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Signs of Allergies in Dogs: Types and What to Look For

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Like humans, dogs can have allergic reactions, too. The signs of allergies in dogs can vary broadly. At first glance, you might not know if your dog has seasonal allergies, food allergies, or something else.

Not all allergies show up the same way. Understanding the signs of allergies in dogs can help reveal possible solutions, including whether to reach for over-the-counter medications or consult your veterinarian. It’s important to rule out other underlying conditions, such as skin parasites, before treating a dog for allergies.

Canine allergies can range from mild discomfort to life-threatening, so the sooner a dog gets a diagnosis and treatment, the sooner they can feel better.

‌What is an allergy?

‌An allergy starts with an allergen—usually a foreign substance or food. Allergens are substances that stimulate the immune system, causing the body to release a chemical called histamine. That release of histamine results in inflammation, which triggers the clinical signs usually associated with allergic reactions (like redness, swelling, and itching).

Why dogs get allergies

Allergies are multifactorial, meaning they are caused by a combination of genetic and environmental factors. Each type of risk factor contributes to the allergic response in different ways. Environmental risk factors (allergens) are required for allergies to occur, while genetic risk factors are responsible for ramping up a dog’s immune system.

Such genetic risk factors can play a role for an individual dog or entire breeds. Allergies can run in families, and some breeds are more likely to develop certain types of allergies than others. Knowing your dog’s genetic history is a tool that can help you be prepared.

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Which allergies are most common in dogs?

‌There are several types of allergies that can affect dogs: flea, environmental (sometimes called atopy), food, and contact allergies.

  • Flea allergies can cause flea allergy dermatitis, one of the most common skin conditions in dogs, but prevention goes a long way. Flea allergies can happen anywhere there are flea populations. They can also occur any time of year. 
  • Environmental allergies can be seasonal and peak at specific times of year, especially spring and summer. Exposure to these allergens occurs via skin contact or inhalation. Environmental allergies can also be caused by indoor and non-seasonal substances, such as dust mites, molds, and many others. 
  • Food allergies result when the body has an abnormal immune response to an ingredient in food.
  • Contact allergies are relatively uncommon in dogs. These allergies can be caused by ingredients in medication, hygiene products, fabrics, or something else. With contact allergies, a dog would likely show redness or irritation of the skin.

According to Embark data:

  • 10.7% of dogs have an environmental or seasonal allergy
  • 5.3% of dogs have a food allergy
  • Of the dogs who have food allergies, 60.6% are allergic to an animal protein and 22.4% are allergic to a grain

Types of canine allergies

Flea allergies

‌For some dogs, flea bites can lead to canine flea allergy dermatitis (FAD). FAD in dogs is due to hypersensitivity to substances in flea saliva, and it can cause severe skin reactions long after the flea is gone.

Spotting fleas or flea dirt helps with the diagnosis, but sometimes, a dog can develop signs of flea allergy dermatitis from one brief flea bite. A recent history of dog parks, boarding, grooming, or interaction with other animals could make flea exposure more likely.

With flea allergies, preventing flea bites in the first place is the most effective way to safeguard your dog’s health. Read more about why regular flea and tick prevention is a crucial part of your dog’s care and how to protect your dog from flea bites.

Environmental allergies

Environmental allergies can be difficult to determine, but sometimes it helps to pay attention to whether they are seasonal or year-round. Like people, dogs have mast cells in their skin that store histamines for a quick immune response to an allergen. Although some dogs react to seasonal allergens with a runny nose or sneezing, they are much more likely to get itchy skin. 

Environmental allergies in dogs can happen from a variety of indoor and outdoor allergens. Some of them include:

  • Insect bites
  • Tree pollen
  • Grass pollen
  • Flower and weed pollen
  • Dust and dust mites
  • Mold spores
  • Mildew

Atopic dermatitis is an inflammatory, chronic skin condition associated with environmental allergies. It is influenced by both genetic and environmental factors. By one estimate, atopic dermatitis affects 10 to 15% of dogs.

Some breeds appear to be affected by atopic dermatitis more frequently. These breeds include Golden Retrievers, Labrador Retrievers, Dalmatians, Scottish Terriers, French Bulldogs, West Highland White Terriers, Boxers, Chinese Shar-Peis, Lhasa Apsos, and German Shepherds.

Allergy testing can be used to determine the underlying environmental trigger that a dog is reacting to. The two main types of allergy testing are 1) intradermal (skin) and 2) serum (blood).

