Allergy Causes
Allergy symptoms occur when your pet's immune system mistakenly believes a harmless substance (allergen) is dangerous. Your pet's immune system attacks allergens, causing inflammation that triggers allergy symptoms.
Common allergens include:
Fleas
Tree and Grass Pollen
Dust mites
Mold
Mildew
Food
Insect Bites
Bee or Wasp Stings
Shampoos and Cleaning Products
According to UC Davis Veterinary Medicine, the top three causes of allergies in pets are fleas, food, and environmental allergens. Flea allergies happen when the immune system reacts to proteins in flea saliva. Proteins are also the culprit in food allergies. Beef, chicken, dairy, soy and wheat are common allergy triggers in pets.
Have you noticed that your pet's symptoms occur during the spring or fall? Pollen, an environmental allergen, could be the reason.
Common Allergic Reaction Signs and Symptoms
Your pet may be having an allergic reaction if you notice any of these signs or symptoms:
Itching. Allergens inflame the skin, making it nearly impossible for your pet to stop scratching. If scratching breaks open the skin, your pet could develop an infection. Itching often occurs in the ears, paws, belly, skin folds, hind end, face, or head, according to PetMD.
Inflamed Skin. You may notice your pet has a rash or its skin looks bumpy or red.
Hot Spots. Oozing hot spots on the skin may occur if your pet frequently licks or scratches.
Hives. These red welts may appear on the skin during an allergic reaction. Hives can go away on their own in a few hours or might last days in some cases.
Ear Infections. Head shaking or a foul odor from the ears can be signs of an ear infection.
Hair Loss. Licking and scratching may also cause hair loss.
Sneezing, Runny Nose, and Coughing. Seasonal allergies may inflame your pet's sinuses, causing a runny nose, sneezing, coughing, or watery eyes.
Facial Swelling. Facial swelling may be a sign that your pet has been stung by a bee or bitten by an insect. Monitor your pet closely if you notice facial swelling. Severe swelling in the throat or nose may make it difficult for your pet to breathe.
Vomiting and Diarrhea. Allergies can upset your pet's stomach and cause vomiting, diarrhea, or lack of appetite. Vomiting and diarrhea can quickly dehydrate your pet. If vomiting and diarrhea don't improve after 24 hours or are severe, call your veterinarian.
Anaphylaxis. Severe allergic reactions can cause anaphylaxis, a dangerous problem that affects the entire body and may be life-threatening. Symptoms may include pale gums, trouble breathing, restlessness, hives, fatigue, shaking, loss of consciousness, sudden collapse, vomiting, loss of bladder and bowel control, cardiac arrest, weakness, and severe swelling in the face or throat. If your pet shows any of these signs, take your pet to a veterinarian immediately.
How Your Veterinarian Treats Allergies
Your veterinarian must determine the type of allergy before recommending treatments. Your pet's visit to the vet may include skin or blood tests to check for allergies. If your veterinarian suspects your pet is allergic to its food, a food elimination diet may be helpful in discovering exactly what is causing your pet problems.
Elimination diets involve feeding your pet a non-allergenic diet recommended by your veterinarian for a month or two to see if symptoms improve. You'll gradually introduce ingredients that could be causing the allergies one at a time. If your pet develops allergy symptoms, you'll know which types of foods to avoid in the future.
Allergy treatment options include:
Antihistamine or Corticosteroid Medication. These medications reduce inflammation and itching.
Medicated Shampoos. Special shampoos remove allergens and soothe inflamed, itching skin.
Flea Control. Topical or oral flea control products will help your pet avoid flea bites.
Immunotherapy. Immunotherapy, which may include allergy shots or oral medication, exposes your pet to increasing amounts of allergens and gradually decreases sensitivity.
Concerned about your pet's allergy symptoms? Contact our office to schedule an appointment for your furry friend.
Sources:
UC Davis Veterinary Medicine: Allergies in Pets, 8/21/2019
https://healthtopics.vetmed.ucdavis.edu/health-topics/canine/allergies-pets
PetMD: 6 Signs Your Dog Is Having an Allergic Reaction, 4/24/2025
https://www.petmd.com/dog/general-health/dog-allergic-reaction
American Kennel Club: Allergies in Dogs: Signs, Symptoms, Treatments, 4/11/2025
https://www.akc.org/expert-advice/health/dog-allergies-symptoms-treatment/
WebMD: Cat Allergies: Symptoms, Causes, Treatments, Diagnosis, 1/21/2025
https://www.webmd.com/pets/cats/cat-allergy-symptoms-triggers