February 12, 2016

It's Spring and My Pet Itches! A Look at Seasonal Allergies

The most common allergies in dogs and cats fall into 3 categories: atopy (allergy to substances in the environment), flea allergy, and food allergy.
By Laurie Anne Walden, DVM, ELS
Dogs and cats can be allergic to the same things that make people sneeze. Unlike allergies in humans, however, allergies in small animals are more likely to affect the skin and ears than the respiratory system.1 Symptoms of allergies in dogs and cats can include the following: 
  • Itchy feet
  • Itchy face
  • Reddish-brown discoloration of the feet (from saliva staining)
  • Red skin, especially on the abdomen, legs, or armpits
  • Smelly or itchy ears
  • Hair loss
  • Scabs, crusts, or bumps on the skin
  • Conjunctivitis2,3
The most common allergies in dogs and cats fall into 3 categories: atopy (allergy to substances in the environment), flea allergy, and food allergy. Some pets have allergies in more than one category.
 
Atopy
Atopy is a hypersensitivity to environmental particles that are inhaled or absorbed through the skin.3 Atopy is often seasonal but can be year-round, depending on the cause. Skin testing, usually performed by a veterinary dermatologist, can identify the specific allergens that cause reactions in a pet with atopy. Triggers may include these common causes: 
  • Pollens, especially from trees and grasses
  • Mold
  • House dust
  • Dust mites
  • Other animals (dander)1,4
Atopy has a genetic component and is often seen in terriers and retrievers, although any dog can be affected. Animals with atopy typically start showing symptoms at a young age: under 3 years in dogs and under 5 years in cats.2,5 In dogs, licking the front feet is a classic sign of atopy. Cats with atopy, however, are often itchy around the head and neck and may develop small scabs anywhere on the body.3
 
Flea Allergy
Animals with a flea allergy have an intensely itchy reaction to the bite of even a single flea. Because flea-allergic pets groom themselves excessively in response to the itching, few or no fleas may be visible on the skin. Flea allergy symptoms can be seasonal or year-round, depending on the climate; the peak is often in the late summer or fall.
 
Food Allergy
Food allergies are less common than atopy but can cause similar symptoms in dogs and cats, although the symptoms are not seasonal. Pets can become allergic to any ingredient they have eaten in the past; common culprits are beef, chicken, eggs, and corn. The only way to diagnose a food allergy is by feeding an elimination (hypoallergenic or novel ingredient) diet and watching for symptoms to resolve. It is best to consult a veterinarian before planning a diet trial.2
 
Secondary Infections
Dogs and cats with allergies commonly develop secondary skin infections caused by bacteria, yeast, or both. These infections can also be very itchy, and allergy treatment alone will not make a pet comfortable until a skin infection is under control. An ear infection is sometimes the only sign of an underlying allergy and may not be noticed by the owner. Signs of a skin infection can include the following: 
  • Scabs
  • Raised bumps
  • Crusts
  • Redness
  • Odor
  • Thickened skin1
Treatment
An allergy is a chronic condition that can get worse over time, so it’s best to seek veterinary care early. Any pet with itching or other symptoms that do not respond fairly quickly to home care should be seen by a veterinarian. Home care can include the following: 
  • Use flea control for all dogs and cats in the household (both indoors and outdoors). Depending on the climate, this could mean treating all year long. Prescription flea products have made flea control much easier than it once was; talk to your veterinarian.
  • Bathe your pet with a mild pet shampoo. This removes allergens from the coat and can provide some relief from itching. An oatmeal-based shampoo is often a good choice. Do not use OTC medicated shampoos without first consulting your veterinarian because some of them can irritate the skin.
  • If you know your pet’s allergy triggers (from skin testing, for instance), reduce exposure as much as possible. For example, vacuum often and use a HEPA filter if your dog or cat has a dust mite allergy. 
Your veterinarian may perform diagnostic tests to identify skin and ear infections and rule out diseases that mimic the symptoms of allergies. The treatment plan depends on the diagnosis and clinical signs and can vary over a pet’s lifetime. Treatments prescribed by your veterinarian may include the following: 
  • Medicated shampoos, conditioners, sprays, or other topical agents
  • Antihistamines
  • Antibiotics
  • Antifungal drugs (for yeast infections)
  • Fatty acid supplements
  • Short-acting corticosteroids
  • Immune-modulating drugs, such as cyclosporine
  • Immunotherapy injections (allergy vaccines individualized for each patient)3
Your pet might also benefit from referral to a veterinary dermatologist. Dermatologists can formulate allergy vaccines based on skin test results and also have access to new treatment options like monoclonal antibody therapy. An allergy is a lifelong condition that cannot necessarily be cured, but with your veterinarian’s help, it can usually be managed.
 
Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University in 1994. After an internship at Auburn University College of Veterinary Medicine, she returned to North Carolina, where she has been in companion animal general practice for over 20 years. Dr. Walden is also a board-certified Editor in the Life Sciences and owner of Walden Medical Writing. 

References:
1. Allergies. Texas A&M Veterinary Medical Teaching Hospital website. www.vethospital.tamu.edu/small-animal-hospital/dermatology/allergies. Accessed January 9, 2016.
2. Allergies in dogs. The Merck Manual: Pet Health Edition website. www.merckvetmanual.com/pethealth/dog_disorders_and_diseases/skin_disorders_of_dogs/allergies_in_dogs.html. Updated June 2011. Accessed January 9, 2016.
3. Hnilica KA. Small Animal Dermatology: A Color Atlas and Therapeutic Guide. 3rd ed. St Louis, MO: Saunders; 2011.
4. Netherton S. Dogs’ itchiness may indicate atopic dermatitis. University of Illinois College of Veterinary Medicine website. www.vetmed.illinois.edu/pet_column/dogs-itchiness-may-indicate-atopic-dermatitis/. Published October 28, 2013. Accessed January 9, 2016.
5. Allergies of cats. The Merck Manual: Pet Health Edition website. www.merckvetmanual.com/pethealth/cat_disorders_and_diseases/skin_disorders_of_cats/allergies_of_cats.html. Updated July 2011. Accessed January 9, 2016.
 

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