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Scratching at the Surface of Canine Skin Allergies

You recognize your dog’s excessive scratching, licking and chewing at his or her skin for what they are — signs of allergies. But do you know what’s actually causing your pet’s allergies?

Allergens are otherwise harmless substances such as pollen, mold, dust or food proteins that cause the immune system to overreact in sufferers. Your veterinarian can narrow down which of these substances are triggering your dog’s signs and symptoms. Finding the answer will require your help, diagnostic testing and possibly time.

Diagnosis starts with a thorough history and physical exam

Figuring out which allergy or combination of allergies is causing your dog’s skin problems and allergic reactions can be challenging for you and your veterinarian. Because itchy skin can be caused by conditions other than allergies, your veterinarian will want to rule out causes such as parasites, bacterial or fungal infections, and systemic diseases.

The process starts with a detailed history, including your dog’s breed, age, gender and reproductive status. When you seek veterinary care for your dog’s skin issue, you can help your veterinarian diagnose the underlying cause by being prepared to provide answers to a number of questions.

  • When did you first notice the clinical signs and symptoms?
  • How did the problem start? How has it changed?
  • How old was your dog when the symptoms started?
  • Where on your dog’s body did you first notice the symptoms?
  • Has your dog had skin or ear conditions before?
  • What treatments or medications have been used before? How did your dog respond to them?
  • Is your dog itchy?
  • Which came first: the changes in skin and hair, or the itching?
  • Does the problem occur year-round, or does it occur only during certain seasons?
  • Are there other pets in the home with similar signs?
  • Are any people in your home having skin problems?
  • How often do you bathe your dog? When was the last bath? What do you use for shampoo or conditioner?
  • Could it possibly be food allergies?
  • What do you use for controlling fleas, ticks or mites? When was it last applied?
  • Is your dog having any other issues (e.g., increased thirst or urination, change in appetite or activity level)?

Your veterinarian will perform a full physical examination, looking for clues as to the cause of your dog’s skin issues. Based on the history and physical exam findings, your veterinarian may request a number of laboratory tests.

These tests may include looking at skin scrapings and hair samples under the microscope and cultures of hair or skin samples to rule out fungal, yeast or bacterial infections. Blood and urine tests may be used to determine if a systemic disease is present. Combing for fleas, skin examination for fleas and flea “dirt” (feces), and skin scrapings for mites and lice also may be performed.

Signs and symptoms of pet allergies

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The most common symptom of dog allergies noticed by dog owners is itchy skin, which dogs relieve by scratching, licking, chewing, scooting and rubbing — to the point of damaging their skin and causing sores, scabs, hair loss and infection. Itchy ears and recurrent ear infections are also commonly seen in dogs with environmental allergies.

If you notice that your dog is scratching more than normal, or has reddened, smelly and sensitive ears, it’s time to schedule an appointment with your veterinarian. Your veterinarian will determine if something other than an allergy is causing your dog’s symptoms (like food allergies), evaluate your pet for any secondary bacterial or yeast infection, and can recommend the most appropriate treatment to help manage your dog’s itchy skin.

Diagnosing flea allergy dermatitis

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Flea allergy dermatitis (FAD) is the most common cause of allergic reaction and pet dander in dogs and a common cause of itching and dog allergies. That’s why veterinarians typically start with diagnostics to determine the presence of fleas and/or flea dirt when investigating skin problems in dogs. Your veterinarian will use the information you provide, such as when signs started, their duration and seasonality, and known or suspected exposure to fleas, in combination with physical exam findings.

During the exam, your veterinarian may or may not find fleas, or may only find flea dirt on your dog’s skin. Intense itching and hair loss in the area from the middle of the back to the base of the tail and down the rear legs is often seen with FAD. Skin damage or open, oozing sores may also be present.

Intradermal allergy tests similar to those performed in people or specialized blood tests can confirm flea allergy in your dog. However, the diagnosis is best confirmed by using strict flea control measures and seeing a positive response to flea control and the dog allergy symptoms.

Diagnosing food allergy

The ideal test to diagnose or rule out food allergy is a strict food elimination diet trial that lasts eight to 10 weeks. Intradermal and serum allergy tests are available to help diagnose food allergies in dogs, but many veterinary nutritionists question the tests’ accuracy.

A detailed diet history is needed so your veterinarian can recommend an appropriate elimination diet, which is a food with either a novel protein and carbohydrate or a hydrolyzed protein. This could be home-cooked or therapeutic dog foods. An elimination diet trial also means no treats, no table food, no rawhides, no flavored chews or toothpaste, and no flavored medications.

If no improvement is seen by the end of the trial — and the trial was strictly performed — food allergy can be ruled out. Your dog can be transitioned back to his or her normal diet and other causes of skin allergies can be followed.

