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Anaphylaxis in Dogs

What Is Anaphylaxis in Dogs?

The immune system plays a crucial role in safeguarding your dog against infections and other microscopic threats. However, there are instances where it can become overly reactive, leading to hypersensitivities or allergies.

Hypersensitivities can vary in intensity, ranging from mild to severe, and may affect specific areas or involve the entire body (systemic). Severe systemic hypersensitivities are often termed as anaphylaxis or anaphylactic shock.

Although rare, if anaphylaxis occurs in a dog, it constitutes a medical emergency. If you suspect your dog is undergoing anaphylaxis, promptly contact your nearest emergency veterinary office.


Anaphylaxis arises due to the inappropriate release of certain infection-fighting compounds by white blood cells, with histamine being the most common. While small doses of histamine result in hives and itching, larger amounts lead to blood vessel dilation, increased heart rate, and low blood pressure.

In many species, anaphylaxis primarily impacts the lungs and airways; however, in dogs, the gastrointestinal tract often releases histamine directly into the liver, manifesting symptoms like vomiting, diarrhea, and elevated liver enzymes more frequently. Severe bouts of vomiting, diarrhea, and lethargy can emerge suddenly and seemingly without warning. Left unchecked, these symptoms can progress to collapse, seizures, and even fatality.

Facial swelling, itching, and hives are among the other indicators of anaphylaxis in dogs, which may or may not advance to breathing difficulties. Although these manifestations are more common in milder cases of hypersensitivity, they necessitate swift assessment by a veterinarian.


In principle, any foreign substance can instigate an anaphylactic response, but a dog must have encountered this trigger at least twice before shock can manifest.

The majority of canine reactions stem from insect bites or stings (typically bees, wasps, and venomous ants), medications, antigens in vaccines, or chemicals. While anaphylaxis linked to food proteins is exceedingly uncommon, documented cases do exist.


The diagnosis of anaphylactic shock typically relies on clinical signs, physical examination findings, and the history of exposure to an allergen (if known).

Blood tests may aid in confirming the diagnosis by revealing signs of dehydration or elevated liver enzymes, although these tests may also yield normal results. Inflammation of the liver and gallbladder may be detected through abdominal ultrasound imaging.


Anaphylaxis represents a medical emergency, and swift attention is crucial for survival. Your veterinarian will employ a blend of medications to diminish the immune response and alleviate symptoms. Epinephrine and corticosteroids like dexamethasone are frequently administered for this objective.

In cases where a dog has advanced to anaphylactic shock, intravenous fluids may be necessary to sustain blood pressure. Pronounced swelling of the airways might necessitate a breathing tube, sedation, and possibly ventilation to ensure your pet can breathe adequately.

Living and Management

The prognosis hinges on the severity of the reaction and the promptness of care. Mild cases may respond well to treatment without requiring hospitalization, but even with aggressive treatment, animals may succumb to extremely severe reactions.

Histamine released into the system acts swiftly, and if its effects aren’t swiftly counteracted by medications and support, the drop in blood pressure can trigger further shutdown signals in the body, which are challenging to reverse. In hospitals, severely affected patients are typically monitored and treated for a minimum of 2-3 days to ensure that no delayed effects arise.

Anaphylactic and allergic reactions exacerbate with repeated exposures, so allergy testing may be beneficial for recovered dogs that endured severe symptoms. Whenever feasible, avoiding the allergen is advisable. For allergens that are hard to evade, discussing an emergency plan with your veterinarian is important. This plan may involve medications like steroids or an Epi-pen that can be kept at home for immediate use.

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