How to Recognize and Treat Canine Skin Allergy

Overview: Skin Allergies

The three most common causes of canine skin allergy are dog flea allergies, an environmental allergy such as pollen or mold (called canine atopy), and dog food allergy. Any investigation should start with eliminating these common causes before moving on to other possible reasons for a canine skin condition.

Where your dog has an allergic reaction can be a clue as to the cause. If the allergy is at the mouth and you had just purchased a new plastic dog dish for example, this could be the cause. Redness around a flea collar could be caused by the collar itself.

Many chemicals can cause your dog to have an allergic reaction. This usually occurs in areas that are not covered by hair. Common causes include soap, shampoo, wool, leather, plastic/rubber dog dishes, insecticide, paint, carpet, wood preservative, neomycin (many skin medicines).

Canine Skin Allergy Due to Fleas
(Flea Bite Hypersensitivity)

Dog flea allergies are the most common type of canine skin allergy. This condition is confusing for dog owners  since it is a year round problem that many owners believe is seasonal.  To be clear, the problem is worse during the late summer and fall. 

Fleas do not die in the winter and may not be seen by the owner on the dog (they are good at hiding).  A small number of fleas can result in a flea allergy skin problem.

Canine Flea Allergy Skin Symptoms

Symptoms of canine skin allergy from fleas includes itch primarily above the tail base and on the back of the thighs, but can effect the entire body. Dogs will chew on the itchy areas, causing hair loss, red skin and skin irritation. The chewing can also introduce bacteria, which will result in a skin infection. Flea bite hypersensitivity does not typically affect a dogs face or the front of the body.

Canine Flea Allergy Treatment

To treat dog flea allergy, first use a product to kill the fleas on the dog such as a herbal flea dip. Follow this by a product made for dog flea protection recommended by your veterinarian such as Frontline.

Canine Atopy - (Canine atopic dermatitis)

Environmental Dog Skin Allergy and Dogs with Seasonal Allergies

About 1 in 10 dogs get some type of canine skin allergy (also called Atopy) from substances in the air. Allergies tend to appear during certain times of the year when specific types of allergens such as pollen, ragweed and mold are present.

Canine Skin Allergies From Food

Canine food allergy is the third most common type of allergies in dogs. The allergic reaction is to a protein found in commercial dog food, dog treats or table scraps given to the dog. A dog can become allergic to a food at any time, even if a dog has been eating that food for years with no issues.

Allergy Dog Testing and Diagnosis

Diagnosing dog skin allergies often requires the investigative skills of Sherlock Holmes. Any examination will start with the taking of a thorough medical history regarding your dog's symptoms. Some veterinarian's will ask you to complete an online dog skin history that can be filled out before your visit. Typical questions include when the symptoms first began, whether any siblings have similar dog skin problems, and how has the skin reaction changed over time. They will also ask about any products used to care for your dog such as flea care and the diet. Often the questionnaire is more important that the physical exam, since symptoms are often non-specific to any particular underlying cause.

Next, the veterinarian will do a physical exam. A vet will evaluate the entire dog, not just the area showing canine skin allergy symptoms. At this point, for most dog skin disorders, a vet will have some indication or suspicion of what is causing the problem, including dog flea allergy, atopy (environmental allergies), contact allergy (to a chemical or other substance), or if the cause is unrelated to allergy (see below).

Since it is sometimes difficult to tell the difference between skin allergies caused by fleas and allergy caused by something in your dog’s environment, your vet may take an ear swab and a superficial dog skin sample to determine if the problem is caused by an infection (bacterial) or yeast. All are examined using a microscope.

In an approach that is similar to the one used for people, your Veterinarian may give your dog a skin test (IST) where different causes of allergy are placed on the skin. If your dog reacts to a small amount, it means they are allergic. Some Veterinarians may opt to do a blood test called ELISA.

