing to raise their voices.

Although cats express themselves mainly through body language, they also communicate through their voice. They do this by meowing, hissing, and purring.

If your cat opens her mouth but doesn’t make a sound, she may be indecisive. She is thinking about what sound she will make and whether she should make it.

However, cats are pretty decisive creatures, so this is an unusual habit for your cat.

However, it may be that the cat hesitates because it can’t make a sound or is not readily available to it. In that case, this gesture is quite typical for your cat.

She may be struggling with a health problem:

  • Laryngeal obstruction
  • Swelling of the lymph nodes under the jaws
  • Nerve damage to the larynx, called laryngeal paralysis.

Announce a Bite

Some cats hold their mouths open when they announce and prepare for a bite.

If you pet your cat while this happens, it could be a warning to stop. The cat is not enjoying it anymore and is letting you know.

Watch for other signs of aggression, such as:

  • Fidgeting
  • Tensing
  • Growling
  • Hissing

This is a clear sign that your cat is threatening to bite. You should give her space until she relaxes or calms down.

Summary: Why Do Cats Keep Their Mouths Open?

Cats holding their mouths open is usually perfectly normal. She probably smells the air or wants to say something.

However, you should pay attention if symptoms of health problems accompany this. It may also be a sign of a medical issue.

And if the cat seems to be agitated while holding its mouth open, you should leave it alone until it calms down.