Why does my dog suddenly have hives

By Isabella Storyclaire

last updated September 16, 2024

Contributions sourced from

Dog Hives (Urticaria | welts): Causes, Diagnosis & Treatment

What Are Dog Hives (Urticaria)?

Hives, otherwise known as urticaria by medical professionals, are one abnormality you may see. They occur when your dog is allergic to something, such as an insect, medication, or food. Recognizing hives in dogs and understanding the cause is essential to relieving your dogs discomfort and preventing dog hives in the future.

What do dog hives look like?

Dog hives look like raised bumps on the skin, usually about the size of a nickel.
Hives are usually red in color; however, you may not notice redness if they are on a very furry part of your dog. In this case, your pets hives may only look like fur-covered bumps. Sometimes, its difficult to see the raised bumps, and you may only feel them when petting your dog.
Dog hives can appear anywhere on the body, including the face, tongue, neck, legs, chest, abdomen, or back. They can affect just one area of the body or the entire body.
Dog hives are very itchy. This may be the first thing you notice before seeing or feeling hives on your dogs skin. Your dog will likely be trying to scratch, lick, or bite the areas affected as it will be itchy.
Hives usually happen very fast within minutes after exposure to whatever caused them.
You may notice excessive drooling and a swollen/puffy face if the hives affect your dogs throat or mouth.

What causes hives on a dog?

Dog hives are almost always related to exposure to an allergen. Once exposed to an allergen, mast cells in your dogs body release a substance called histamine. Histamine causes blood vessels to dilate, which leads to raised welts on your dogs skin.

The most common allergens causing dog hives include:

Insect bite or sting, or ingesting an insect (photo recommendation: dog playing with bee)
Vaccinations
Acute allergic reactions to medications (chemotherapy, vitamin K, antibiotics)
Food allergies
Environmental allergies (grasses, trees, mold, dust mites, etc.)
Contact allergens such as shampoos, insecticides, cleaning products
Ingesting or skin exposure to toxic plants

Much less common causes of hives in dogs include prolonged exposure to extreme temperatures (hot or cold), strenuous exercise, parasites, or significant psychological stress.

Insect bites/stings, food, and medications are the most common causes of hives in dogs.

How are dog hives diagnosed?

As a pet parent, it can be worrisome to see these skin rashes, but luckily, for your vet to diagnose your dogs hives. Your vet will use a combination of your history and their physical examination findings.

Its essential to think about anything new your dog may have been exposed to. Did you see them playing with a bee? Were they recently vaccinated? Did they start a new medication or a new food? During the physical exam, your veterinarian will look at your dogs skin to evaluate hives and where the hives are located.

If your veterinarian is having trouble diagnosing your dogs hives or the reason for their hives, they may perform additional diagnostics, such as blood work, skin cytology, skin scrapings, or fecal analysis.

How to treat & get rid of dog hives?

Treatment for hives in dogs can be simple or more extensive, depending on the cause, severity, and duration of the allergic reaction.

To get your dog quick relief from the swelling and itchiness related to hives, your veterinarian will usually administer an injection of diphenhydramine (an antihistamine) and a corticosteroid. Once your dog is feeling better and discharged from the hospital, your veterinarian may also recommend that you continue giving your dog Benadryl two to three times a day at home for a couple of days.

To prevent hives from reoccurring, you need to understand what caused them in the first place so that you can avoid the allergen in the future. If there is no apparent cause for your dogs hives (such as insect bite, medication, or vaccinations), it may be more challenging to understand how to prevent hives in the future. Environmental and dietary allergies are two possible causes of hives that may require further diagnostics and treatment.

Environmental allergies

If your dog has recurrent hives or has other signs of allergies, your veterinarian may recommend testing for environmental allergies with serum allergy testing or intradermal allergy testing. With these results, your veterinarian can create a plan to desensitize your dog to these allergies with allergen-specific immunotherapy.

