Severe allergic reactions in dogs

isolated dog


Just like people, it is possible for a dog to have an allergic reaction to something such as a bee sting, a medication, or a vaccine.

Most allergic reactions improve quickly with treatment from your vet, but occasionally they can be life threatening. Serious allergic reactions (anaphylaxis) can be deadly and require a rapid response.


Contact your vet immediately if your dog begins to show signs of an allergic reaction.

This article does not cover chronic allergies such as food allergies, flea allergies or pollen allergies (atopic dermatitis). Separate articles with information on these conditions are available.

When to contact your vet

Symptoms of an allergic reaction (listed below) can start suddenly and without warning. A dog showing symptoms of a severe allergic reaction needs emergency, lifesaving veterinary treatment.

You know your dog best. Contact your vet if you’re concerned.


  • Skin rash, swellings or hives (bumps)
  • Swollen face (or swelling elsewhere on the body)
  • Itchy skin.

A severe allergic reaction (anaphylaxis) may also cause:

  • Breathing difficulties
  • Cold ears, legs and feet
  • A pounding heart beat
  • Vomiting and/or diarrhoea
  • Collapse
  • Coma or death.

Symptoms vary depending on what your dog has reacted to and how severe their reaction is. Anaphylaxis is the same kind of life-threatening reaction that humans with peanut allergies suffer.

dog allergic reaction after bee sting

This dog is having an allergic reaction after a bee sting.


Allergic reactions are caused by the body overreacting to something it’s sensitive to. A first reaction is usually quite mild, but each reaction after that is likely to get worse. Occasionally a first reaction is severe and happens without warning.

Common allergies include:

  • Medicines (such as vaccines, flea medicines and antibiotics)
  • Bee stings, wasp stings and insect bites
  • Chemicals (cleaners and air fresheners)
  • Plants (nettles).

However, it’s possible for a dog to be allergic to just about anything.


Treatment depends on how severe the reaction is. If you dog has a mild reaction, they’re likely to be discharged after being given medication to reduce swelling and settle their symptoms.

If your dog has a more severe reaction, it’s likely they’ll be admitted into the veterinary hospital for intensive treatment. This could include a drip to give fluids, medication directly into the vein and, if your dog is having trouble breathing, they may need a tube placed into their windpipe to supply oxygen.

Published: February 2019

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Written by vets and vet nurses. This advice is for UK pets only.

Illustrations by Samantha Elmhurst