Dog Allergic Reaction – How To Tell If Your Dog Is Allergic To Something?

  • Home
  • /
  • Blog
  • /
  • Dog Allergy
  • /
  • Dog Allergic Reaction – How To Tell If Your Dog Is Allergic To Something?


A devoted pet parent, pet store manager and animal shelter volunteer. Read more about me here.

Believe it or not, dogs can have allergies just like humans can.

Dog allergies are various, and they can come in at the most inconvenient times.

It should go without saying - but it bears repeating - you need to be careful about new things around your dog. Surprisingly, your pup could be allergic to something!

That being said, how can you tell if the issue at hand is a dog allergic reaction? What signs should you be looking for?

Continue reading to find out everything about dog allergic reactions!

What Is A Dog Allergy?

A dog having its ears checked out at the vet

Commonly speaking, dogs can be irritated by everything and anything from their environment, just like humans and other animals. Dogs usually get allergies because they inherit the genes for allergies from their parents. In a way, that means that dog allergies are impossible to avoid - because there is nothing you can do about it.

However, some dog breeds are prone to developing allergies more than other breeds. Those breeds would have to be Lhasa Apsos, Bulldogs, Retrievers, Shar-Peis, Terriers, and Shih Tzus. That of course, doesn’t mean that other breeds cannot get allergies - they can.

The truth is, most allergies appear when your dog is still young - between a few months of age and 3 years of age. After a while, you can notice that your dog is reacting seasonally, or that certain things make their allergies worse.

How does an allergy happen in the first place?

An allergic reaction is, simply said - overactivity of the immune system, or hypersensitivity to a certain substance, in this case, called an allergen. Commonly, allergens consist of plant protein, insects, foods, or animals. 

When a dog is exposed to an allergen from time to time (or often),  these conditions can make the immune system sensitive to the allergen in question. Over time, that can cause an over-reaction of the immune system, although the body worked just fine and didn’t mind the allergen from the start.

At some point, the immune system can create a response that can be harmful to the dog’s body. Generally, the immune system of all living beings exists to protect from viral or bacterial infections, or disease. However, when the body reacts to allergen, it means that the body is trying to fight off a benign substance, making the reaction rather harmful to the body.

Dog allergic reaction is a rather complex process because of the immune response. It can be summed up like this:

  • The allergen protein molecules mix with the antibodies found in the blood.
  • Once they mix, the allergen protein will attach to a mast cell - a type of cell, found in various tissues across the entire body.
  • When the antigen and the antibody interact with a mast cell, the mast cell will release a potent chemical. That potent chemical is usually histamine - which causes local inflammation in the body.
  • The local inflammation appears like swelling, redness, and itching on the skin. However, the inflammation can cause more serious symptoms of the dog allergic reaction, but more on that later.

Types Of Allergic Reactions In Dogs

An old dog getting examined by a vet

In reality, there are a few different allergic reactions in dogs. We will talk about them starting with the non-life-threatening ones, and finish with those that can be fatal. So, let’s start!

Skin Allergic Reaction

Skin allergies usually appear as a skin condition. Skin allergies are generally caused by exposure to a certain element like fleas, ticks, some plants, or yard chemicals - but even food can cause skin allergic reactions. These allergies cause an allergic reaction called an atopic allergy, but they can also cause dermatitis.

The element irritates the skin, causing an allergic reaction. The most common symptom of a skin allergic reaction is redness, even some hives - red bumps on one area or the entire body. 

Other, less common causes for an allergic reaction on the skin is a new detergent or a dog shampoo. Resolving the allergic reaction is simply done by removing the allergen from your dog’s environment. Also, consider putting your dog on a flea & tick preventive!

Edema Of The Face And Throat

Edema is another term for the swelling of the face and throat. This is the next step of severity in the term of allergic reactions. 

Generally, having edema of the face is a good sign, because the dog is not likely to get a fatal reaction to the allergen. The edema will likely occur in 30 minutes to a few hours after the exposure. If left untreated, the swelling should go down within a 2-day window, but we still recommend that you go to the vet and get an antihistamine injection.


Hives are an allergic reaction that commonly appears in a few hours to a full day after exposure. Hives are also called urticaria, and this reaction consists of extreme itchiness and red bumps on the skin.

The hives can be difficult to spot if you have a long-haired dog. If you do, and you are worried about a potential allergic reaction - try to feel their body for bumps. See the vet if your pup has a hives breakout to get an antihistamine treatment.

