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Hives in Pets: What They Mean and What Causes Them | VetDERM Clinic

Hives in Pets: What They Mean and What Causes Them


Hives (also called urticaria) are the development of swollen, pale red bumps or welts on the skin. These little lesions will usually appear suddenly and are often related to an allergic reaction against something. The presence of hives can be seen as a single bump, or as a collection of more than a few bumps. The phrase ‘wheal-and-flare reaction’ related to inflammation is the cause of hives.

Hives are commonly seen in humans. Surely, almost everyone has had an episode of hives at one point or another (as single lesion or as collection of a few lesions).

  • I have had them on my hand from retrieving a soccer ball from a shrub that had pointy thorns I chose to ignore!
  • Mosquito bites can cause hives.
  • Kids can have hives from allergies to food, especially at a young age.
  • Some people may get rashes from being outdoors during activities such as camping or hiking!


Pets too can be affected by hives due to food, flea, or environmental allergies, occasionally with a contact allergy reaction or a possible vaccine reaction leading to the raised bumps!


These lesions are not as easy to note on a pet as it is on human skin due to the dense hair coat that dogs and cats possess in comparison. Thus, instead of red, raised welts, all you may notice on a pet with hives is multiple, small raised tufts of hair. These raised bumps may cause itchiness, or not bother the pet at all. If hives are present on areas with less hair they might be easy to see—for example, on a dog’s belly.

When hives are present, usually the pet doesn’t even notice the difference when you touch affected and unaffected skin with your finger. They may sometimes be sensitive to touch, and can also be itchy.


Itchiness may be related to the underlying main reason why hives developed in the first place. Certain causes for the hives may induce itch on their own (flea bite allergy for example)!


If these lesions resolve themselves within a few hours, it was surely hives. If they don’t self-resolve, or worse, new lesions come up, or the size of lesions increases, it should be time to look for medical treatment for your pet. The underlying cause for these lesions needs to be found to make the pet better.

Hives can be acute or chronic in nature. In humans, if hives have been a problem for less than 6 weeks, they are considered acute (short-term problem). If the signs go on longer than 6 weeks, it is chronic hives (long lasting). For pets, it is difficult to separate the presence of hives in to these categories but a similar scale can be used.

What are Hives?

Hives, or urticaria, is the outcome of localized histamine release in the skin causing blood vessels to dilate. The inflammation locally leads to small red, raised welts and bumps (the hives). The small bumps can merge together and form large swollen spots. The larger swollen areas are called angioedema, which is a form of the simpler term edema (collection of fluid under skin). Hives in pets can last from a few minutes to days, even months!

Hives and Allergies

Hives are most commonly caused by an allergic reaction. Allergic reactions can happen from many things, including a pollen allergy, a food allergy, a mosquito bite, a bee sting, etc. Some pets can be sensitive to the point where they develop multiple skin allergies to a mix of allergens. Environmental allergies are due to many reasons including grass pollen, tree pollen, house dust mites, etc.

Also, various food allergies exist in dogs and cats. Some dogs and cats may be affected by multiple food and environmental allergens. Other causes for hives may include medications, supplements, and vaccinations.

What Can You Do to Find the Cause?

It can sometimes be quite easy to find the cause:

  • If your pet was at the park and chasing a bee, the presence of hives could be due to the bee not enjoying your pooch’s playful behaviour as much!
  • If hives seem to come up every time you go out for a dog walk, it could be something in that environment that your pet is sensitive to.
  • If your pet got a new treat and immediately developed bumps on skin or a swelling of the face, perhaps the new treat could be the problem?


Sometimes the cause may not be that obvious, especially if nothing has changed in your pets’ routine. Hives can come up due to a delayed reaction to something that changed a few days back, including the location or season.


For Anything Unusual, See the Vet

A food allergy or environmental allergies that cause persistent hives are tougher to diagnose. A veterinary exam is always a good idea. If the signs of hives persist, it will be a good idea to know if it is actually hives or a similar condition that needs to be treated differently. A veterinary dermatologist will usually obtain detailed information about your pet so that a cause can be found quickly.

When anything is abnormal about your pet’s skin, it is best to bring your pet to your veterinarian or vet dermatologist. Hives can become infected by bacteria due to excessive scratching. A skin infection itself can look very much like hives. Treatment for a skin infection in dogs or cats and for hives is very different from each other. In the case of allergies, hives could be the beginning of a more severe allergic reaction. If you notice your pet’s face is swelling up or they’re having breathing difficulties, your pet definitely needs immediate veterinary attention.

At-Home Relief

Bathing your pet in cool water can soothe their skin and also relieve itchiness and inflammation. Bathing also helps wash off any possible irritants that may be causing the reaction. This helps provide relief, but it may not help for all causes of hives.

When it comes to home remedies, always be sure to ask your veterinarian before attempting any home remedies for your pet. They may prescribe topical products or prescription relief for your pet’s hives depending on what the allergic reaction is due to. Finding out what caused the hives in the first place should help you prepare for future possible episodes if they do occur again.




Dr. Jangi Bajwa is a Board certified veterinary dermatologist at VetDERM Clinic in Surrey BC. He is also the dermatology feature editor for Canadian Veterinary Journal. Dr. Bajwa’s special interests include otitis and allergic disease in pets; as well as helping improve quality of life of pets and their families.


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