Why Do Dogs Always Keep Their Mouths Open?

Great Pyrenees mixed-breed dog lying down on green grass
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Dogs are adorable and, sometimes, adorably dopey looking. If you've ever noticed the derpy face of a dog who sits around all day staring at you lovingly with his mouth hanging wide opened and wondered, "Why are you making that ridiculous face" then this page is for you. Here's why your dog is constantly leaving their mouth open.

Why do dogs have their mouths open most of the time?

If it feels like your dog constantly has their mouth open, that's because an open mouth serves several functions for a dog. A dog's mouth plays a role in breathing, cooling, and communication, so there are a lot of reasons your dog might be slack-jawed. First, an open mouth is a great way for an overheated dog to cool down. It's also a way your dog might try to communicate with you — panting could be a sign of pain or fear (more on that below) while a soft open mouth (you know, that face that almost looks like a smile) communicates submissiveness and calm.

And, of course, dogs breathe through their mouths, so there's always that.

Why do dogs breathe with their mouths open?

If your dog is a major mouth-breather, there could be a number of reasons why. When a dog has just exercised or spent time in the heat, there's a good chance their mouth is open to help them cool down. Because dogs don't sweat through their skin like humans do, opening their mouths is their primary way of maintaining a cool and healthy body temperature.

Dogs also breathe with their mouths open when they're anxious or especially excited and happy (mixed signals, we know). If your dog is standing with his legs wide apart and his neck stretched out while they're open-mouthed breathing, take note — this could be a sign that your dog is having trouble breathing and needs to go to the vet immediately.

Why do dogs pant?

If your dog is panting in an excessive or weird way (not the usual "I'm super hot and trying to cool down, mom" pant you're used to), there are a few things that might be happening. Your dog may be scared or anxious and trying, in their own way, to ask for help during a stressful situation. It could also be your dog's way of trying to let you know they're in pain. The moral of the story: excessive panting should not be ignored.

Close-Up Of Dog
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Why do dogs sit with their mouths open?

If your dog is sitting still with their mouth open, it's time to look closer for clues. First, remember that an open mouth is your dog's personal air-conditioning system. If they've just been running around on a hot summer day, they might just be taking a literal breather to cool down. If that's not the case, here are the clues to look for.

Casually open mouth: If your dog's mouth is hanging open in a soft, casual position (lolling tongue optional), they're saying, "I'm having an awesome day and I love you so much." This open-mouthed face means your dog is totally content and calm.

Close-Up Of White Dog Sticking Out Tongue At Park During Autumn
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Moth open and panting heavily: Your dog is most likely over-heated. Give your best friend a drink of water and find some shade to cool off.

Corners of open mouth pulled back: This facial expression is known as a fear grimace, and it tells you a lot about your dog's emotional state.

Corners of open mouth pushed forward: This expression resembles a slightly puckered mouth. It tells you that your dog is willing to take an offensive stance and is feeling quite confident.

Baring teeth: If your dog is baring their teeth with an open mouth, however, it is not the time to snuggle. This is a signal of aggression and means your dog is majorly on edge. Maybe they feel threatened or afraid; whatever the case, the best thing you can do is be aware of any triggers in the environment and remove your dog from whatever is causing anxiety as soon as possible. If aggressive behavior continues, you should contact a professional trainer to get to the root of your dog's issues and help him overcome them and live a happier, more well-adjusted life.

Why do dogs open their mouths while playing?

If you've ever had a near freakout (or a full-on freakout, let's be honest) at the dog park because your dog lunged at one of her best friends with an open mouth, know that there's (probably) no need for alarm. Dogs often play with their mouths open, nipping, and jawing each other. This kind of play is called jaw sparring, and it's healthy and normal for dogs. While it might look like a fight, if there's no yelping or growling happening, know that the dogs are holding back and just having fun. It's like when human kids make fake cardboard swords and pretend to be knights fighting to the death — they're mimicking something dangerous, but in a pretty harmless way.

Two labrador retriever puppies wrestling and playing on green lush grass
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Why do dogs open and close their mouths repeatedly?

If your dog is opening and closing their mouth over and over, then keep an eye on them. While panting and open-mouthed breathing can be normal parts of a dog's life, repeatedly opening and closing the mouth is usually a sign that something is amiss. It could indicate something small, like a piece of food or a string from a recently demolished toy is stuck uncomfortably between their teeth or it could be something more serious, like a broken tooth, a sign of distemper, or even a neurological issue. It could also be a sign that your pet is feeling nauseous. Inspect your dog's mouth for foreign objects or obvious dental issues and, if the behavior continues, call your vet to be safe.

What causes excessive panting in dogs?

Open-mouthed breathing and panting can be traced back to several root causes. However, if panting becomes excessive and more than what's normal for your pup, it could be a real problem.

Some causes of excessive panting in dogs include:

  • Heatstroke
  • Poisoning
  • Illness
  • Allergic reaction

If your dog appears to be in distress, call your vet immediately. If your dog has been exerting themselves or it's especially hot out, get them somewhere cool and make sure your dog has access to plenty of cold water. If this doesn't help, get to the vet immediately.