Spotting a dog allergic reaction and what to do

Updated 28/11/2023

Just like us pet parents, dogs can have allergic reactions. Although some of these can be mild allergic reactions, there are times when an allergy could become life-threatening. Because of this, it’s very important to recognize the signs of a dog's allergic reaction.

There are some clear rules on what a dog can and can’t eat, however, allergies can sometimes occur without pet parents realizing. Here’s how to spot if your dog is allergic to something, what to do if you think your pup is showing symptoms of an allergic reaction, and how to prepare for future dog allergic reaction episodes.

Understanding what a dog's allergic reaction is

The VCA Animal Hospital - a verified nationwide collection of veterinary surgeons and experts - defines a dog allergic reaction as ‘[...] a state of over-reactivity or hypersensitivity of the immune system to a particular substance called an allergen.’ There are multiple factors influencing whether a dog will develop an allergy, which could include, family history (genetics), changes to the immune system or exposure to new allergens later in life. Most allergens are proteins from plants, insects, animals, or foods.

Over time, dogs with mild allergies that may initially go unnoticed, can become more severe with repeated exposure and develop into a serious allergic reaction, so knowing the symptoms is key to preventing serious illness.

Signs of an allergic reaction in dogs

Allergic reactions in dogs will vary from pup to pup, but here are some of the key signs of an allergic reaction to look out for:

• Itchiness
• Skin hives
• Facial swelling - face, ears, lips, eyelids, or earflaps
• Red, inflamed skin
• Diarrhea
• Vomiting
• Sneezing
• Itchy ears
• Chronic ear infections
• Itchy, runny eyes
• Constant licking
• Difficulty breathing

If a dog is showing any of these symptoms or changes in behavior, you must take them to a veterinary professional straight away. Some dogs can go into life-threatening anaphylactic reactions (A severe reaction throughout the whole body including swelling, rashes and breathing difficulties).

Are symptoms the same for an allergic reaction in puppies?

Puppies will display the same symptoms of an allergic reaction as adult dogs. Every allergic reaction must be taken seriously, but be even more vigilant around baby pups. Because they’re still young, their immune systems have not fully developed, meaning they may not be able to cope with some allergens as well as older dogs.

What causes dog allergic reactions?

An allergic reaction can be caused by several environmental factors. Here are some of the most common types of dog allergic reactions:

Food allergies

Whilst food allergies can be easier to spot in some dogs than others - your pooch may simply vomit up their dinner, a clear way of saying it doesn’t agree with them - sometimes a food-related dog allergic reaction can be harder to notice immediately. 

If you notice a behavior change, they’ve become less energetic, you’ve spotted patches of hair loss, red, inflamed or bumpy skin, or they regularly develop ear infections, or frequent tummy upsets (diarrhea or vomiting), this could all be down to their food. Talk with your vet about which hypoallergenic foods they would recommend.

Skin hives and allergies

Did you know, some dogs are allergic to fleas? Yep, fact! As perfect pet parents, using anti-flea treatment every few months is simply part of your pup’s routine. But be aware if you notice any red patches of skin, itching in one particular spot, or skin hives - tiny red bumps over their skin.  Hives can develop with any cause of allergy, food allergies, contact allergies, or environmental allergies (in the home or outside) even after rolling in grass and playing outside.

Skin hives and allergies can also be triggered by home environment changes, such as changes in detergent or cleaning products. Always consult with your vet and check if any of your home products are known to irritate dog skin.

Seasonal allergies

Dogs can have hay fever just like us - once again, our pooch pals aren’t too different from you and me! Just as with humans, when the seasons change and pollen starts to float freely through the air, you may realize you have a hay fever hound. Aw! Runny eyes, itchy ears and sneezing are a clear tell-tell sign of seasonal allergies in dogs.

Insect and bug allergies

Beware of biting and stinging creepy crawlies, particularly during the summer months. Bug bites from ticks and mosquitos can cause uncomfortable skin reactions in some dogs. Hot-spot skin infections can appear as sore, oozing, regions of hair loss anywhere on the body in response to a bug bite. Ticks and mosquitos can also pass on infections and diseases, so talk to your vet if you're worried about skin reactions that could need treatment. Be extra careful to avoid wasp stings as many pups can have a severe allergic reaction to them which could cause them to go into anaphylactic shock.

Allergic reaction treatment for dogs

The first time a dog has an allergic reaction, your vet will prescribe them one or more allergy relief medicines. These could include oral antihistamines, cortisone creams, medicated shampoo, or Omega-3 fatty acid supplements for food allergies.

Once you can identify what your dog is allergic to, you can make lifestyle changes to actively avoid their allergy trigger. For example, if your pooch your dog is allergic to wasp stings, avoid taking them for walks in the middle of the day when it’s summertime.

Meet our veterinary expert, Lily

This article has been checked by veterinarian Lily Richards BSc (Hons) BVSc MRCVS. Lily qualified from Liverpool University in 2011 and spent 5 years as a veterinarian working in mixed animal practice. As Lily’s passion for exotics and exploring more complicated small animal medical cases developed, she stepped into small animal-only practice. By 2018 Lily was leading a busy branch of a large hospital practice with a fantastic team, enjoying working on both surgical and medical cases. Since falling poorly in 2021 Lily has found a new passion in medical writing. Sharing medical knowledge and writing for the public is a particular passion. 

If you’re ever concerned about your pooch or you’re pet sitting a pup pal, all of our TrustedHousesitters members have free access to our 24/7 Vet Advice line. Similarly, if you are a member and have any extra tips on spotting other allergic reactions in dogs, you can start a discussion on our Community Forum.