Rashes and Hives (Urticaria) in Dogs

Urticaria is a skin condition, more commonly known as hives or rashes. Though urticaria is considered to be relatively rare in dogs, any breed can be affected.

Urticaria is the dog’s immune system response to coming into contact with a chemical or allergen that results in red, itchy patches — or sometimes even bumps on the skin. Dog hives can appear suddenly, and disappear again quickly — but for the time your pet is affected by rashes, they can cause itching and irritation, making a dog uncomfortable.

And, while urticaria in dogs is often harmless and resolves itself, some cases may require treatment and pose a risk of more serious issues, depending on a dog’s ongoing reaction to the allergen that has triggered the hives.

There’s a chance, albeit rare, that a dog can experience swelling in the mouth and the throat, which can then block airways — leading to inevitable breathing issues and a serious condition called anaphylaxis. An anaphylactic shock is a life threatening, emergency situation and needs urgent veterinary intervention.

That’s a worse case scenario, but as a pet parent it’s important to be aware of the impact urticaria in dogs can have. Discover more about what causes hives in dogs and what to do if you’re asking, ‘why is my dog breaking out in hives?’

If your dog is suffering from urticaria, you’ll soon know about it. Symptoms generally appear a few hours after your dog comes in contact with the allergen or chemical causing the allergic reaction. While some pet parents might report that ‘my dog has bumps all over his body itching’, others could notice a change in their pet’s breathing, which is an indication of an allergic reaction.

Symptoms can vary, though. The most obvious symptoms are red patches of skin or wheals that define the condition. These can be seen anywhere on the body but are mostly noticed on the back, legs, flank and neck.

Other clinical symptoms for dogs suffering from urticaria can include:

• Bumps on skin, face ears or tongue
• Difficulty breathing
• Swollen eyes or face
• Excessive scratching
• Drooling
• Fever
• Lethargy
• Anorexia

Types of Urticaria

While urticaria isn’t generally subdivided, there are a couple of specific types of the condition that pet parents should be aware of.

Anaphylactic — This type of urticaria causes swelling in the nose, mouth, and throat of the dog. This is potentially life threatening to the dog as the swelling could become so severe that the dog’s airway is blocked, causing suffocation.

Chronic — This happens when the allergen cannot be identified or removed from the living space of the dog.

Heat Reflex — This is an uncommon affliction where the dog suffers from heat rash.

Why is my dog breaking out in hives? It’s an obvious question and one that every concerned pet parent will no doubt ask if their pet is suffering with urticaria. The answer is that what causes hives in dogs can be any number of reasons, including:

• Vaccinations (particularly rabies and bordetella)
• Chemical reaction (particularly to lawns treated with pesticides)
• Food allergies
• Toxic plants
• Inhaled allergens
• Stress
• Exercise
• Intestinal parasites
• Prolonged exposure to heat (including heatstroke) or sunlight
• Illness
• Milk retention (during female heat cycle)

Diagnosis of urticaria will require an accurate health history of your pet, to see whether your dog has had hives before.

The veterinarian may have an indication of what is causing the condition based on the symptoms you describe as accompanying the skin outbreak as well as the type of rash that’s present upon examination.

If the first consultation is via email, an image of your pet’s skin at its worst will be a helpful diagnostic tool for the veterinary team to make an initial assessment. When attending in person, skin scrapings may be taken and analyzed under the microscope to further reach a definitive diagnosis.

Blood tests may be indicative of markers related to urticaria; a description of your dog’s diet, grooming aids, recently administered supplements, and possible exposure to plants that could be skin irritants will be helpful to the veterinarian. If allergies are suspected, testing may be done or an elimination diet may be suggested.

Dog hives can often disappear as quickly as they come on, but other rashes may linger and possibly cause distress for your pet. These will need to be treated — sometimes Benadryl can be administered to relieve symptoms.

Benadryl, as prescribed by your veterinary caregiver, can also be used to prevent anaphylactic swelling. It’s important to seek professional treatment in the case of anaphylactic swelling as the dog's life may be in danger.

In more severe cases of urticaria in dogs, a steroid may be administered, particularly if your pet is finding the condition to be itchy. Secondary conditions are possible if the skin becomes excessively red or raw.

Because dog hives are typically self-limiting, recovery and the prognosis is usually great. In severe cases, if there’s swelling in the mouth or airways, the dog will need medical intervention to be able to breathe. But, providing the correct treatment is followed and administered, recovery should be complete in a short period of time — a few days.

There are steps a pet parent can take to try to prevent urticaria in dogs from occurring in the first place. If the hives and rash appeared because of a food allergy, look into exactly what caused the reaction.

The most common food allergens for dogs are chicken, wheat, and beef. There are tests available from your veterinarian that can list your dog’s food allergens, in order of severity.

Otherwise, you may choose an elimination diet to determine the allergen. Most dogs see dramatic improvement after eliminating chicken from their diet due to some processing methods of chicken in dog food. A diet focused on fish proteins may help soothe and restore the dog’s skin no matter what the allergen. Adding fish oil to your dog’s diet can also help.

If your dog suffers from another outbreak of hives or a rash, keeping Benadryl in the household can help provide a swift form of treatment — especially if the allergen remains unidentified. Removing common allergens or pesticides from the home is also advised.