Allergies in Dogs - Explaining Allergy Types & Symptoms

Dr. Jason Gagné, DVM, DACVIM
By Dr. Jason Gagné, DVM, DACVIM
Updated: 5/9/20242-4 minutes

If your dog seems to be itching more than usual or has developed other skin or health conditions, they may have allergies.

Just like in humans, allergies in dogs are caused by a reaction of the immune system to a foreign substance.

The three most common are allergies related to fleas, the environment, and at a distant third (and despite popular opinion), food. Fortunately, your veterinarian can help determine the cause of your pet’s allergic reaction.

To help you comfort your canine, here’s what you need to know about the potential causes, symptoms and remedies for dog allergies.

Signs of Dog Allergies 

If your pet has developed an allergy or intolerance, signs might include:

  • Intense itching and scratching that can cause red, irritated-looking skin
  • Chronic ear infections
  • Excessive licking
  • Gastrointestinal (GI) upset
  • Vomiting
  • Diarrhea
  • Excess gas
  • Weight loss
  • Bacterial, fungal or yeast infections

Which Breeds Get Allergies?

Typically, allergies in dogs emerge between one and three years of age, but this is not always the case. While all breeds, including mixed breeds, can experience allergies, certain dogs are predisposed to developing them. These include:

Dog Skin Allergies

Known as allergic dermatitis, skin allergies are common in dogs. They’re often caused by reactions to flea bites or a range of environmental factors.

Flea Allergies

Fleas are a nuisance to dogs, as they’re the leading cause of their skin allergies. When they bite, their saliva irritates the skin. The results can range from mild scratching to severe reactions around the area of the bite.

The most common places to see flea allergy dermatitis are around your dog’s collar area and over the tailhead/hamstring area.

Note dog flea allergies may appear seasonal depending on the environment in which you live. If the winters get very cold, you may not notice symptoms in months when fleas are dormant.

Dogs with flea allergies might scratch, chew or lick their hair or skin. If untreated, this can cause skin trauma or introduce a secondary infection.  

Monthly flea treatments prescribed from your veterinarian can help. Unfortunately, they only kill a flea once they bite, and even a single bite may result in an allergic reaction.  

Indeed, if your dog is allergic to the parasite, one bite alone can make them feel like they’re crawling with fleas (similar to how a person’s entire arm may swell up from a single bee sting).

Keep in mind that, even if your dog is bitten only once, you may not see fleas or flea dirt because of their immune system’s overreaction to the flea’s saliva in that solitary bite.

Dog Environmental Allergies

In addition to fleas, skin allergies in dogs can be triggered by their everyday environment. This is often referred to as atopy. Pollen, mold and dust are primary offenders.

You might see your pet licking their paws and lower legs, scratching their ears and rubbing their muzzle. If you notice a bald patch, this also can be a sign of excessive scratching and itching.

Because dog environmental allergies can be seasonal, they may not affect your dog year-round and you may only notice these signs intermittently.

Dog Food Allergies

Any dog food ingredient could potentially trigger an adverse reaction, but food allergies are usually caused by common protein sources such as beef or chicken (these are the most common in dogs). Grain allergies in food are rare.

Just like people, dogs can develop allergies to foods at any time—even after years of eating them without problems.

It might surprise you to learn that food allergies in dogs aren’t very common. They only make up about 4-10 percent of total allergy cases in dogs and cats.

Diagnosing Dog Allergies

Veterinarians can check for all the obvious signs when determining if your dog has allergies.

Flea bites may be easy to diagnose if flea dirt (dried blood) is still apparent on your pet’s coat. (Remember, though, fleas may not be easily detected as your dog can have a reaction from only one flea’s bite.)

In other instances, it may be challenging to pinpoint the exact cause as there are different types of allergies with the same symptoms.

Veterinarians may propose a blood test or skin test to diagnose environmental allergies. It’s important to note that current research doesn’t support the accuracy of blood tests to detect and predict food allergies.

Dog Allergy Treatment

Treatment for your dog will depend on their specific allergy. Eliminating a trigger substance from their diet can help with reactions to food.

Flea and other skin allergies can be managed through medication as well as medicated shampoo. In addition to treating the source of the problem, they may also alleviate some of the itching and swelling.

Depending on your veterinarian’s recommendations, human antihistamines might be prescribed to control their symptoms. There are also a number of newer medications that help to manage the immune response to the offending allergen.

For severe allergic reactions such as difficulty breathing or vomiting, take your pet to the veterinarian immediately to avoid anaphylactic shock.

Want more health tips for dogs? Learn more from our pet experts or visit our Pet Expertise page.

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