Anaphylaxis in Dogs

Published Sep. 30, 2022

In This Article


What Is Anaphylaxis in Dogs?

The immune system serves an important role in protecting your dog from infections and other microscopic threats; however, it can often be overstimulated and result in hypersensitivities or allergies.

Hypersensitivities can be mild or severe and can be local or involve the entire body (systemic). Severe, systemic hypersensitivities are commonly referred to as anaphylaxis, or anaphylactic shock.

Though rare, if anaphylaxis occurs in a dog, it is a medical emergency. If you think your dog is experiencing anaphylaxis, contact your nearest emergency veterinary office.

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Symptoms of Anaphylaxis in Dogs

Anaphylaxis occurs because of the inappropriate release of certain infection-fighting compounds by white blood cells. The most common compound released is histamine. In smaller doses histamine causes hives and itching, but when released in large amounts it dilates blood vessels, increases heart rate, and causes low blood pressure.

In most species, anaphylaxis primarily affects the lungs and airways; however, in dogs the gastrointestinal tract often releases histamine directly into the liver, causing symptoms such as vomiting and diarrhea as well as liver enzyme elevations to be more commonly seen.

Severe vomiting, diarrhea, and lethargy may occur suddenly and appear to come out of nowhere. If allowed to progress, this can lead to collapse, convulsions, and even death.

Other symptoms of anaphylaxis in dogs include facial swelling, itching, and hives, which may or may not progress to difficulty in breathing. Though these effects are more likely to occur in less severe cases of hypersensitivity, they still warrant prompt evaluation by a veterinarian.

Causes of Anaphylaxis in Dogs

In theory, any foreign molecule can trigger an anaphylactic reaction, though a dog must have been exposed to this trigger at least twice before shock can occur.

Most canine reactions are to insect bites or stings (commonly bees, wasps, and venomous ants), medications, antigens in vaccines, or chemicals. Anaphylaxis related to food proteins is very rare, though it has been documented.

How Veterinarians Diagnose Anaphylaxis in Dogs

Diagnosis of anaphylactic shock is usually based on clinical signs, physical exam, and history of exposure to an allergen (if the allergy is known).

Blood tests may help confirm the diagnosis by demonstrating dehydration or liver enzyme elevations, though these tests can also be normal. Inflammation of the liver and gallbladder may be seen on an abdominal ultrasound. 

Treatment of Anaphylaxis in Dogs

Anaphylaxis is a medical emergency, and immediate attention is essential to survival. Your vet will use a combination of medications to reduce the immune response and counteract the symptoms. Epinephrine and corticosteroids such as dexamethasone are commonly used for this purpose.

If a dog has progressed to anaphylactic shock, intravenous fluids may be needed to maintain blood pressure. Severe airway swelling may require a breathing tube, sedation, and even ventilation to ensure your pet can breathe. 

Recovery and Management of Anaphylaxis in Dogs

Prognosis will depend on the severity of the reaction and how quickly care is managed. Mild cases may respond to treatment without hospitalization, while aggressively treated animals may still succumb to a particularly severe reaction.

Histamine released in the system works rapidly and if the effects of this compound aren’t counteracted by medications and support very quickly, the decreased blood pressure can give the body further signals to shut down, and these are harder to combat. In the hospital, severely affected patients are usually observed and treated for at least 2-3 days to make sure that no delayed effects are noted.

Anaphylactic and allergic reactions worsen with repeat exposures, so allergy testing may be worthwhile in recovered dogs who experienced severe symptoms. Avoidance of the allergen, if possible, is best. For allergens that are difficult to avoid, discuss an emergency plan with your veterinarian. This may include medications such as steroids or an Epi-pen that can be kept at home for immediate use.


Featured Image:ław Iciak

Jamie Lovejoy, DVM


Jamie Lovejoy, DVM


Dr. Jamie Lovejoy graduated from Tufts Cummings School of Veterinary Medicine in 2012 after an undergraduate degree in Marine Biology. ...

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