Dog Skin Problems with Symptoms that are Similar to Canine Skin Allergy

Several types of canine skin conditions are often confused with canine skin allergy. When reaching a specific diagnosis, the veterinarian will eliminate these causes before determining that allergy is the cause of the dog skin condition.

• Mange: There are two different types of dog mange, demodectic and sarcoptic, that can mimic the signs of canine skin allergy. Both are caused by mites which burrow under the skin and are treated with a lime-sulfur dip such as Naturasil.
  
  -- Demodectic Dog Mange is commonly seen in young puppies, larger breed dogs such as Great Danes and other breeds such as Boxers, and Pit Bulls. Symptoms includes patchy hair loss around the head and face, but can occur  in any area of the body. Diagnosis is based on a skin scraping and the discovery of mites.
  
  -- Sarcoptic Dog Mange or Scabies is also caused by mites and can be passed between people and dogs. Symptoms usually appear at the ear margins, will appear crusty and in most cases cause extreme itch. A dog scabies diagnosis is based on a skin scraping.
   
• Dog Ringworm results in symptoms such as skin crusting, patchy hair loss and itch. The symptoms usually do not look similar to the circular ring seen on human skin. Dog ringworm diagnosis is based on a test using a "woods lamp" which causes the fungus to fluoresce. Treatment involves the weekly use of a dip such as Naturasil for Ringworm.
  
  
• Immune Mediated Dog Skin Disease can affect dogs of any age, but is most frequently diagnosed in middle age females. In these types of conditions, the dogs immune system attacks its' own body, causing conditions such as pemphigus foliaceus or lupus. Symptoms includes raw dog skin and painful skin at the margins of the ears, dog lips and nose. The condition is diagnosed with a skin biopsy test.

Treatment of Dogs with a Canine Skin Allergy

Many Vets will prescribe an antihistamine (hydrocortisone or Pramoxine) to help with any dog skin itching. Popular types of antihistamine include Dipehnhydramine (Benadryl), hydroxyzine (Atarax), clemastine (Tavist) and cetirizine (Zyrtec); 40% of dogs respond to this type of treatment.

Other treatment options includes oral or topical antibiotics and anti-fungals. Shampoos and sprays may also be of help. If dog food allergy is the cause, then a hypoallergenic food trial is used to identify the problem ingredients. For seasonal allergy (canine atopy), then medication which are immune modulating such as cyclosporine are prescribed.

If your dog does not respond to  any of the canine skin allergy treatments suggested above, then a series of allergy shots can be used to reduce sensitivity to the allergens (called hyposensitization therapy). This course of treatment takes as few as 9 and as many as 12 months.

During recovery, dietary supplements might help to restore skin condition, such as the omega fatty acids found in fish oil. Shampoos can also be tried to ease skin inflammation and itch such as a product that contains colloidal oatmeal (Groomers Blend). Homeopathics that combine ingredients associated with skin and coat health such as Skin and Coat Tonic may also be of help.

It is common for a vet to request a return visit after several weeks to check on your dog's progress.

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References for Skin Allergies on Dogs

Brevitz, Betsy DVM, Hound Health Handbook; "Allergies, Itching and Other Skin Allergies"

Greek, Jean, DVM, ACIDM;  New Hope Animal Hospital  “Atopic Disease and Allergy”

Beale, Karin M. DVM, Gulf Coast Veterinary Specialists – “Atopic Dermatitis: Clinical Signs and Diagnosis”

Giffin, James M. MD & Carlson, Liisa D., DVM “Dog Owner’s Home Veterinary Handbook”.

Lloyd, Professor David, Royal Veterinary College, Hawkshead Campus: “Diagnosis & Management of Adverse Food Reactions in Dogs”

Osborn, Sarah Colombini DVM, Southwest Veterinary College, Houston: “Optimal use of Hypoallergenic Diets”

Ihrke, VMD, Professor of Dermatology, School of Veterinary Medicine, University of California: “Flea Allergy Dermatitis”