Your pet’s immune system is fine-tuned to fight foreign invaders, but sometimes this system can overreact, causing a hypersensitivity reaction. Pets can experience different types of hypersensitivity reactions, such as chronic allergies and autoimmune diseases. One of the most common and easily identified hypersensitivity reactions is an acute allergic reaction, which can cause facial swelling and hives or, in severe cases, shock and collapse. The Colony Veterinary Hospital team wants you to understand allergic reactions, learn to identify the signs, and know what to do if your four-legged friend is affected. 

What causes allergic reactions in pets?

Allergic reactions are caused by the immune system overreacting to a foreign substance. Any substance can theoretically cause a reaction in an individual pet, but the most common culprits are insect bites and stings, medications, and vaccines. Reactions typically happen after the second or third exposure to a substance because the immune system becomes increasingly sensitized over time. 

A cascade of events occur during an allergic reaction which leads to the release of inflammatory chemicals into the bloodstream. These chemicals affect various parts of the body and lead to the signs typically associated with an allergic reaction.

What are the most common signs of allergic reactions in pets?

Allergic reactions range in severity from minor skin swelling around an insect bite to systemic effects such as shock and collapse. Most reactions fall somewhere in the middle of this spectrum, necessitating same-day care but not an immediate emergency visit. These signs include the following:

  • Facial swelling
  • Local swelling around the site of exposure
  • Hives
  • Itching
  • Vomiting or diarrhea

What is the difference between an allergic reaction and anaphylaxis?

Although anaphylaxis rarely occurs, it is the most severe form of allergic reaction. Instead of inflammatory chemicals affecting the skin, they target the cardiovascular system and other internal organs. This causes blood vessels to dilate, blood pressure to drop, and the pet to potentially collapse. Affected pets may also have labored breathing. Unlike typical allergic reactions that develop over several hours, anaphylaxis develops within minutes and can quickly become life-threatening. Treatment requires immediate medical attention to restore normal blood flow and address breathing issues.

What should I do if my pet has an allergic reaction?

A typical allergic reaction can cause your pet discomfort and worsen without treatment. Seek same-day veterinary care with our team or a local emergency facility if you notice allergic reaction signs in your pet. Our skilled team can administer medications to reduce inflammation, itching, swelling, and hives.

If your pet has an allergic reaction that seems especially severe or progresses quickly, or your pet shows anaphylaxis signs, seek emergency care right away. Left untreated, anaphylactic shock can quickly lead to death. An emergency veterinary facility can provide treatment to counteract the hypersensitive response and address life-threatening symptoms. After emergency care is administered, pets experiencing anaphylaxis typically remain hospitalized for 24 hours or longer to monitor their condition and provide continued supportive care.

Can I prevent future reactions in my pet?

Allergic reactions can be challenging to prevent because the cause is not always apparent. In cases where the cause is known, it may be difficult to avoid—such as with bee stings. For pets with known allergies to vaccines, our veterinary team can give reaction-mitigating medications ahead of time or decide whether it is best to avoid the vaccine altogether.

Most allergic reactions are isolated incidences, but some pets may develop repeated reactions that significantly impact their quality of life. These pets usually have other chronic allergic conditions and may already be receiving treatment for them. A visit to a veterinary dermatologist for allergy testing and desensitization therapy (i.e., allergy shots) may help to identify the problem substances, reduce reaction intensity, and provide pet owners with treatments they can administer at home.

You may feel scared or overwhelmed when your pet has an allergic reaction, but we hope this guide will help you know how to respond. Contact Colony Veterinary Hospital for immediate care if your pet has an allergic reaction during our normal business hours. If your pet has an urgent after-hours situation, contact your nearest veterinary emergency facility for same-day care.