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Anaphylactic Shock in Dogs: Symptoms, Causes, and What to Do

A dog lays on its side outside on a wooden deck

Dr. Erica Irish author of Anaphylactic Shock in Dogs: Symptoms, Causes, and What to Do

Dogs can develop the same types of allergies that people can develop. When having an allergic reaction, some of the signs can be mild. Severe clinical signs associated with an allergic reaction can be life-threatening, and your pup can go into anaphylactic shock if left untreated.

What is anaphylactic shock?

The termanaphylaxis refers to the acute onset of an allergic reaction due to exposure to foreign material. In order for an allergic reaction of this nature to occur, there needs to be prior exposure to the material. The immune system’s initial response to the foreign material is to produce antibodies that bind to the surface ofmast cells. Mast cells have several jobs, including protection against harmful pathogens.

When a dog is exposed to the same foreign material a second time, the mast cells that are coated with antibodies will recognize the material and attack it, releasing inflammatory mediators such as histamines. This is the cause of the redness and hives that can develop after exposure to an allergen, for example.

Like in the case of allergies, the immune system often overreacts when it comes to exposure to certain things. Hives and swelling are an indicator of mild anaphylaxis. However, severe anaphylaxis is possible in some cases. Severe anaphylaxis affects many other parts of the body, and when it causes trouble breathing or circulatory problems, this is referred to as anaphylactic shock.   

What can cause anaphylactic shock in dogs?

Dogs can develop allergies to almost anything. Environmental allergens are some of the most common causes and are particularly prevalent in the Southern states where there is warmer weather for longer parts of the year. Grasses, weeds, trees, pollen, and dust are all examples of environmental allergens. Mild skin and respiratory problems can develop from exposure, but trouble breathing means that a dog might be having severe anaphylaxis.  

Insect bites can also cause allergic reactions. This is common with mosquito bites and sometimes bites from fleas. Severe anaphylaxis from exposure to fleas is rare but possible. Spider bites and snake bites are more likely to cause moderate to severe anaphylaxis.

Food protein can also cause anaphylaxis. In fact, if your dog has a true food allergy, he is more likely allergic to the protein in the food rather than the grain or any other ingredient. Dogs can also develop anaphylaxis due to vaccinations and medications.

Signs of anaphylactic shock in dogs

Most dogs with mild to moderate anaphylaxis will experience signs based on their exposure. For dogs with food allergies, they can develop skin and ear infections as well as vomiting and diarrhea. They can develop hives or swell at the site of the exposure. Respiratory allergens are more likely to cause sneezing.

Severe anaphylaxis can cause difficulty breathing, excessive drooling, and pale to bluish-colored gums. Your pup may seem very weak and might collapse. In extreme cases, seizures are also possible.

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What to do if your dog has anaphylaxis

If your dog is experiencing any of these clinical signs, it is best to contact your veterinarian right away. Hives and swelling should be seen on the same day that they develop, but difficulty breathing, pale gums, and collapse are all reasons that your dog should be seen as an emergency.

Mild anaphylaxis can be treated with antihistamines, and in some cases, a corticosteroid is recommended. For moderate to severe anaphylaxis, your pup may need supplemental oxygen and intravenous fluids to help stabilize him. There are also injectable medications to help the heart like epinephrine and atropine, and bronchodilator medications may be utilized to help open up your dog’s airways.

It will help to think about your pup’s possible exposures. If he just received vaccines recently, that could explain why there are hives or a localized swelling over the injection site. Extreme facial or limb swelling could mean that your dog was stung by an insect or bitten by a snake. If recurring skin and/or ear infections are part of the issue, then your dog will need a medical work-up to rule out environmental and food and flea allergies.

How to prevent anaphylaxis

If it all possible, it is best to avoid the allergens that cause your dog’s anaphylaxis. For dogs with mild anaphylaxis to vaccinations, it is okay to continue giving them annually as long as you give an injectable antihistamine a few minutes prior to the vaccine. For dogs with severe anaphylaxis due to vaccines, your vet may recommend that you skip all future vaccinations.

Dogs with food allergies tend to benefit from novel protein or hydrolyzed protein diets, and a food elimination trial is necessary to determine the exact cause of your dog’s food allergy. Food allergy “tests” that rely on blood, hair, and/or saliva samples for diagnosis are not reliable.

Environmental allergies may be more difficult to avoid if they are endemic in your area. Intradermal skin testing for allergies can be performed to determine the worst allergens and then are used in the form of immunotherapy. This is like a vaccine for your dog and it “reboots” the immune system so that future allergic reactions are much less extreme. Antihistamines, topical medications, shampoos, and anti-itch medications like Apoquel can all help mitigate clinical signs from skin and ear allergies.


Anaphylaxis can affect almost any dog, and the response can vary from mild to severe. In cases of severe anaphylaxis, your pup can go into shock. This is a medical emergency and means that you should contact your veterinarian right away. Anaphylactic shock can be fatal if left untreated.  

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Meet The Author 

Dr. Erica Irish author of Anaphylactic Shock in Dogs: Symptoms, Causes, and What to Do

Dr. Erica Irish

Erica has worked in the veterinary field since 2006, starting out as a veterinary technician before graduating from the UF College of Veterinary Medicine in 2013. As a general practitioner in an animal hospital, she has many interests and is especially interested in dermatology, cardiology, internal and integrative medicine.

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