What is Allergic Dermatitis in Cats and Dogs?
on May 28, 2015
Posted in Cats
Allergies are hypersensitive immune responses to substances that either come in contact with or enter the body. Dermatitis is inflammation of the skin. Most allergic reactions in dogs and cats manifest as dermatitis.
What Types of Allergies Cause Dermatitis?
Allergic dermatitis is commonly caused by the following conditions in dogs and cats:
- External parasites such as fleas, ticks, mites, or lice.
- Fleas are the most common parasite that cause allergies in pets, but the others can be a problem as well. They can also cause issues for the people in the home.
- Inhaling or contacting substances in the environment, including dust mites, pollen from grass, flowers, or weeds, or molds.
- While inhalant allergies most often cause humans to develop runny eyes and a stuffy nose, pets are much more likely to develop pruritic (itchy) skin.
- Food components.
- Food allergies are very common in pets and can affect them at any age. New foods can cause a problem, but more often an allergy is developed to a food that the pet has been eating for a long time.
- Bacterial, yeast or fungal infections. Infections with these organisms can occur due to a genetic problem with the skin barrier or secondarily to another allergy. As the pet’s skin becomes inflamed and irritated due to the allergy, the normal bacterial and yeast inhabitants of the skin may overgrow, worsening the problem.
Signs of Allergic Dermatitis
If you notice any of the following problems with your dog or cat’s skin, allergic dermatitis could be the culprit:
- Pruritic (itchy) skin, feet, or ears. This usually manifests as chewing, licking, and/or scratching these areas.
- Scabs and bumps on the skin. These could be secondary to the trauma to the skin caused by the pet’s mouth and nails or it could indicate that the skin is infected.
- Foul odor. An allergic pet may develop a bad odor from the skin.
- Changes in skin color and texture. Skin affected by allergic dermatitis often darkens and thickens over time.
- Hair loss. Excessive hair loss beyond normal shedding indicates some issue with the skin. Some areas may become entirely bald.
- Frequent head-shaking. The ears are a common body part to be affected by allergic dermatitis. Animals may shake their heads or scratch at their ears excessively due to itchiness, and secondary infections may also develop that worsen the issue.
- Fur-staining. When an animal’s saliva has prolonged contact with an area of fur, that fur will often turn reddish-brown.
Diagnosis of Allergic Dermatitis in Dogs
Your veterinarian will do a thorough physical examination on your pet if he or she suspects allergic dermatitis. Before doing other tests, your doctor will want to rule out fleas allergy because it is the most common cause of itchiness in dogs and cats. After that, there are multiple tests, some or all of which may be employed to diagnose the problem:
- Skin cytology: A sample of the cells on the affected area of skin may be collected and examined under the microscope. This can determine whether there is an excessive amount of bacteria or yeast present.
- Skin scraping: For this test, a scalpel blade is used to scrape cells and debris from the affected skin. This material is placed on a microscope and examined for the presence of mites, such as sarcoptes, cheyletiella, and demodex.
- Skin culture: This test is done when a bacterial or fungal infection is suspected. A sample of debris from the lesion is collected and the bacteria or fungus is grown on a petri dish in the lab. It can then be identified and challenged with different antibiotics to determine which ones will be effective.
- Blood allergy testing: Blood samples from the pet can be sent to a lab where they can be tested to determine whether the pet is allergic to various substances. Blood testing is more reliable when testing for environmental allergies than food allergies.
- Intradermal skin testing: This test, similar to one performed in humans to diagnose allergies, involves injecting tiny amounts of different allergens into the pet’s skin, then watching for a reaction that would indicate that the body is overreacting to it.
- Elimination diet: If food allergy is suspected, it can be diagnosed through the use of an elimination diet. A special diet is given to the pet for 12 weeks. No other food, treats, flavored medications, or toothpastes may be used during the testing period. If the pet’s skin signs clear up near the end of the time period, food allergy may be diagnosed. There are two types of diets commonly used for elimination trials:
- Because the protein source in a diet is most often the trigger for the allergy, a novel protein diet uses a protein source that the pet has not been exposed to before. The carbohydrate sources in these diets are often novel as well.
- A hydrolyzed protein diet is a commercial prescription diet in which the protein source has been broken down to be so small that the pet’s body doesn’t recognize it in order to trigger an allergic reaction.
Treating Allergic Dermatitis in Pets
Treatment of the allergic dermatitis depends on the cause:
- Parasites: All pets in the house must be treated for the parasite as the first step. Ridding your house and yard of fleas and ticks and using an appropriate preventative on all of the pets in your home will be necessary for long-term management of the allergy.
- Food allergy is treated in one of two ways: you may continue the original elimination diet or you may challenge that diet with various foods to see if the signs of allergy return. In this way, you may be able to expand the list of foods that you can give your pet.
- Environmental allergies: Immunotherapy may help many pets with inhalant allergies. Small amounts of the allergenic substance are formulated into allergy injects that are given under the skin to the pet. Over time, the pet’s immune system responds more appropriately to that allergen.
- Infections: All infections regardless of cause must be treated before the pet’s signs will improve. Topical and/or oral products may be used to treat these infections.
- Symptomatic care: There are many conventional and natural treatments that can aid in controlling the itchiness that your pet experiences during an allergy flare-up. These include cool baths, sprays, shampoos, and conditioners. Antihistamines or prednisone may be recommended to control the allergic reaction and decrease the associated signs. Atopica, an immunosuppressive medication, is used in some pets that need long-term allergy control. In the U.S., Apoquel is a new pharmaceutical for allergic dogs. It acts differently than steroids and Atopica but still causes immunosuppression.
Alternative Treatments for Allergic Dermatitis
Holistic treatments for allergies in pets include acupuncture, herbs and homeopathy. The foundation of all holistic treatment is diet. A good home-prepared diet that is properly balanced is very important for controlling your pet’s skin condition. Other supplements such as Omega 3 fatty acids, turmeric, and Pet Wellbeing’s Itch Support Gold and Derma Gold can also be helpful for these itchy pets.
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Janice Huntingford, DVM, has been in veterinary practice for over 30 years and has founded two veterinary clinics since receiving her Doctor of Veterinary Medicine at the Ontario Veterinary College, University of Guelph. She has studied extensively in both conventional and holistic modalities. Ask Dr. Jan