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Your Itchy Dog

Ryan Olexia, DVM

Imagine the sleepless nights for your pup (and yourself) as he/she chews away at their paws or scratches relentlessly at their ears!  Most pet owners have suffered through skin itching, or “pruritus,” at some point or another.  This article will inform you about the potential causes, preventions, and treatments of this common problem.

There are 2 broad categories of potential causes: Primary Skin Infections and Allergies.  The most common type of primary skin infections are flea infestation, sarcoptic mange, ringworm (less itchy) and demodectic mange (less itchy) to name a few.  These external infections can be observed during the physical exam, with microcopy, or identified with skin cultures.  Sometimes we can identify the organisms with the microscope but other times we need to use clinical signs, history, breed, culture results and response to treatment to make a presumptive diagnosis.  If we can rule out primary skin infestations we then proceed to the next potential cause of the itching - allergies.

Allergies are basically an exaggerated immune response or “hypersensitivity” to a naturally occurring substance in the environment or food.  The substance causing the immune response can be identified as an “allergen” or “antigen”.  Allergens/antigens can be anything from tree/grass/weed pollens, mold spores, dust mites, animal protein, or flea saliva.  Skin allergies in dogs are often compared to “Hay Fever” in people that cause respiratory signs (asthma, itchy eyes, runny nose).  In dogs these allergies usually manifest as itching, redness, recurring ear infections, or hair loss. It is also common to have secondary bacterial or yeast infections.   There are basically 3 types of skin allergies: Flea Allergy, Food Allergy, and Environmental Allergy (Atopy).

Flea allergy is not truly an allergy to contact with the flea but specifically the saliva of the flea.  When the flea takes a blood meal from your pet the saliva is absorbed and the immune system recognizes the saliva as an allergen, causing an exaggerated immune response and pruritus.  A flea allergy usually presents with the “pants down” pattern of itching or hair loss - primary areas affected are the lower back, abdomen, and the legs.  

There are a couple of facts about flea allergies that are a bit misunderstood:

  1. You do not have to see fleas for your dog to be itchy from fleas.  All it takes is a single bite from a single flea for your dog to become itchy.
  2. Fleas are not seasonal; fleas can bite during all seasons of the year.  Although the number of fleas may decrease in the outdoors small numbers persist in the home year round.

If a flea allergy is suspected we recommend monthly flea prevention (Frontline, Revolution, etc) year round. At a minimum, 4 consecutive months of treatment is needed to kill all live fleas and those that hatch from eggs in the environment over the following 3 months.

Food Allergy is an exaggerated immune response to proteins, carbohydrates, and (less commonly) grains such as beef, chicken, pork, corn, wheat, or soy.  This type of allergy is typically year round, and can spontaneously occur even if your pet has been on the same diet for years, or if you switch them to a new diet.  If this type of allergy is suspected we recommend a 6-8 week long food trial with a diet composed of protein/carbohydrates your pet has never seen  - for example, duck and sweet potato or venison and sweet potato.  While completing the food trial it is imperative that no other protein/carbohydrates are ingested since even the smallest amount of the allergen can cause the itchiness to continue.  If there is no improvement in the itchiness after 6-8 weeks we will consider another type of diet or decide that food is not the cause of the allergy and proceedto the next possible cause.  If there is a nice improvement with the food trial we will most likely continue the new diet indefinitely as a treatment of the problem.

Atopic Dermatitis is the 3rd type of skin allergy.  This type of allergy is usually seasonal. This basically is an allergy to one or multiple compounds that can occur in the environment, such as pollens, dust, mites, spores, or animal dander just to name a few.  This can be a diagnosis of exclusion (by ruling out the flea allergy and food allergy) or by completing allergy testing.

With any of the 3 types of allergies secondary skin or ear infections with bacteria or yeast can occur.  Typically upon the first appointment for skin problems your pet will be placed on antibiotics and topical shampoos to treat the secondary infections so we can focus on the underlying cause after the infection is cleared.

At this point there is no “cure” for allergies, but there are treatments and management that can be utilized to improve the pet (and owners) quality of life.  For Food Allergies, the new food with the novel protein and carbohydrate is the treatment. For Flea Allergies we recommend strict monthly topical flea prevention.  Atopic dogs usually need a combination of topical and oral therapies.

There are a wide range of oral medications that may be prescribed to help calm the itching.  Steroids and antihistamines are the first line oral medications to calm the itch.  Steroids (prednisone, dexamethasone) are hugely effective but can only be used for short periods of time due to the negative side effects of long term use.  Antihistamines (Benadryl, Hydroxyzine, etc) are safe but used alone may not calm the symptoms enough.  A new medication on the market, Apoquel, is very effective and prevents the itch by inhibiting mediators that cause it.  Although effective and safe, the supply of Apoquel has been very limited and may not be dependably available for years.  Atopica is another effective medication that inhibits the body’s “allergic reaction” to the allergens.  In my experience approximately 50-60% of patients on Atopica show improvement. The biggest downsides of this medication are the cost and the transient gastrointestinal upset that occurs when starting it. 

Many dogs that suffer from skin allergies have a combination of the 3 primary causes; for this reason it may be unrealistic to hope that we can permanently cure their itchiness.  The goal of long term therapy is to reduce the severity of the symptoms and maintain a healthy quality of life for pet and owner.  For most owners the best way to manage or prevent severe skin itching is sticking to a consistent high quality diet and year-round monthly flea prevention with products like Vectra, Trifexis, and Revolution.  If you have any questions about allergies, flea treatment or dietary choices please feel free to contact us!

Originally published here.