Does your dog scratch himself excessively? Does he gnaw at specific parts of his body or rub his face? Does he lick his paws compulsively? If this is the case, he may suffer from allergies. Our pets can also suffer from allergies. However, the symptoms are usually dermatological and sometimes respiratory as opposed to humans where the symptoms are usually respiratory. Sometimes the itch is so intense that the animal creates wounds that can eventually become infected.

But what are allergies? An allergy is a reaction that occurs subsequent to the exposure to substances normally found in the environment or food. The substance that causes this reaction is called an allergen. Allergens may include, among others, pollen, mold, animal hair, dust, fleas or certain ingredients in food. When the animal comes into contact with this substance, either by direct contact, ingestion or through respiration, his antibodies will release biochemical substances that will cause the symptoms mentioned above. They may only come about seasonally if the animal is allergic to pollen for example, or be present year-around when the problem is related to food (there is usually vomiting and diarrhea in addition to the dermatological symptoms) or domestic substances like dust or mites.

Once the diagnosis of an allergy is made by the veterinarian, he may choose an empirical treatment with corticosteroids, immunosuppressors, antihistamines or a combination of these medications. We usually proceed this way when it is the first episode of allergies (which can occurs at any time during the life of the animal) or when the symptoms are seasonal and the animal only needs treatment for a short period of time each year. However, sometimes, it is preferable to know the allergens responsible for the symptoms in order to eliminate it, when possible, from the environment. Corticosteroids, which are often used to limit the itch, can have some undesirable side effects in the long term and therefore it may be beneficial for your pet to identify alternative treatments. The side effects may include renal or liver damage, diabetes, Cushing's disease or even extreme thinning of the skin. When the patient is weaned from this medication, the dermatological condition can improved.

There are two ways to identify the allergens. The first one consists of injecting the patient, subcutaneously and under general anesthesia, very small quantities of different environmental allergens and observe the appearance of characteristic signs of inflammation which can be redness, inflammation and pain at the injection site. However, it is not possible to use this method to identify food allergens. The other method consists of sending a sample of blood from the patient to a laboratory that will determine the number of antibodies present against multiple environmental and food allergens. If an elevated number of antibodies against an allergen is found, it can be concluded that that the animal is allergic to this allergen.

It is important to know that the worth of the serological (blood) test is controversial. Some veterinary dermatologists don't believe in this method while others remain undecided. In fact, these specialists prefer the injection method because the reaction is directly visible whereas the serological test only evaluate the number of antibodies present. In addition, with this test, there are often false positives when it comes to food allergens, which means that the test confirms that the animal is allergic to a substance when in fact, he is not. However, as previously mentioned, the injection method cannot be used for food allergies. Other inconveniences with the injection method that may make one lean toward the serological test is that it must be done under general anesthesia, the patient must not receive immunosuppressors 2 to 3 weeks prior (whereas we can continue the treat with the blood test) and that skin reaction can sometimes be difficult to interpret. It is for this reason that we usually refer the patient to a dermatologist when we choose the injection method.

Once the allergens have been identified, the best way to solve the allergy problem is to eliminate the allergen(s) from the animal's environment. However, since this is usually impossible, the alternative is to desensitize the patient. This consists of injecting the animal, at fixed intervals, beginning with very small doses and concentrations and increasing gradually, the allergen(s) in question with the goal of developing a tolerance toward them so that the animal no longer reacts when he is exposed.

The mechanism by which this tolerance is developed is the following: the antibodies responsible for creating such reacts are called IgE. As the dose of the allergen administered increases, another type of antibody, IgG, increases at the same time. The role of these IgG is to prevent the allergens that enter the body from reaching the IgE. As a result, the IgE do not release the substances responsible for the allergy symptoms. When the quantity of IgG reaches a certain limit (this varies individually), the animal should no longer react to the causal allergens.

The rate of success for desensitization is approximately 75%. This means that 25% of dogs will continue to require traditional treatment (possibly at reduced doses) to control the symptoms. Some animals will only require injections for a certain period, but most of the time it is a lifelong treatment. Given that the medication is only efficient within 3 to 5 months, it is necessary to continue the injections at the beginning and then gradually wean the patient.

Adverse side-effects to desensitization are extremely rare, generally temporary and do not put the patient's life at risk. An exception is when we increase the concentration of the allergen. At this time, anaphylactic shock is possible, meaning that the massive release of substances in the organism that cause any of the following symptoms: excitement, severely itchy skin with lesions, inflamed face, vomiting, diarrhea, difficulty breathing, salivation and collapse. This is why we recommend to give doses coming from a new vial at the clinic and to keep the animal under veterinary surveillance for an hour following the injection so that we are able to intervene immediately if need be.

Unfortunately, with regards to food allergies, it is not possible to desensitize the animal. It is therefore necessary to eliminate the ingredient to which the animal is allergic either by creating a "house blend" at home or by using a commercial hypoallergenic food that does not contain the allergen.