If you determine that you cannot eliminate the allergens in your dogs environment or pursue allergen-specific immunotherapy treatment, your veterinarian may recommend:

Giving your dog daily antihistamines (such as Benadryl, zyrtec, or hydroxyzine)
Giving your dog other prescription-strength allergy medications such as apoquel or cytopoint
Starting daily skin health supplements, such as omega-three fatty acids.
Frequently bathing your dog with medicated high-quality shampoo

Food allergies

Allergies that stem from food can also cause recurrent episodes of hives in dogs. The most common cause of allergies in dogs include chicken, beef, dairy, and egg 2. Recurrent episodes of hives can also be related to dietary allergies. To diagnose a food allergy, your veterinarian may recommend a diet trial for 6-8 weeks with a prescription food or an over-the-counter diet with a different protein source, like fish or venison. If your dog responds positively to a food trial, you can continue the special diet long term.

Are dog hives dangerous?

Dog hives are rarely life-threatening. However, there are a few less common situations where hives can affect your dogs breathing and become dangerous.

Hives in the face, neck, or throat can cause severe swelling that impacts breathing, which can become life-threatening.
The presence of hives anywhere may indicate your dog is having or about to have an anaphylactic reaction, which causes constriction of airways and difficulty breathing. 3 Besides hives, other signs of anaphylaxis include vomiting, diarrhea, facial swelling, drooling, blue gum color, and collapse.

If you notice that your dog has hives, pay particular attention to how they are breathing and for any other concerning changes in their behavior. If you are concerned your dog may be having severe allergic reactions, take them to the emergency room immediately to rule out a medical emergency.

At-home remedies for dog hives

If possible, take your dog to the veterinarian if you notice they have hives, especially if this is a first-time problem. If your dog chronically or intermittently has hives and the issue has previously been discussed with a veterinarian, some at-home remedies may help relieve the allergic reaction.

If the hives are not affecting your dogs face, neck, throat, or ability to swallow, you can administer Benadryl by mouth. Always discuss if this is appropriate for your dog with your veterinarian first and receive instructions about dosage and frequency.
If the hives were caused by a contact allergen (such as grasses/trees or chemicals) or insect bites you can help relieve itchiness by bathing with a gentle oatmeal-based dog shampoo can help your dog feel more comfortable.
Apply a cold compress to the hives or the most severely affected areas of your dogs skin. Be careful never to apply a cold compress for more than 10 minutes at one time, and always wrap the ice or cold object in a towel before applying it to your dogs skin.

Hives and Rashes (Urticaria) in Dogs

Hives or skin rashes (urticaria) are localized patches of red, swollen, usually itchy, skin. They often develop and disappear suddenly. Hives are relatively uncommon in dogs. The most frequent causes are insect bites or stings, shampoos, and medications. Other causes include contact with toxic plants or chemicals. Friction, sunlight, heat, exercise, stress, and genetic abnormalities may cause or intensify the rash. Hives may develop after inhaling or consuming allergens. Hives can be seen while a dog is in estrus ("in heat") or seen in puppies with intestinal parasites ("worms").

The wheals (eruptions) appear within a few minutes or hours of exposure to the causative agent. In severe cases, the skin eruptions are preceded by fever, poor appetite, or dullness. They can develop on any part of the body but occur mainly on the back, flanks, neck, eyelids, and legs. In advanced cases, they may be found on the mucous membranes of the mouth, nose, lining of the eyes, rectum, and vagina.

Often, hives disappear as rapidly as they arise, usually within a few hours. Treatment may not be required. They may return rapidly if exposure to the cause is not eliminated, however. Also, if your dog develops hives after receiving a vaccination or medication, contact your veterinarian immediately to see if treatment is needed. Treatment may include rapid-acting corticosteroids. If hives are chronic, environmental or food allergens should be considered as potential causes. Death does not commonly occur, unless anaphylaxis (a severe allergic event) or swelling of the respiratory tract is present.

Also see professional content regarding urticaria.

Why Does My Dog Have Hives?

What are hives?

Hives are skin rashes or welts that are red, swollen, and usually itchy. The red skin welts can develop on any part of the body, including the dogs face, throat, lips, and ears. Most of these reactions are localized and often resolve on their own.

