Anaphylaxis in Dogs

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Anaphylaxis is the sudden reaction of the body when it's exposed to a foreign substance to which it has developed antibodies. It's a hypersensitivity reaction, which means that the response is an overreaction of the immune system to the allergen.

An anaphylactic reaction can be localized to one are of the body, such as the skin, or it can be widespread and systemic, in which case it's referred to as anaphylactic shock.

What Causes an Anaphylactic Reaction in a Dog?

At some point before the anaphylaxis, the dog must have been exposed to the allergen already. When that happened, the body responded by producing IgE, which is antibody to the allergen. The IgE binds to mast cells, which are part of the immune system. This first exposure to the allergen causes a small, local reaction, such as an itchy, sore red bump at the site of a bee sting.

This sensitization and the subsequent anaphylactic reactions are an abnormal over-reaction of the immune system.

The next time the dog is exposed to that same allergen, the mast cells recognize it and release their contents in response (histamine is one content of mast cells) and that's called degranulation and activation of the mast cells. It can cause extreme swelling and redness (an allergic reaction) around a large area.

Sometimes, the initial mast cell response can trigger a chain reaction of mast cells throughout the dog's body, and that leads to the dangerous condition of anaphylactic shock.

Any substance that is foreign to the body can create an anaphylactic reaction. The most common substances to do so include:

• Food proteins
• Insect bites (spiders and bees most commonly)
• Vaccines
• Chemicals
• Medications

Signs of Anaphylaxis in Dogs

Signs of anaphylaxis in dogs depends on how the foreign substance gets into the dog and how sensitive the immune system is to that allergen. Signs can include:

• Vomiting and diarrhea
• Extreme drooling
• Hives (red swellings on the skin)
• Swollen face or muzzle
• Extreme itchiness
• Blue mucous membranes *
• Difficulty breathing *
• Collapse *

* During anaphylactic shock. This is an emergency.

A reaction that begins as localized can progress to systemic (shock) in some cases, so even localized reactions should be treated as medical emergencies. Treatment should be sought immediately.

Diagnosing Canine Anaphylaxis

Anaphylaxis is diagnosed through physical exam and a history of exposure to some sort of allergen. Skin and blood testing can be done to identify specific allergens when a dog is suspected to have allergies.

Treatment of Anaphylaxis in Dogs

Mild cases of anaphylaxis may be treated with corticosteroids to decrease the immune system's activity and antihistamines like Benadryl to combat the histamine the mast cells are releasing.

More serious cases, like those involving widespread hives, a swollen muzzle, or difficulty breathing, require hospitalization and aggressive treatment with oxygen, IV fluids, epinephrine, atropine, aminophylline, and other medications as necessary. The emergency medications are meant to counteract circulatory collapse and stop the reaction.

It's crucial to understand that each reaction is bigger than the last when it comes to anaphylaxis, so the inciting foreign substance should be identified if possible and avoided in the future.

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