Why Do Dogs Foam at the Mouth?

You know the stereotype of a rabid dog — the one of a dog foaming at the mouth and acting crazy? Well, there are a lot of other reasons why your dog could have problems with excessive drooling and frothing at the mouth. 

As a concerned dog owner, if you see your dog exhibiting what is technically known as hypersalivation, you want to know what’s causing it. Let’s look at some common reasons why your dog might be drooling too much, but let’s start with the basics — is there a difference between dog foaming and drooling? 

Dog Foaming Versus Dog Drooling

The distinction between foaming and drooling is important to understand since it can mean different things. Let’s take a look at how they’re different. 

Dog Drooling

why do dogs foam at the mouth

Drooling is something that can be completely normal. You’ve probably seen your dog drool on the occasion of his first car ride. You know what I’m talking about — the long strands of saliva hanging from the corners of his mouth. Now that’s excessive drooling!

Drool can also just appear as a kind of teardrop at the edge of your dog’s mouth, and some drooling is normal for your dog. It probably doesn’t concern you too much until it seems to magically turn into foam. 

Dog Foaming

Foaming or frothing appears much like the bubbles in your bubble bath, although these bubbles often also contain drool. It’s white and hanging off either side of your dog’s mouth. 

In actuality, dog foaming is a product of dog drooling. Foam or froth is simply drool that has been infused with air. This can happen due to dog panting or other kinds of heavy breathing. 

When he’s breathing heavily, the air movement inside your dog’s mouth is what causes the drool to froth, and that is what gives it a foamy appearance. But what does dog foaming or drooling actually mean? 

Why Do Dogs Foam at the Mouth? 

why do dogs foam at the mouth

There are several reasons why your dog might be foaming at the mouth, and only one of them is rabies. In fact, the numerous possible causes of dog foaming range in severity from nothing to worry about to Katie, bar the door! Let’s look at each possibility. 

Stress and Anxiety

This is probably one of the most common causes why dogs foam at the mouth. Stress can easily cause hypersalivation, heavy breathing, and other kinds of fearful behavior. When your dog starts breathing heavily, the movement of his mouth aerates the drool and turns it into a frothing foam at the corners of his mouth. 

That very thing likely happened when you took your dog for his first car ride, but it can also happen when he knows he’s going to the vet or when there is any other stressful situation that causes a nervous reaction in your pooch. 

Upset Stomach

a sleepy beagle on the couch. can dogs have depression?

That’s also a very common reason for frothing at the mouth, and it’s probably why your dog experienced hypersalivation and foaming when he took that car ride. If his upset stomach causes him to vomit, that can also cause frothing. 

If your dog’s frothing is caused by nausea, there might also be other symptoms to look out for like a lack of appetite, diarrhea, or a lack of energy which is also called lethargy. If you see those kinds of symptoms, it may be time for some veterinary care to check him out. 

Motion sickness, such as he might have experienced on that car ride, can also cause an upset stomach, so it may be nothing more serious than that. 

Too Much Activity

dog panting in the heat
pc: Sarina Morn

Another common cause of frothing at the mouth is over-exertion. Just like when you engage in vigorous exercise, it can also cause heavy breathing in your dog. Once again, the motion of air in your dog’s mouth can cause his drool to turn into froth. 

While some frothing is normal after exercise, you do want to be aware if it appears excessive. Too much frothing is a clear indication your dog needs a break from the activity. They can overheat or become too excited. 

That can result in erratic behavior and other serious health issues. It’s time to let your dog cool down, drink some water, and rest a bit. 

Bad Taste in Your Dog’s Mouth

Excessive drooling or frothing can also indicate your dog has tasted something bad. Dogs use their nose and mouth to sample the world around them, and they often get something in their mouth that doesn’t taste good. They also occasionally run into skunks and get sprayed — that definitely leaves a bad taste in their mouth!

Since your dog can’t flush the foul-tasting substance out of his mouth, it’s common to drool in response to that. That can easily turn into frothing, particularly if he’s eaten a plant, some kind of medication, or any other substance with a strong taste. 

You’ll want to pay attention if this is a possibility since he might have gotten into some toxic substance that might require a trip to the emergency vet. If the frothing gets worse and/or if other symptoms appear, it’s time to take a trip for some veterinary care. 

