Mouth Slightly Open in cats

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026
Table of contents

When to visit the vet?

Non-urgent see a veterinarian within 2–3 days

?

ORANGE if new and persistent, if drooling, swallowing problems, mouth odor, refusal to eat, or pain are present. RED with mouth breathing/dyspnea, trauma, significant tongue protrusion/swelling, or altered consciousness.

Unsure about what’s wrong with your pet? Feel free to use our Symptom Checker for more clarity

Definition

The symptom ‘mouth slightly open’ in cats describes a condition in which the cat does not fully close its mouth and keeps it in a slightly open position. This behavior can indicate a variety of health problems ranging from harmless to serious.

Can Occur with the Following Diseases:

Basics and possible causes

Cats open their mouths for various reasons, which can range from anatomical to pathological causes. One of the most common causes is a problem in the oral cavity, such as dental or gum disease. Pain or discomfort in this area can cause the cat to not want to fully close its mouth. Tartar (calculus), tooth fractures, or gum inflammation are common triggers here.

Another possible cause is a respiratory disease. If the cat has difficulty breathing through the nose, it may try to breathe through the mouth, resulting in a slightly open mouth. Upper respiratory infections, such as those occurring with cat flu, can cause the nasal/pharyngeal tissue to swell and thus obstruct nasal breathing.

Neurological problems can also cause a cat to keep its mouth slightly open. These can arise from damage to the central nervous system or from muscle problems that impair the normal function of the chewing and facial muscles.

Finally, stress or anxiety can also cause a cat to open its mouth, as this is often associated with increased breathing or the so-called ‘flehmen,’ a behavior in which cats perceive new scents more intensely.

Typical accompanying symptoms

  • Increased drooling: When the mouth is slightly open, increased drooling may occur as the cat has difficulty controlling saliva flow. This can indicate a problem in the oral area, such as gum disease or an injury to the oral mucosa.

  • Breathing sounds: An open mouth can be accompanied by breathing sounds, especially with respiratory diseases. These sounds can be perceived as rattling, snoring, or wheezing and indicate a blockage or narrowing of the airways.

  • Loss of appetite: Pain or discomfort in the mouth can cause the cat not to eat or want to eat. This can quickly lead to weight loss and further health problems.

  • Behavioral changes: A cat in pain may withdraw, become aggressive, or appear generally stressed. Its behavior can change drastically when suffering from a health problem.

  • Limited mobility of the jaw: Difficulty opening or closing the mouth may indicate a jaw problem or neurological causes that affect the mobility of the jaw.

When to see a vet?

A veterinarian should be consulted if the symptom of an open mouth persists for more than one day or is accompanied by other alarming symptoms. These include respiratory distress, visible pain, loss of appetite, or extreme behavioral changes.

Also, if the mouth is drooling heavily or has an unpleasant odor, this may indicate a more serious condition requiring immediate veterinary care. Cats are masters at hiding pain, so it’s important to take even subtle changes seriously.

A quick visit to the vet is also necessary if the cat no longer behaves normally, such as avoiding play or social interaction, or if it shows signs of respiratory distress, such as wide-open nostrils, a pumping abdomen, or a bluish tongue.

Symptom recognition for the pet owner and veterinary diagnostic procedure

For the pet owner, it’s important to closely observe the cat’s behavior and document all changes. This includes the frequency of the open mouth, the duration of the symptom, and possible triggers or accompanying symptoms such as eating, drinking, or movement behavior.

The veterinarian will first perform a thorough clinical examination. The veterinarian will examine the cat’s oral cavity, teeth, and gums to identify possible abnormalities or injuries. The airways will also be inspected to rule out breathing problems.

In some cases, further diagnostic measures may be necessary, such as X-rays to check the structure of the jaw, or blood tests to detect signs of inflammation or systemic diseases. In some cases, a CT or MRI scan may also be necessary to identify neurological problems.

What the pet owner can do and professional therapy options

Until the veterinarian can examine the cat, certain precautions should be taken to avoid further stress or harm. Ensure that the cat has access to fresh water and remains in a quiet, stress-free environment.

