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Allergies in Dogs

Allergies in Dogs

by DR. SHERI SIME on MARCH 21, 2011 in ARTICLES (updated November 20, 2013)


Recurrent skin and ear inflammation and secondary infections are common manifestations of allergies in our pets.  Like people, they often have not just one, but a number of allergies and it is often substances that cannot be eliminated from their environment.  Although we cannot "cure" allergies, our aim is to manage them to maintain comfort.  This is often accomplished by combining different treatment regimes to minimize side effects of each and maximize combined benefits.  It has been my experience that pets first manifesting symptoms of allergies when under one year of age, become amongst the most challenging to control.  It is thought that symptoms become apparent after a certain threshold of allergy exposure is obtained.  Animals may have a food allergy, not being itchy, but when exposed to another allergen, they show symptoms.  A pet with a food allergy component may hence show seasonal clinical signs of itchiness despite being exposed to a food year round.

Allergies can be inherited; an affected pet should not be bred.

Inhalant Allergies

Pollens, dust mites and molds are included under airborne allergens.  Pets affected by inhalant allergies may present with chewing, scratching, licking and biting of their feet, flanks, groin and armpits areas.  Although we can not eliminate most of these substances from their environment, we can limit their exposure.  Using the air conditioner, to keep windows closed, installing an air cleaner, removing rugs, and using dehumidifiers to maintain relative humidity between 30-50% all help.  Regular bathing of pets, and  regular vacuuming are also helpful.  Plants should be removed if your pet has a mold allergy.  If not removed, cover the soil with activated charcoal bits (aquarium supplies) to prevent mold growth.

Food Allergies

An animal does not have to be exposed to a new food to suddenly develop allergies; they may develop symptoms from products that they have been exposed to for years.  Symptoms of food allergies include biting, licking and chewing of the feet, face or ears and the development of "hot spots".  Recurrent ear infections are often a manifestation of underlying allergies.  Some animals with food hypersensitivities will also present with gastrointestinal symptoms including diarrhea, vomiting, and flatulence.  In extreme cases they may experience seizures.

Pets with a food allergy may be below the threshold for showing symptoms, but when another antigen is present, the animal becomes clinical (outward signs). Hence pets, even with seasonal allergies, may have a food allergy component and benefit from these prescription hypoallergenic diets.

Most of the commercially available diets have similar ingredients, so it is not uncommon to have them react to more than one diet.   Common food allergies for dogs include chicken, beef, pork, milk products, eggs, soy, wheat, and preservatives.   In cats, common allergies include beef, milk products and fish. As more and more commercially available diets have turned to alternative protein sources, what was once considered hypoallergenic or a novel protein source is now commonly found in many diets and will not help a pet with a food allergy.  For instance Lamb and fish are no longer novel proteins for many pets.  Commercially available lamb and rice or "hypoallergenic" diets can contain chicken, soy, and wheat, etc., so please read the label.

If a pet has eaten an ingredient to which they react, the response can be seen for upwards of 3 months.  I have had a patient with recurrent ear infections develop approximately 48 hours after the consumption of facial tissue. If a pet is placed on a prescription or homemade "hypoallergenic" diet, it is critical that nothing else is fed to them during the initial 3 month

trial period including people food, treats, and some oral heartworm medications (use an alternative).  Nothing should be fed with medications given.

Novel ingredient prescription hypoallergenic diets, and hydrolyzed protein prescription diets are now available. The latter types of diets are often used during a food trial to determine if a pet has a food allergy component to their symptoms. Approximately 80% of dogs with food allergies will respond to prescription hypoallergenic diets.  These diets will also contain anti-inflammatory elements.

Ultimately a homemade diet which contains novel products could be fed in those that do not respond to any of the commercially available hypoallergenic diets.  These diets are not meant for long-term feeding as they are not nutritionally complete. These trials start with a starch (potatoes or rice) and a novel protein source (rabbit, deer, kangaroo, moose) in a ratio of 2:1.  The ingredients are boiled and fed during a SHORT term trial. Then individual ingredients are re introduced on a weekly basis.  When symptoms recur we have likely identified an allergy inducing ingredient. We then ultimately try and find a diet which does not contain these ingredients.

Note blood and skin testing for food allergies is not reliable.

Flea Allergies

Dogs which have an area just above their tail base with alopecia (hair loss) and pruritis (itching) are often pets affected with flea allergies.  The symptoms occur long after the flea has left the area. When biting fleas inject saliva into the skin to which the patient reacts.  This reaction will carry on for up to a week. Flea prevention is the key.


Skin allergy testing involves shaving a pet and injecting various antigens and measuring the immune system's response.  The identified substances creating an excessive immune response are then formulated into a series of injections to be administered over six to eight months.  The aim is to try and fatigue the immune response to these substances.   Dermatologists report about a 75% response rate to immunotherapy.  When skin testing is not possible, blood testing may be designed to identify allergens, however the accuracy of these results is questionable.  Skin allergy testing is a referral procedure.  Prior to the appointment with the veterinary dermatologist, it is important that all steroid-containing topical skin, eye and ear products are stopped, which can influence the skin reaction results.

Management options:

Pets should be under the direct supervision of a veterinarian.  They will provide individualized recommendations on what would be the safest and most effective treatments for your pet.

Topical products

Topical sprays some with witch hazel and others with low levels of corticosteroids have been used for a short term on localized spots.

Bathing in cool water with medicated shampoos

Cool water bathing with medicated shampoos offer temporary relief. The shampoos will help to relieve itchiness. Some are sulphur/salicylic based (Sebolux), chlorhexidine (Hexadene), or oatmeal based (Epi-Soothe).  Skin may then need to be moisturized with cream rinses or sprays (humilac, epi-soothe).  Please note a hypoallergenic shampoo is indicated for skin sensitive pets, not for those pets with an allergy.


Approximately 30% of dogs will have a reduction in itching.  If one antihistamine does not offer any relief, another should be tried.  Sedation is a common side effect.  My preference is hydroxyzine for dogs, chlorpheniramine in cats.

Prescription Omega 3, 6 Fatty Acids

Fatty acids can improve symptoms in patients and have few side effects.  Their anti-inflammatory benefits  not only help skin inflammation, but arthritis too. They alone are not expected to control an allergy, but are often used in combination with other therapies. Products such as Derma Caps, EFA z plus, etc. help about 20% of patients. These products differ from the commercially available fatty acids to improve the coat quality. They should be used with caution in pets with a history of or breed predilection towards pancreatitis (i.e. Schnauzers).


These can offer a pet relief from the itching, but can have side effects throughout the body.  When used, we try and combine them with other treatment modalities, and find the lowest possible alternate day dosing that will maintain a pet's comfort. Common side effects include increased urination and appetite, and some pets will experience behavioural changes.  Long term use of corticosteroids can lead to the development of diabetes, immunosuppression, or Cushings disease. Safer products, with a lower dose of corticosteroids combined with antihistamines (Vanectyl-P) are commonly used.

Immune Modulators

Cyclosporin (Atopica) has offered pets comfort when other regimes have not.  Side effects can include vomiting and diarrhea when initially started, and possibly skin growths and gum hyperplasia (overgrowth).  They are contra-indicated in patients with tumors.

Allergies remain one of most costly and frustrating diseases for a pet.  We are unable to cure allergies, but with proper steps taken, they can be well managed and your pet can enjoy a high quality of life.