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Dog Allergies: Signs, Symptoms, Diagnosis & Treatment

Wondering if your dog has allergies? Learn about the most common types of allergies in dogs, what causes them, and how to best treat them.

Aly Walansky

Updated May 17, 2023 • Published January 15, 2021

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Dog Allergies: Signs, Symptoms, Diagnosis & Treatment

Suffering from allergies isn't fun for anyone—dogs included. The types of allergies that dogs get and their reactions may be somewhat different than humans, but they can be just as stressful and confusing.

If your pup is experiencing allergies, it's important to get to the bottom of what's causing them. Let's dig a little deeper into the types of allergies dogs can get and how to diagnose and treat them.

The different types of dog allergies

There are three different types of allergies in dogs:

  • Flea and insect allergies

  • Environmental allergies

  • Food allergies

Flea & insect allergies

A flea or insect allergy is the most common allergy in dogs—your pet reacts to the flea's saliva.

Flea allergies in particular are by far the most common type of allergy that we see. Fleas or other parasites could be on the skin of the dog, leading to itching, scratching, and biting. A monthly prescription oral medication is recommended to kill fleas, prevent secondary skin infections and diseases transmitted by fleas, and keep your dog healthy.

Just one flea bite can cause your dog to itch, scratch, and chew for days. In fact, in a lot of flea allergy cases, only one or a few fleas trigger an allergic response, so it's common to not see a flea on your dog even if this is the cause. Fleas can be very hard to find even for a veterinary professional.

Environmental allergies

Seasonal allergies are the second most common type of allergens that cause an allergic response in dogs. Environmental allergens such as pollens, molds, trees, weeds, and grasses can create an atopic allergy response in dogs with a sensitivity to any of those allergens. Dust particles and dust mites can also wreak havoc on our dog’s immune system.

Food allergies

Food allergies may be the itchiest of the allergens, but also the rarest in dogs. Only about 5% of all dogs with allergic dermatitis have a food allergy. The most common ingredients are beef, dairy, wheat, and chicken, with beef being the highest percentage. If you suspect your dog has a food allergy, it's best to consult with your veterinarian to determine what food would be the best option to feed them.  

Signs your dog has allergies

If your dog has allergies, they can show symptoms similar to humans. These include:

  • Rashes

  • Itching & scratching

  • Gastrointestinal upset

  • Hair loss

  • Watery eyes

  • Nasal discharge

  • Sneezing

  • Respiratory congestion

  • Chronic ear infections

  • Inflamed and irritated paws

Let's break down some of the more common signs we see with allergies, including rashes, itching and scratching, and gastrointestinal upset.


A typical sign your dog is allergic to something is when their skin has a reaction, becomes red and irritated, and sometimes forms a mild rash. Skin rashes can appear from contact with an allergen or from something they ate or inhaled. It can be difficult to determine the source of the allergen since there are multiple ways for you dog to be exposed.

A more severe skin reaction is hair loss, often in patches with scabs and pustules. Fleas, intestinal parasites, and a diet that is primarily composed of low quality ingredients can all cause hair loss. Keep in mind that endocrine diseases can also present in a similar way to an allergen, so it's best to consult with your veterinarian or a Pawp Professional before assuming the hair loss is due to an allergy.

Itching & scratching

The most common sign of allergies in dogs is itching of the skin. Dogs with skin allergies will constantly scratch, chew, and bite their skin. Areas that the dog focuses on can determine what type of allergy may be responsible for the reaction. A flea allergy will cause the dog to concentrate on the area above the tail base, down the legs, and on the abdomen. Flea bite allergies can also cause the dog to react suddenly and even cause hyperactivity. 

Atopic dermatitis is the most common skin allergy and causes the dog to bite, scratch, and chew the whole body—often focusing on the feet and legs. 

Gastrointestinal issues

If your dog has a food allergy, gastrointestinal (GI) issues are usually the first signs you may notice. Vomiting, diarrhea, excessive gas, and nausea can be caused from an allergy.

How to treat allergies in dogs

Diagnosis and treatment of allergies in dogs can be time-consuming, expensive, and frustrating, but patience is vital. If you think your dog has an allergy, reach out to your veterinarian or a Pro at Pawp to discuss the next steps.

How to treat flea allergies

Preventing a flea from biting your dog is the first step in controlling a flea allergy. Oral flea products are absorbed into your dog’s body and dispersed throughout giving optimal coverage. Topical products can be unreliable since the product has to be delivered through the sebaceous glands in the skin. If your dog has dry skin, the product is rubbed off, or is stripped off with shampoos, it's less effective.

Once it's determined that your dog does have a flea allergy through an examination and testing by your veterinarian, monthly flea control (for your dog and the environment) along with medications to treat any secondary infections will most likely be the best route for treatment.

How to treat environmental allergies

If a flea or food allergy has been ruled out or confirmed but is not responding to treatment, the next step is to test for environmental allergies. An intra-dermal skin test or a serum allergy test can be performed to identify the severity of the allergen.

Once the allergens have been identified, an immunotherapy treatment plan will begin by injecting your dog with a specially formulated serum on a weekly schedule. This will create a hyposensitization of your dog’s immune system to the allergen.

How to diagnose and treat food allergies

Diagnosing a food allergy can be accomplished with a food trial or an allergy serum test. A food trial consists of feeding your dog a prescription hydrolyzed protein diet that will prevent immune responses. All treats, additives, supplements, and even oral prescription preventatives should be eliminated completely from your dog’s diet. Only water and the prescription diet should be fed. These diets are fed for eight to 12 weeks to determine a response of improvement or not. GI issues usually start to improve in 2-3 weeks and skin issues can improve in 4-12 weeks

If improvements are seen, your dog can continue on the prescription diet lifelong, or you can slowly add back ingredients to see if your pet has an allergic reaction. A novel protein diet is often prescribed to feed since it provides protein sources that are less likely to create an allergic reaction. 

When to talk to a vet about dog allergies

Along with diagnosing the underlying cause and treatment, your dog will need supportive care to stop the itch, prevent the irritation, and treat any secondary bacterial infection. Your veterinarian will be able to prescribe the best medications needed for your dog, including medicated shampoos and wipes.

As with humans, once the allergen has been identified, it can be managed and treated through the guidance of your veterinarian. It's prudent to monitor your dog’s responses to any new allergen sources or reintroduction of any previous allergen sources and report any changes to your veterinarian. Managing allergies in dogs can be a lifelong process, but with the proper veterinary guidance, your dog can live a happier and more comfortable life.


Reviewed and fact-checked by

Mika, RVT at Pawp

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