Dental Disease

dog getting teeth brushed

Dental disease is another common cause of frothing or excessive drooling. Just as with humans, bacteria in a dog’s mouth can build up and cause infections and other problems with your dog’s teeth. 

They can also cause abscesses which are pockets of pus that create a hole for drainage. Of course, this is uncomfortable for your dog, and it can become a serious health issue. You can tell if your dog’s foaming is due to dental issues if you notice he also has bad breath, problems eating, blood in his water bowl, or any other indications that he has a toothache or pain around his mouth. 

You can prevent most dental health issues if you practice good dental hygiene with your dog. You want to make sure he has good quality dog food, plenty of fresh drinking water, and you’ll want to brush his teeth ideally twice a day, but minimally three times a week

More Serious Causes of Dog Foaming

Many of the common causes of dog foaming we’ve talked about can become serious and require veterinary care. But there are some more serious causes you need to be aware of so you can determine if you need to take a trip to the emergency vet. 

Toxic Substances

what toxins can cause seizures in dogs

As mentioned above, if you suspect your dog got into any kind of toxic substance, it’s time to go to the vet. Go to the emergency vet if it’s during the night or other off-hours, but don’t delay. 

If your dog got into something toxic, minutes count, and excessive drooling is the least of your worries. Aside from getting him to the vet as quickly as possible, you’ll want to contact the Animal Poison Control Center at the ASPCA. They can give you valuable first aid instructions until you can get to an emergency vet. 


Another serious health issue that can cause hypersalivation and dog foaming is seizures. A seizure is like every muscle in your dog’s body contracting at once. It can easily cause drool to foam, and it causes other abnormal behaviors as well. 

Dogs will commonly experience aggressive behavior following a seizure, and so it wouldn’t be unusual to see your dog acting both angrily and frothing at the mouth. It’s not rabies, in this case, it’s a seizure, but it’s a cause for a visit to the emergency vet since it can leave your dog with major health issues. 


how often should dogs get rabies shots

Now for the elephant in the room — could it be rabies? While this serious condition has been highlighted in the movies and you often hear rumors about it, because of the advent of rabies vaccinations, it’s actually very unusual in our modern world. 

It is, however, one possible cause of dog foaming, and you have to consider the possibility if you haven’t gotten your dog a rabies vaccination. That’s why it’s best to avoid an unknown dog if you see that it is frothing at the mouth. 

In that case, you’ll want to contact animal control so they can get the animal the help it needs. If you know that your dog has come into contact with a rabid animal, and he’s now frothing at the mouth, you need to contact your vet for advice on what to do next. 

Of course, the best medicine is prevention, and that means making sure your dog is up-to-date on his rabies vaccination. It’s also important to realize that rabid animals exhibit other symptoms apart from excessive frothing. 

If an animal has rabies, it will also usually have trouble swallowing as well as other nervous system symptoms like erratic behavior or an inability to fully close its mouth. If you see these symptoms in combination with frothing at the mouth in your dog or any animal, it’s best to take proper precautions by contacting your vet or animal control and avoiding any contact with the animal. 

How Do I Know When to Worry?

If your dog is frothing at the mouth for more than a couple of hours, it’s usually best to contact your vet for more advice. If the drooling is caused by something that’s not a serious condition, it should resolve within a few hours or less. 

If your dog’s foaming does not resolve or if it gets worse, it’s time to talk to your vet. If you notice other symptoms accompanying the drooling, that’s another reason to seek veterinary care. 

You don’t want to overlook dog foaming as a sign of another serious health issue, and so, if you have any questions at all, it’s best to just contact your vet to get more advice on what to do. As the saying goes, better safe than sorry, especially when it comes to some of the more serious medical conditions that drooling can indicate. 

Final Thoughts

If you see your dog foaming at the mouth, it doesn’t automatically mean that he has rabies. There are many other reasons he might be experiencing hypersalivation accompanied by heavy breathing which produces froth. 

The most common causes of dog foaming are often not serious, but if it continues for more than a few hours or is accompanied by other symptoms, it’s time to get it checked out. It’s the least you can do for your best furry friend!