Allergic reactions in dogs


  • Dogs can be allergic to almost anything but some of the most common triggers include insect venom, snake venom and certain medications.
  • Allergic reactions can be very serious, and sometimes life threatening. Contact your vet immediately if your dog is having an allergic reaction.
  • Fortunately, most allergic reactions can be treated successfully if they are caught early.

General information

It's possible for a dog to be allergic to just about anything. Some of the most common triggers include insect venom, snake venom and medications. If your dog has an allergy, their first reaction may be mild, but each reaction afterwards is likely to be progressively worse. However, this rule doesn’t always apply and first reactions can occasionally be severe. This article doesn't include information about chronic (long-term) allergies such as allergic skin disease.


Mild allergic reactions often cause symptoms such as:

  • Itchy skin
  • A rash
  • A swollen face (especially around the ears, eyes, mouth and paws)

Severe allergic reactions/anaphylaxis (the same kind of life-threatening reaction that humans with peanut allergies suffer), cause severe symptoms, such as:



dog allergic reaction after bee sting

This dog has been stung by a bee

When to contact your vet

If your dog is showing signs of an allergic reaction, contact your vet immediately. Never wait to see if their symptoms improve.


Your dog’s treatment will depend on how severe their symptoms are. If your dog is having a mild reaction, it’s likely that they will be given some medication (often steroids, and anti-histamines) before being sent home for monitoring. If your dog is having a more severe reaction, they are likely to need intensive, potentially lifesaving treatment such as assistance breathing, medication directly into their blood stream and a fluid drip.

Consider insuring your dog as soon as you get them, before any signs of illness start. This will ensure you have all the support you need to care for them.

Types of reaction

Bee stings

Most dogs stung by a bee, or another insect, develop redness, pain, and swelling around the site, but recover well (on their own, or with the help of an antihistamine medication). However, just like us, some dogs are allergic to insect stings and suffer much more serious symptoms. Call your vet for advice if an insect has stung your dog.

Medication and vaccine reactions

Although it’s extremely rare, just like us, some dogs are allergic to certain medicines and vaccinations. Fortunately, most medication and vaccination reactions are mild, for example developing itchy skin after a flea treatment, or feeling slightly ‘off-colour’ after a vaccination. However, severe reactions do sometimes happen and cause serious symptoms that require immediate veterinary attention.

Fleas, food, pollen and other allergic skin disease

Allergic skin disease (often caused by fleas, food and/or pollen) is a different type of allergy that causes a low-level, ongoing problem, (not a sudden, acute reaction). Follow the link for more information.

Published: August 2020

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