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Dog Runny Nose: What Causes Nasal Discharge and Congestion?

It’s common for dogs to have a runny nose with clear discharge. An occasional runny nose without other symptoms is often a sign of a minor issue, such as cold weather or a mild allergy.

Coloured nasal discharge can be a more serious symptom though. For example, yellow, green, or cloudy discharge could indicate an infection or disease. A runny nose combined with other symptoms is also a cause for concern.

Additionally, a continuous or regular runny nose shouldn’t be ignored. Dogs rely on their sense of smell, so anything that affects this could impact their quality of life.

Let’s take a closer look at the potential causes of a runny nose in dogs. We’ll also discuss how to prevent a runny nose and when to contact a vet.

7 Causes of a Runny Nose in Dogs

Dog Runny Nose: What Causes Nasal Discharge and Congestion?

A runny nose is often caused by the nasal passages becoming irritated or dry. This triggers the dog’s nasal glands to produce more mucus to protect the nasal lining.

There are many underlying reasons for an irritated nasal passage, ranging from mild to serious. The right treatment depends on what’s causing the issue, so you should always contact a vet if you notice symptoms of illness, a continuously runny nose, or a coloured discharge.

1. Allergies

Allergies are the most common cause of clear nasal discharge in dogs. Allergens trigger inflammation in the nasal passage, which causes the discharge to be produced.

Many allergens can cause nasal discharge. This can make it hard to identify the one triggering your dog’s symptoms, although there are a few ways to narrow it down.

In most cases, a runny nose is caused by airborne allergens, which enter the nose directly. Some examples include dander, dust mites, pollen and moulds. Allergies to food and medication can also cause a runny nose though.

You can narrow down potential allergens further by noticing when your dog’s allergies are worst. If they are seasonal, then pollen might be the trigger. But if the symptoms are year-round, then food, mould, or dust mites are more likely culprits.

Allergies rarely cause just a runny nose. There are almost always other symptoms, such as:

  • Coughing
  • Wheezing or difficulty breathing
  • Sneezing
  • Nosebleeds
  • Watery eyes
  • Sore ears
  • Itching
  • Paw licking

The best way to treat allergies is to minimise your dog’s exposure to the allergen. This can be difficult, especially if you don’t know what’s triggering the symptoms.

For this reason, it’s important to visit a vet if you notice signs of an allergy. They might recommend treatments such as antihistamines or an allergy test.

2. Infections

Infections are another common cause of a runny nose in dogs. But unlike allergies, the discharge due to infection is usually thick or coloured.

Other symptoms of an infection include:

  • Coughing
  • Odorous discharge
  • Mucus build-up

Bacterial, viral, and fungal infections can all cause a runny nose. Even certain types of parasites, such as nasal mites, can lead to nasal discharge.

For this reason, you must visit a vet if you notice any of the above symptoms. The right treatment depends on the type of infection, so an accurate diagnosis is essential.

3. Item Stuck In The Nasal Passage

A dog’s nose spends a lot of time sniffing close to the floor. This can sometimes cause small objects to get stuck inside the nose.

Any foreign bodies lodged inside the nose can cause irritation and nasal discharge. The symptoms often affect just one nostril, unlike infections or allergies.

Some examples of objects that can get stuck inside a dog’s nose include grass seeds, blades of grass, small insects, flower petals or gravel.

A dog with a foreign object stuck in their nose will often shake their head or paw at the nose. They may also sneeze a lot or suffer from nosebleeds.

If you can see the object, you might be able to remove it carefully with tweezers. But it’s usually safer to visit a vet, as the lining of the nose is very sensitive and prone to bleeding.

4. Airborne Irritants

Irritants in the air can cause the nose lining to become inflamed. The nose glands will then produce mucus to remove the irritant.

Some of the most common examples of airborne irritants include:

  • Excessive dust
  • Cigarette smoke
  • Cleaning products
  • Candles or incense

Unlike allergies, there’s no medication that can reduce the symptoms of an airborne irritant. Instead, you’ll need to improve your home’s air quality.

