Dogs and Allergies

Why is my dog so itchy???

Many things cause itchy skin in dogs, but the MOST COMMON REASON BY FAR is ALLERGIES!

Canine allergies are incredibly common. In September and October (peak allergy season), about half of the patients we see are itchy dogs. Allergies in dogs cause skin irritation and itch (licking, scratching, chewing). Once the skin is inflamed, they go on to develop secondary infections (skin rashes, ear infections, hair loss). This can cause significant pain and irritation to dogs and to their sleepless owners!

Three major types of allergies in dogs:

1. Environmental allergies (Atopy, Atopic Dermatitis)

Tree, grass, and plant pollen, animal dander, mites, dust, molds... these small particles waft through the air and settle onto the grass and ground. Dogs come into contact with these allergens and develop an irritating allergic reaction on their feet, bellies and then across their whole bodies (and especially their ears).

2. Food allergies

Food allergies look almost identical to environmental allergies (itchy skin, ear infections, belly rashes, etc). However, there is a very different cause. Food allergy is caused by an adverse reaction to something in a dog’s diet, typically a protein. Beef and dairy are the most common food allergies, but a dog can be allergic to ANY food ingredient. Food allergies are much less common than environmental allergies.

3. Flea allergies

When a dog gets fleas, it is always irritating to both the dog and the owner. However, when a dog as an ALLERGY to its fleas, a single flea bite can cause a huge amount of itching and irritation across the whole body.

How can we tell the difference?

It is often very difficult to be sure which kind of allergy your pet has. This is because the signs of these different allergies overlap considerably. Here are some of the clues we look for.


Environmental allergies often have a seasonal component. They can peak any time in the spring-fall, but August-October is the prime season. However, some dogs experience environmental allergies year-round.

-Diet trials:

To determine if a pet has a food allergy, they should be given a full diet trial. This means feeding a highly specialized home-cooked diet or a prescription hypoallergenic diet for 2-4 months and doing a food challenge at the completion of the trial.

-Flea clues:

Flea allergies often presents with the most intense itching on the rump. Additionally, evidence of flea infestation is usually (but not always) present at the same time.

What can we do to help these dogs?

-Treat the infections:

When dogs develop skin infections or ear infections (overgrowth of their own yeast and bacteria), they need treatment. Ear cytologies and skin cytologies are needed to tell what is growing on the skin and in the ears and to monitor progress. Ear infections are typically treated with 2-8 week course of an appropriate topical medication in the ears. Skin infections are typically treated with a 2-8 week course of antibiotics, anti-fungals and medicated shampoos as appropriate. We can also administer anti-inflammatories, fatty acids and antihistamines to calm down the underlying skin allergy. Specialty diets for environmental allergies can also help greatly.

-Fully addressing the underlying allergy:

Unfortunately, allergies are something we manage, not something we can get rid of completely (in most cases). Many dogs suffer from frequent, recurrent skin and ear infections. This can be very frustrating for dogs, owners and veterinarians alike. For dogs with allergies that are harder to manage, taking more intensive steps to control the underlying allergy is very important. Mild cases can be managed with steroids or steroid-sparing anti-inflammatories, antihistamines and fatty acids. More advanced cases often involve immuno-therapy treatments (a life-long series of injections to desensitize your dog to its main allergens). Advanced food allergy cases involve strict, life-long adherence to a highly specialized home-cooked diet or a veterinary prescription hypoallergenic diet.

Managing canine allergies can be really frustrating, as problems often come back again and again. It takes patience, follow-through and dedication. However, with proper management, we can make a big difference in our itchy dogs' comfort.