Food allergies

Dogs can also have allergies to components in food (sometimes called adverse food reactions). If a dog is allergic to a type of food, they can show skin reactions, gastrointestinal reactions, or both.

Like canine atopic dermatitis, food allergies in dogs are caused by an abnormal reaction of the immune system to a substance. While the cause of food allergies is not completely understood, it does require a dog to be exposed to the allergen. 

A review of several studies determined that the most common ingredients responsible for food allergies in the studied dogs were beef, dairy, chicken, and lamb. Wheat, soy, and corn were the most common plant-based ingredients implicated in food allergies; however, allergies to these three ingredients were less prevalent than the four common meat-based allergies. If a food allergy is suspected, your veterinarian may discuss performing a strict food trial, which is currently the only reliable way to diagnose a food allergy. 

Some dog breeds are more likely to develop food allergies, including Labrador Retrievers, Cocker Spaniels, and West Highland White Terriers

Read more about food allergies in dogs, common trigger foods (such as proteins or grains), and how to tell the difference between food allergies and food intolerances.

‌‌‌Signs that a dog is having an allergic response

The following five signs may indicate that your dog is having an allergic reaction.

1. Skin issues: itching, excessive licking, red and inflamed skin, and hot spots

‌A dog who is itching on their face, belly, groin, rear, base of their tail, or side could be showing signs of an allergic response. Because itching can be a sign of atopic dermatitis, food allergies, and flea allergies, this alone does not help us identify the allergen. The location of itchiness can give clues—for example, itching primarily on the back and base of the tail could hint at a flea allergy.

‌Excessive licking due to itchiness is one of the most consistent symptoms of dog allergies. It can happen with all allergy types, and it can become so intense that it causes hair loss, bald spots, and areas of raw skin. Excessive licking of the feet, rear end, and inner thighs is particularly common. 

‌Irritated skin quickly turns red and inflamed, and it can feel warm to the touch. Dogs can get red, inflamed skin from any allergy. However, if itchiness is causing them to lick, bite, or scratch at themselves excessively, the skin may also become traumatized, leading to more significant medical issues. 

‌Hot spots (also known as pyotraumatic dermatitis) are moist, itchy, and painful lesions seen in some allergic dogs. Although allergy-related itchiness is likely an inciting factor, self-trauma to relieve the itch plays an important role in hot spot formation. Hair loss is often evident at the site of the lesion and surrounding hair is commonly matted with dried pus. If left alone, hot spots may dry up, scab and heal. However, hot spots commonly result in a recurring cycle of itch and self-trauma, making resolution challenging in some cases. Secondary infections of hot spots are also common and may require antibiotic therapy. 

To treat or prevent these lesions, it’s important to stop your dog from traumatizing the hot spot any further. Next, consult your veterinarian to determine the underlying cause.

2. Repeated ear infections

Ear canals are essentially modified skin. Repeated ear infections are a common indication of an underlying sensitivity to food or something in the environment.

3. Red, runny eyes

‌Red and runny eyes can happen due to certain environmental allergies when allergens are airborne. If your dog develops yellow or green discharge from their eyes, has crusty and swollen eyes, or is squinting or pawing at their eyes, contact your veterinarian.

4. Vomiting and diarrhea

Vomiting and diarrhea are common signs of food allergies in dogs. Some dogs may also exhibit gastrointestinal noises, flatulence, and soft stools. Dogs can also develop vomiting and diarrhea from dietary indiscretion when they eat something they shouldn’t, but this is not considered an allergic response. 

‌5. Swelling and hives

Dogs with more severe, acute allergic reactions can get swelling and inflammation on the face, ears, paws, eyelids, muzzle, or lips. This swelling is a direct result of the histamines released and can happen from many types of allergies. If you see swelling on your dog’s face, contact your veterinarian as soon as possible.

Hives look more like a rash with raised bumps, and they can appear in response to lots of triggers, including insect bites, medications, foods, and more. In dogs, hives might be the only sign or they can be associated with a more severe systemic allergic reaction, called anaphylaxis. If you notice hives, contact your veterinarian.

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Emily Clayton Contributor

Emily Clayton is a seasoned writer who has been producing high-quality content since 2013. Her primary expertise and writing interests are in the lifestyle, health, and wellness industries; food culture; and art/design fields, yet she is skilled at content creation for a range of subjects and loves diving into research to produce original, compelling work.

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