It’s important not to force the cat to close or open its mouth, as this can cause pain. Instead, try to minimize stress and support the cat through gentle reassurance.

If the cat has difficulty eating, it may be helpful to offer soft food that is easier to chew and swallow. This can reduce the strain on the mouth while ensuring the cat continues to receive nutrients.

Outlook on current research

Current scientific studies are intensively examining the physiological and neurological aspects that cause cats to keep their mouths slightly open. A particular focus is on the role of the Jacobson’s organ, a sensory organ that plays an important role in the sense of smell and taste in cats. Researchers are investigating how this organ, in connection with other sensory systems, influences the cat’s behavioral responses, especially in situations that trigger stress or agitation.

Another interesting research approach examines the genetic predispositions that might cause cats to keep their mouths slightly open. By analyzing genetic markers, scientists can better understand whether there are certain breeds or lines that are more susceptible to this behavior. Such genetic studies could help in the long term to develop selective breeding strategies to improve the well-being of cats.

Additionally, there are studies examining the effects of environmental factors on this symptom. For example, research is being conducted on how noise pollution, air quality, and the presence of other pets in the household can influence a cat’s behavior. These studies could help create better living conditions for cats that reduce the occurrence of symptoms such as a slightly open mouth.

Furthermore, the role of stress and anxiety as triggers for the symptom ‘mouth slightly open’ is being further investigated. Scientists are exploring which specific stressors trigger this behavior and how stress management techniques, such as pheromone therapies or enriched environments, can positively influence cat behavior. The results of such studies could provide important insights for pet owners and veterinarians.

Finally, some researchers are working on developing new diagnostic tools that enable more precise monitoring and analysis of cat behavior. These technologies could range from computer-assisted behavioral analyses to wearable devices that measure physiological parameters. Such innovations could revolutionize the detection and treatment of behavioral abnormalities in cats.

Frequently asked questions

1. Why does my cat keep its mouth slightly open?
Cats slightly opening their mouths can occur for various reasons, including flehmen behavior, in which the cat takes in pheromones, or health problems such as dental or respiratory diseases. It's important to observe the behavior in the context of other symptoms.
2. Is the slightly open mouth in my cat an emergency?
In most cases, a slightly open mouth is not an emergency, but it can indicate an underlying problem. If the cat shows additional symptoms, such as shortness of breath or heavy drooling, a veterinarian should be consulted.
3. Can stress cause my cat to keep its mouth slightly open?
Yes, stress can be a factor contributing to this behavior. Cats are sensitive to changes in their environment, and stress can manifest in physical symptoms.
4. How is the Jacobson's organ related to a slightly open mouth?
The Jacobson's organ, also called the vomeronasal organ, plays a role in flehmen behavior, in which the cat slightly opens its mouth to better perceive pheromones. This is normal behavior and serves communication and orientation.
5. Should I worry if my cat keeps its mouth slightly open but otherwise seems healthy?
As long as the cat shows no other symptoms and its behavior remains normal, there is usually no cause for concern. However, if the behavior occurs frequently or intensifies, it's advisable to consult a veterinarian.
6. Can dental problems cause a cat to keep its mouth slightly open?
Yes, dental problems such as gingivitis or tooth fractures can cause pain that causes a cat to keep its mouth slightly open to relieve the pressure.
7. Are there certain breeds that tend to keep their mouths slightly open?
Currently, there are no specific breeds known to more frequently keep their mouths slightly open. However, there are indications that genetic factors could play a role, which is the subject of ongoing research.
8. How can I tell if my cat's slightly open mouth indicates a medical problem?
Watch for additional symptoms such as sneezing, cough, loss of appetite, or changes in behavior. Such symptoms may indicate a medical problem requiring veterinary examination.
9. Can excessive noise pollution cause my cat to keep its mouth slightly open?
Yes, loud noises can trigger stress and anxiety in cats, which can manifest in physical symptoms such as a slightly open mouth. A quiet environment can help lower stress levels.
10. How can I help my cat if it keeps its mouth slightly open?
Ensure that the cat lives in a stress-free environment and offer plenty of opportunities for mental and physical stimulation. If the behavior persists, consult a veterinarian to rule out possible medical causes.