Hives in dogs are not as easy to detect as they are on the skin of people because of the dogs dense hair coat. You may see the rashes on areas of the dogs body with less hair but other than that, all you may notice are several small raised tufts of hair that indicate the presence of the raised welts. The skin welts may be itchy or may not bother your pet at all.

Causes of Hives in Dogs

Hives develop when there is a localized release of histamine in the skin. This can cause the dilation of blood vessels in the area. The local inflammation eventually gives rise to small reddish welts and bumps that are collectively called hives. Small hives can merge and form larger skin welts and bumps.

There are many known triggers of hives in dogs. Any allergen that your pet is hypersensitive to can cause hives. Some of the most common include:

Some factors that can intensify the rash include exposure to sunlight, friction, stress, heat, and exercise.

In a study about urticaria in dogs, insects, food, and drugs were the most frequently detected triggers. Identifying the trigger factor of your pets hives can help you prepare for possible episodes in the future. Hives may return rapidly if your dog continues to be exposed to the trigger(s).

Symptoms of Hives in Dogs

Areas of redness and swelling develop on the dogs face, legs, and abdomen.
Swelling around the dogs muzzle can lead to drooling
Excessive scratching
The dogs eyes appear to be closed as a result of the swelling around them.
The hives often appear as raised circular bumps on the skin surface.

There are instances when the reaction can worsen if appropriate treatment is not given. This could be life-threatening as the swelling could cause the dogs throat to close. Affected dogs can also suffer from intense itching, causing them to scratch excessively, which can also make the reaction more severe.

Are hives harmful to my dog?

If skin swelling is caused by bee or wasp stings, there may be a dramatic swelling around the dogs face and lips. There is a possibility that the swelling could progress to the dogs throat. This serious reaction is called anaphylaxis, and when this happens it could compromise the dogs respiratory passages, making it difficult for the dog to breathe. This is one of the reasons why an anaphylactic reaction should be treated as a medical emergency. Prompt veterinary attention should be sought.

Fortunately, this life-threatening reaction is very rare. Most cases of hives in dogs are self-limiting and dont pose a significant health threat to your pet.

How to Treat Your Dogs Hives

Depending on the severity of the allergic reaction, your vet may prescribe antihistamines or rapid-acting corticosteroids. When administered by injection, these medications could produce dramatic improvements within a few minutes.

Can my dogs hives be treated at home?

Once the dogs exposure to the allergen has been removed or minimized, hives tend to resolve on their own. But it can usually take between 24-72 hours to clear up. To prevent excessive scratching which can make the skin raw, apply ice or a cold towel on your pets skin. The cold can help soothe and alleviate the itching.

Bathing your pet in cool water is also another way to soothe his skin and relieve the itching and inflammation. Irritants and allergens on your pets skin can also be washed off during bathing.

There are also natural remedies for skin itching that you can try at home. These include chamomile and herbal tea soaks, apple cider vinegar water spray, an oatmeal bath or paste, coconut oil, and plain yogurt.

You can also ask your vet about home remedies for your pet. These may include topical products or prescription medications depending on the cause and nature of your pets allergic reaction.

While most cases of hives can be treated at home, contacting your vet is recommended because of the possibility that it can lead to more serious reactions as the allergy spreads to other parts of the body.

If your pet has recently received a vaccine or medication and has developed hives, contact your vet immediately so you can be instructed on what to do.

Ways to Prevent Hives in Dogs

Avoid exposing your dog to the allergen culprit. This is the best way to prevent hives in dogs. But this is easier said than done. Allergens abound in your dogs immediate environment or they could be in your pets food. There is a need to undertake measures to identify the allergen culprit so you can minimize or altogether prevent your pet from exposure.

If your dog reacted to a particular vaccine in the past, your vet may give your pet a shot 10-14 minutes before the administration of the vaccine. Your vet may also deem it necessary to modify future vaccination protocols for your pet to minimize adverse reactions.

Why is my dog itchy?

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