Anaphylactic Shock

Anaphylaxis is the scariest and the most dangerous immune response to an allergen. Most often, dogs respond strongly to certain allergens - like the insect bite or medication and vaccines they are allergic to.

The poor pup’s body produces antibodies, which react with the allergen. That process can drop blood pressure a lot, and send the body into anaphylactic shock.

If your dog ever experienced anaphylaxis before, we recommend that you carry an epi-pen with you at all times. Luckily, anaphylaxis is very rare in pups, but you should still be on the lookout if your pup is taking new medication.

Allergic Reaction Symptoms

An old dog being examined by a vet

Not all allergic reactions look the same - the allergy can cause different symptoms in different dogs. Also, different allergens can cause different reactions from your dog’s immune system. But, what does a dog allergy look like?

The allergy can affect one area or several areas of the body, and every time your dog gets an allergic reaction, it could be different than last time. So, let’s get into it!


When your dog is itchy and scratching excessively, he might have an allergic reaction to something. The scratching is usually followed by a breakout of hives all over the body or concentrated in one area.

Hives and itchiness are the most common allergic reactions of all. Do note that these reactions are the mildest, so if there are no other symptoms present, you don’t have to visit the vet immediately, but you should do it in the next couple of days.

What you can do from home is give your pup some Benadryl to calm down the breakout and stop the itching. If you aren’t sure about the exact dosage of Benadryl for your pup, call your local vet to help you.

Tummy Woes

If your dog is experiencing tummy woes, it could be an allergic reaction to something your poor pup ate. The most common woes are diarrhea, vomiting, and an upset tummy. 

The truth is, if your pup seems to be very uncomfortable or dehydrated, it’s best to visit the vet as soon as possible. The early anaphylactic reaction looks like tummy woes, so you need to be careful!

Itchy Ears

Seeing your furry baby scratching at his ears can be a sign that he is exposed to an allergen. However, itchy ears are rarely dangerous or life-threatening, so it can wait for the next vet visit to mention.

Do note that if the itchy ears are accompanied by other symptoms, visit the vet. Those symptoms commonly are lethargy, titled head, or trouble walking - so if you see those, go to the emergency vet clinic!

Runny Nose & Sneezing

When sneezing or the runny nose are accompanied by other symptoms, the pup needs to be seen by a vet. If your pup is sneezing and is running a fever, it’s time for a vet visit.

Generally speaking, runny nose or sneezing are symptoms of seasonal allergies. Seasonal allergies are very benign, but your vet still needs to rule out other causes before they make the diagnosis.

Runny Eyes

Runny eyes as a symptom by itself are a benign allergic reaction. However, serious respiratory infections are first manifested by runny eyes.

Meaning, if your dog has come down with a dangerous respiratory infection, runny eyes could be the early sign. If that is the case, the pup could come down with some damage to the eye - like a scratch or the cornea ulceration. Take your dog to the vet to be safe.

Skin Chewing & Licking

If you can spot your pet chewing and licking on his skin, commonly his feet - it could be due to an immune response. Usually, that is the sign that your pup is irritated by something in your yard or on the daily walks to the park. 

Do note that it could be a sign of food allergies as well. The skin chewing or licking itself is not dangerous, but you should schedule a visit to the vet just to be safe.

Swollen Face & Throat

When your pup comes down with some swelling on his face, that’s almost a sure sign that the pup got an acute allergy from a bite or a sting of an insect. Another potential cause is that your pup breathed in a certain allergen, like pollen or something similar. 

If you do spot the swelling on the throat of your dog, be very careful about the things you do next. Swelling on the throat could be a sign that your pup could get into anaphylactic shock. Swelling on the face is less likely to become fatal, but you should nevertheless see a vet for your pup.

Our official recommendation is that if you see that your dog has a case of a swollen face and throat that you take him to the vet immediately. The vet will give your dog the right treatment and prevent the allergy from becoming worse.

Dog Allergic Reaction - Bottom Line

To conclude, there are a few tell-tale signs that your dog is having an allergic reaction to something from his surroundings. Whatever happens - be careful that it doesn’t happen again.

Dogs rarely get a strong allergic reaction, but that doesn’t mean that they can’t go into anaphylactic shock. Be wary of your pet’s allergies and keep him safe!

Loved the article?
Learned Something New & Interesting?
Share it with your people so they (& their doggos) can enjoy the benefits too!

About the Author

A devoted pet parent to two lovely creatures – Charlie the Cat and Jimmy the Dog – a full-time assistant pet store manager, and an animal shelter volunteer. I've gathered knowledge about pets for almost a decade, and it all started in a small store called Jack's Pets.

{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}