If your dog improves on the elimination diet, the next step is to challenge your dog by feeding the previous food and watching for clinical signs to recur. While this step verifies that the improvement was related to food and not a new medication or shampoo, many owners are often unwilling to try it.

Diagnosing atopic dermatitis

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No specific diagnostic test exists for atopic dermatitis, or environmental allergies. Instead, veterinarians arrive at a diagnosis of atopy by ruling out other causes of itchy skin conditions, the presence of clinical signs and the information in your dog’s history. Among the factors that your veterinarian uses to make a diagnosis are:

  • The dog’s age when the skin condition started
  • The level of itchiness, or pruritus, which is often present before other signs occur
  • The areas on your dog’s body that are affected, such as the feet, face, “armpits,” neck, abdomen and inguinal region
  • Changes in or progression of clinical signs
  • Seasonal or year-round signs and symptoms

After diagnosis, intradermal or serum allergy tests are used to identify the specific environmental allergens so they can be avoided — which is often impractical — or used for therapeutic immunotherapy. Immunotherapy, commonly referred to as “allergy shots,” is designed to improve your dog’s tolerance of specific allergens. Intradermal and serum allergy tests aren’t used to diagnose atopic dermatitis and may not be done unless you’re will to try immunotherapy.

“Seasonal” pet allergies can occur all year long

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The idea that canine allergies are limited to only one season of the year is a myth. Depending on where you live and what your dog is allergic to, your canine companion may suffer during the spring, summer, fall or all year round. Seasonal allergies are also known as environmental allergies, and depending on where you live, environmental allergies like pollen may never fully disperse.

The list of potential environmental allergens is long and includes pollen from trees, grasses and weeds. During spring, tree pollen might be the culprit behind your canine companion’s allergy symptoms. In summer, grass pollen reigns supreme and can contribute to symptoms well into autumn. In fall, weed pollen — especially ragweed, sagebrush and wormwood, depending on where you live — may be the primary cause. And, unfortunately, many dogs are allergic to more than one type of pollen.


Allergy signs can be seen and heard

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Frequent scratching, licking and chewing are easily recognized signs of allergies in dogs. But did you know there’s another common allergy sign that you may be overlooking? Maybe you’re not listening to what your dog’s ears have to say!

Recurring ear problems can be added to the list of signs and symptoms of pet allergies. Dogs are more likely than people to develop intensely itchy skin and red, irritated skin on their feet, belly, head and, yes, ears.


Common and not-so-common causes of environmental allergies in dogs

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Like people, dogs can be sensitive to a long list of indoor and outdoor substances, known as allergens, present in their environment. The most common environmental allergens include pollens from trees, grasses and weeds; molds; dust mites; house dust; certain fabrics such as wool or cotton; chemicals (often associated with fragrances); and tobacco smoke.

Less common causes of environmental allergies include other animals such as the family cat — and even you. That’s right! Just as people can be allergic to dogs (and cats), your canine companion can be allergic to your cat, another family member or you. And although veterinary dermatologists are quick to note that cases of dogs being allergic to cat or human dander are rare, they do test for hypersensitivity to cat dander when performing skin tests.


Here’s how to help your itchy dog during allergy season

The arrival of spring means rain showers, blossoming flowers and greening landscapes. And if you have allergies, you know what else spring brings: allergy season. Just like people, dogs may suffer from environmental allergy symptoms.

Dogs with environmental allergies — also known as atopy or atopic dermatitis — typically have skin problems that result from itching. Excessive scratching anywhere on the body, relentless licking or chewing of the feet, front legs or abdomen, and frequent rubbing of the face, eyes or ears are all signals your pet may be experiencing allergies. These behaviors can lead to skin trauma such as scrapes and scabs, hair loss, abnormal body odor, and bacterial and yeast infections. It’s often this skin damage combined with constant scratching that catches your attention and causes you to question whether something is wrong with your dog. Chronic ear infections can also indicate your dog suffers from environmental allergies. Read on to learn how to spot the signs of allergies and what steps, like allergy testing, you can take to provide some relief to your pet.


Your house could be a home for pet allergens

Pollen from grasses, weeds and trees are a well-known cause of the collar jangles in dogs with allergies. But did you know that your home can be a source of allergens as well? And some of them are so small, you can’t see them.


What’s next

Once your veterinarian has determined the underlying cause of your dog allergy and the ensuing allergic reaction, a treatment plan that’s right for your dog can be formulated. Since allergies can’t be cured, only managed, the goal will be to make your dog more comfortable and control allergy signs and symptoms.

RELATED POST: Allergies: Body Defenses Gone Haywire

The information in this blog has been developed with our veterinarian and is designed to help educate pet parents. If you have questions or concerns about your pet's health or nutrition, please talk with your veterinarian.


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