Itching and Allergy in Dogs

Coping with an itchy pet can be an extremely frustrating experience for you, the pet owner and can truly test the limits of the human-animal bond.  Persistent scratching and chewing by the pet can also result in self-excoriation and open wounds.  The following information is intended to provide the pet owner with a basic understanding of the most common underlying causes of itching and allergies in the small animal.

The Most Common Causes of Chronic Itching:
The common causes fall into two groups: external parasites and allergies.  External parasites that most commonly cause chronic itching dermatitis include fleas and sarcoptic mange.  We often recommend therapeutic trials for sarcoptic mange in chronically and severely itchy dogs.  We always recommend stepped-up flea control and monitoring for fleas, as flea infestation can really make allergic dermatitis much worse!

What are allergies?
Allergy is a state of hypersensitivity in which exposure to a harmless substance known as an allergen induces the body’s immune system to “overreact”.  The incidence of allergies is increasing in both humans and their pets.  People with allergies usually have “Hay Fever” (watery eyes, runny nose and sneezing) or asthma. While dogs can rarely also have respiratory allergies, more commonly they experience the effects of allergic hypersensitivities as skin problems.  Though there are a variety of presentations, this can often be seen as redness and itching, recurring skin or ear infections, and hair loss.  This is sometimes called ‘eczema’ or atopic dermatitis.  

What are the Major Types of Allergies in Dogs?

Flea Allergy
Flea allergic dermatitis is the most common skin disease in dogs and cats.  For the flea allergic patient, 100% flea control is essential for the pet to remain symptom-free.  “But doctor, I never see fleas on my pet.”-   You may not see them, but that does not mean they are not there.  The allergy is caused by the flea’s saliva, and a limited number of bites may induce the problem.  Also, the itchy pet often scratches so much that adult fleas are removed, making them hard to find. Because flea allergy is so common, we recommend that complete flea control be instituted before proceeding with diagnostics for other allergies and that year-round flea control be maintained for all allergy patients.

Food Allergy
Some pets develop specific hypersensitivities to components of their diets.  The most common food allergens in dogs are beef, poultry, dairy, and wheat.  In cats, beef, chicken and fish are most commonly implicated. Minor ingredients such as preservatives or dyes are also potential allergens.  The diagnosis of food allergy requires that we test your pet by strict feeding of a hypoallergenic diet. This is often achieved by feeding a prescription diet for a period of 8 - 12 weeks.  If the signs resolve, a challenge is performed by feeding the former diet and watching for a return of the itching.  If this occurs, a diagnosis of food allergy is confirmed.  There are laboratories who offer food allergy blood and saliva tests, but these are highly discouraged as there is no evidence of scientific validity. 

Atopic Dermatitis
Atopic dermatitis (AD) is a multifactorial frustrating disease involving genetics, immune dysregulation and skin barrier function defects that predispose the patient to develop allergies from exposure to variety of commonplace and otherwise harmless substances including the pollens of weeds, grasses and trees, as well as house dust mites and mold spores.  The diagnosis of AD is made based on the classic clinical signs. The results of intradermal skin testing or in vitro blood testing may be used to identify environmental allergen triggers for the affected individual. Please note that not every patient with AD has allergies. 
  
Secondary Infections
Allergies are often the underlying cause of recurring skin and/or ear infections.  Bacterial and yeast infections, though secondary to the allergy, can cause an increase in your pet’s level of itching. Treatment with oral and topical antimicrobials is often required. Given increasing concerns for the development of antibiotic resistance, dermatologists usually emphasize topical therapies whenever possible.

Can allergies be cured?
Unfortunately, there is no cure for allergic disease and it is usually a life-long problem. We seek to control allergy and improve the quality of life for both you and your pet.  We will formulate the best program of management that suits all involved with your pet’s care.  

Will diagnostic allergy testing mean I won’t have to give me pet medications?

Diagnostic testing is not a replacement for symptomatic therapies. The goal of allergy testing is to try to reduce the amount of medication required, but it is not a substitute. Symptomatic therapies are always the main focus in managing allergic disease, as long term therapy is usually needed.  Steroids are appropriate for short term use if needed, but long term use of steroids can result in many health problems.  This is the reason that we encourage diagnostic testing and more specific and less potentially harmful treatments. The development of more targeted symptomatic therapies like cyclosporine, Apoquel (oclacitinib) and Cytopoint (lokivetmab) has made long term relief of clinical signs possible with less chance of adverse side effects than the use of steroids.