Allergic dog quiz

The technician's role: helping to diagnose an allergic dog

By Kim Horne, AAS, CVT, VTS (Dermatology, Charter Member)

The allergic conditions we see most often in our canine patients are caused by fleas, food, and the environment.  Determining which allergy (or combination of allergies) they are affected with can be a challenge.  These conditions are usually pruritic, which is often the presenting complaint of the owner, especially when the dog is scratching and licking all day and night.  Since allergic diseases are generally chronic conditions that can be controlled or managed, but not cured, obtaining a diagnosis and effective treatment plan is part of the process.  The veterinary technician can be a valuable asset with these cases by collecting a complete dermatological history from the owners, performing dermatologic procedures accurately, and providing thorough client education.

Flea allergy dermatitis

Since flea allergy dermatitis (FAD) is the most common pruritic skin disease of dogs in warm climates, ruling this disease in or out is a first step.   Not all dogs are allergic to fleas, but dogs that develop a hypersensitivity to flea saliva will become extremely pruritic after just a few flea bites.  FAD is related to the duration of flea feeding and the amount of salivary protein injected.  Although any age can be affected, the most common age of onset is three to five years.  Sometimes we are successful at finding the presence of either adult fleas or flea feces on the dog during the physical exam. If evidence of fleas or flea dirt cannot be verified, it is beneficial to institute strict flea control measures to rule this disease out as a differential diagnosis.  Not only can fleas serve as a vector for zoonotic diseases, the dog with FAD can experience much discomfort. It is important to manage any flea problem to reduce pruritus prior to addressing the other allergic conditions.

Atopic dermatitis

While the clinical signs of food allergy and atopic dermatitis (AD) are similar, AD is more common.  The patient’s history may give clues as to which type of allergy the dog may have; for example, an older dog that has never had skin problems before may be more likely to have food allergies. Similarly, a seasonally affected dog is more likely to have AD with environmental pollen allergies. For the dog that is affected year-round, the owner may wish to perform an elimination diet trial to rule this disease in or out before pursuing allergy testing for AD. Occasionally, some patients will have a combination of both food allergy and AD.

Food allergy

Food allergy is an allergy to one or more ingredients in the dog’s diet, typically to something they have been eating for a while.  It is generally a non-seasonal condition (provided the dog eats the same diet throughout the year) and may be seen in very young dogs or older dogs that have never had skin problems before.  Performing a strict elimination diet for 8-10 weeks can be challenging and expensive for the client, especially when small children or other pets are present in the household.  A complete diet history will help the veterinarian with their recommendation for a prescription diet to use for the trial.  Nothing else should pass the dog’s lips during the trial: chewable medications should be switched to non-chewable, and non-flavoured toothpastes or chew toys should be used during the trial.

More about AD

AD has a complex pathogenesis and is estimated to occur in 3-27% of dogs. After environmental allergens such as dust, pollens, and moulds are absorbed (via the respiratory tract, oral mucous membranes, or skin), an inflammatory response of the immune system can occur.  AD can be either a seasonal or non-seasonal condition depending on what the dog is allergic to.  Dogs may start out with seasonal problems and progress to year-round allergies.  Symptoms often begin when the dog reaches one to three years of age.  Although they can start showing signs as early as 6 months, it is unusual to diagnose this disease in dogs older than 7 years of age. AD is suspected to be a genetically predisposed disease; therefore intact allergic dogs should not be bred.  Although there is no diagnostic test to verify AD, the diagnosis is made based on the patient’s history and after ruling out other causes for the dog’s pruritus.  Allergy testing (intradermal or serum) is used to identify which environmental allergens should be considered for either avoidance (often impractical) or therapeutic (allergen specific immunotherapy). Also important to note is that dogs with AD may be more prone to develop flea allergy.  Moreover, other environmental and dietary factors may play a role in potentially affecting the development of AD, such as puppies being born during the allergy season.  It has also been speculated that foods may be a flare factor for dogs with AD.

The technician’s role

The technician can play an important role by creating a dermatology history questionnaire to use in their practice.  This can be an efficient way to collect important information by having the client fill out the questionnaire prior to the appointment. This will often get the client thinking about their pet’s skin and/or ear problems.  Examples of important questions to ask these owners are:  Is your dog itchy?  When did they first notice the problem and how has it changed over time?  Have any diagnostic tests been performed?  What medications/treatments have been tried (including topical and over the counter products)?  What has helped and what hasn’t?  What is the pet’s diet (including treats)?  Is this a seasonal or non-seasonal problem and if year-round, are there any seasonal exacerbations?  Are there other pets in the household and if so, are they showing similar signs?  Are any humans in the household affected? 

Ask open-ended questions (e.g. “Please describe any scratching, licking or chewing behaviour you’re noticed with Fluffy” instead of “Does Fluffy itch?”) and allow the client to share the chronological sequence of events. The client with the most knowledge of the dog’s condition should be present for the exam.  Appointments for dogs with skin and ear problems should be longer to allow sufficient time to collect the complete history, perform any recommended diagnostic tests, and then to educate the owner to ensure client compliance.  Good communication and listening skills on the part of the technician are essential.  The information collected can help the veterinarian decide which allergy is more likely, and help to pinpoint which diagnostic tests should be performed. All of the information will hopefully help to determine a diagnosis and treatment plan sooner for the patient.

Kim is a certified veterinary technician and works at the University of Minnesota, Veterinary Medical Center, of which the last 26 years has been devoted to the dermatology service. She is a member of Minnesota Association of Veterinary Technicians, National Association of Veterinary Technicians in America, and American Academy of Veterinary Dermatology.  Kim is a charter member of the Academy of Dermatology Veterinary Technicians and the current President.  She is currently working on a dermatology book for veterinary technicians and nurses.

This article is based on Ms. Horne’s presentation at the North American Veterinary Community Conference in Orlando, FL.CVT