Just like people, dogs, and cats can be allergic to pollen, dust, and molds. But instead of sneezing and hayfever, pets most often show their allergies in their skin. Allergic cats may develop crusty dermatitis or lick their hair so much that they cause bald spots. Allergic dogs may scratch all over, but especially at their armpits, belly, and ears. They may also have recurrent skin and ear infections and lick their paws. The signs usually start between 6 months to 5 years of age. Since food allergies and skin parasites or infections also cause itching, these diseases need to be eliminated as possible causes of itching before the diagnosis of atopy can be made. Some pets with pollen/dust allergies tend to have seasonal (warm weather) symptoms, while others may have symptoms year-round. Some pollen-allergic pets can be treated symptomatically during the itchy seasons with soothing shampoos/conditioners and anti-itch medications (antihistamines, fatty acids, occasional steroids). If present, secondary bacterial or yeast infections also need to be treated.

Pets with continuous signs or itch that are not well-controlled with symptomatic medications or that need steroids too frequently should be allergy tested to find out what they are allergic to. Allergy testing can be performed with blood tests or skin tests (like scratch testing in people). Blood allergy testing is more convenient and can be performed by most veterinarians, but may be less accurate than skin testing. Skin allergy testing tests the actual organ that is involved in the allergy (the skin), so is more accurate than blood testing and is typically performed by veterinary dermatologists. Once the allergy test results are known, allergic pets can receive allergy shots (just like people!) to desensitize them to the pollen.

Although not a cure or a quick fix, allergy hyposensitization injections help 70-75% of allergic pets to decrease symptoms and need for other medications, and address the cause of the allergies, not just the symptom.

Animals with food allergies can show very similar signs as pets with pollen allergies, but the itching is not seasonal and animals can develop a food allergy at any time in their life—even if they have been eating the same food all along! Cats may develop crusty dermatitis or hair loss similar to pollen allergy. Besides itchiness, food-allergic dogs may also have ear or skin infections. The symptoms of food allergy usually do not improve much with anti-itch medications, and the diagnosis and treatment is to feed the pet a hypoallergenic diet using a protein source that they have never been exposed to before. Switching to another commercial diet usually does not help, because most of these diets have similar ingredients. A better alternative is a hypoallergenic diet with single unique protein ingredients such as fish, rabbit, duck, or venison, with a single carbohydrate such as potato or rice, and no other treats, table scraps, rawhides, milk bones, chewable supplements, or other foods for at last 6-8 weeks. Some food-allergic dogs require home-cooked hypoallergenic diets. Blood or skin testing for food allergy is unfortunately not accurate in dogs and cats, and over-the-counter hypoallergenic diets may have ingredients not listed on the label (Click on this link for more information). If present, secondary bacterial or yeast infections also need to be treated. If the itchy symptoms have resolved in 6-8 weeks, new food allergens can be added one at a time every 2-3 weeks (ie. beef, chicken, lamb, wheat, corn, egg, milk, etc.) to determine what the pet is allergic to and what other foods they may tolerate.