Note: Cold weather may also trigger a runny nose. The air causes the nasal lining to dry out, which increases mucus production.

5. Periodontal Disease

Periodontal disease is caused by plaque and tartar build-up on the dog’s gums and teeth. It can lead to various symptoms, including an ongoing runny nose.

In many cases, the nasal discharge caused by periodontal disease will only come from one nostril. The discharge will also typically be thicker than with allergies.

Other symptoms of periodontal disease include a loss of appetite, pawing at the mouth, and pain when eating.

Periodontal disease is a serious condition that needs veterinary care. You should always contact a vet if you notice these symptoms.

6. Distemper

Distemper is a virus that attacks many organs of a dog’s body, ranging from the gut to the brain. This means it can cause many symptoms, such as a loss of appetite, diarrhoea, fits, and even death.

It can also cause a continuously runny nose, which typically becomes more sticky and pus-like over time.

The best way to prevent distemper is through vaccination. It’s an airborne virus that can be picked up through contact with other dogs (or items they have touched), so vaccination is essential to protect your pet.

You should contact a vet immediately if your dog shows symptoms of distemper (particularly if they haven’t had a distemper vaccination). It’s a very serious condition that’s fatal in many cases, so your dog will require medical care to give them the best chance of overcoming the virus.

7. Nasal Polyps or Tumours

Nasal polyps are growths inside the nasal cavity. They can cause irritation and a continuous runny nose (also known as a nasal drip).

Polyps may also restrict the airflow through your dog’s nose and make breathing difficult. Surgery is usually required to remove them, although they may grow back in the future.

While nasal polyps usually aren’t harmful, similar symptoms can also be caused by tumours in the nose. Both benign and cancerous tumours can lead to a nasal drip, which is why getting a vet checkup is essential.

When Should You Visit a Vet?

A clear and watery nasal discharge usually isn’t anything to worry about.

However, this only applies if the clear runny nose is occasional and there are no other symptoms (such as loss of appetite or coughing). An ongoing runny nose, or a discharge that isn’t clear and watery, could indicate a medical issue.

For this reason, you should always contact a vet if you have concerns about your dog’s runny nose. This is especially important if:

  • The runny nose is combined with other symptoms (including behaviour changes)
  • The discharge continues for more than a short period or becomes chronic
  • The discharge happens regularly
  • The discharge is cloudy, green, yellow, or any colour other than clear
  • The discharge is thick, rather than thin and watery
  • The discharge has a noticeable odor
  • You have doubts about your dog’s health or wellbeing

Related Questions About Runny Noses in Dogs

Are Certain Breeds More Prone to Nasal Discharge?

Any dog can suffer from a runny nose, but brachycephalic breeds are often more prone to it. These breeds have weak cartilage inside the nose and often have difficulty breathing, making a runny nose more likely.

What Can You Give A Dog for a Runny Nose?

Treatment for a runny nose in dogs depends on the underlying cause. For allergies, a vet may recommend antihistamines or an allergy test. For bacterial infections, a course of antibiotics may be required. 

You should never give your dog medication or treatment without discussing it with your vet. The wrong treatment could cause additional health problems.


There are many potential causes of a runny nose in dogs. These range from relatively mild issues, such as allergies, to life-threatening conditions such as distemper.

A clear, watery, odourless nasal discharge is often not a worrying sign – as long as it only happens occasionally. But you should contact a vet if you notice other symptoms, if the runny nose happens a lot, if the discharge is coloured, or if it has an odour.

Do you have any questions about what causes a dog to have a runny nose? Please let us know in the comments below.

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About The Author: Richard Cross

Richard is a journalist who specialises in dog behavior. He's written hundreds of articles and books related to dogs, including for the Continental Kennel Club, Dog Fest (the UK's biggest dog festival) and various veterinary surgeries. When he's not spending time with Jess and Rudy (his beloved Labrador and Golden Retrievers), he enjoys reading, hiking and watching sports. You can find him on Facebook or Twitter.

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