Allergic Skin Disease in Dogs

Allergic skin disease is one of the most common reasons for veterinary visits in dogs. Some dermatologists estimate that up to 40 percent of the dog population will develop some form of allergic dermatitis during their lifetime. For owners this condition can be very frustrating as there often is no definitive cure, and treatment can be ongoing throughout their pet’s life. So it is important for dog owners to have some knowledge concerning their dog’s skin allergies.

First of all, the three most common forms of skin allergies in dogs are flea allergy dermatitis, food allergy and atopic dermatitis.

With flea allergy the dog becomes sensitized to a protein in flea saliva. The area of the body most affected is the rear half of the dog, especially the rump and down the back legs. Luckily, with the introduction of effective topical and oral flea control medications, we see a lot less of this condition than in the past.

Dogs with food allergy become sensitized to a protein in the diet. This could be chicken, egg, beef, lamb, wheat etc. The most common areas affected are the ears and feet, but over time large areas of the body can become involved. A majority of dogs with food allergy also have some bowel problems. Food allergy is diagnosed by introducing a novel protein diet, or a hydrolyzed diet where the protein is broken down so the body does not recognize it. If the itching resolves then the offending food is fed again to see if itching returns. This is done because a change of season or other factors might be what is responsible for reduced itching. Food allergy is not as common as many people think.

With atopic dermatitis the offending allergens are often airborne and include pollens, molds and house dust mites. As with food allergy, the ears and feet are commonly involved. Other areas of involvement are the face, axilla, groin, and in general hairless areas of the body. Unlike food allergy, symptoms of atopy almost always begin in the first 2 years of life. One way to look at atopy is “hay fever of the skin.” In the beginning most atopic dogs exhibit symptoms seasonally, but may have symptoms to some degree year round; they may be worse in the spring and the fall.  Atopic dermatitis is the most common form of allergic dermatitis we see in dogs.

Whatever the form of allergy, the result is itching. And this leads to biting and scratching, which frequently results in skin infections with bacteria and/or yeast. The skin infection, in turn, makes the itching worse. So we have a vicious cycle of itching, scratching, infection, followed by more itching. Changes of the skin in the ear canal caused by atopic dermatitis and food allergy often result in ear infections. In fact, the most common cause of ear infections in dogs is allergy.

So what can we do?

  1. Since sarcoptic mange (scabies) often mimics both food allergy and atopic dermatitis, in severe cases it is prudent to rule out scabies. This is difficult to do with skin scrapings as the mites are very difficult to find. So often we end up treating with the topical flea medication Revolution, since it will treat this form of mange.
  1. We need to determine if secondary infection is present. If so this needs to be treated by antimicrobials or topical medications or both. Many dogs will need weekly medicated baths to prevent recurrence of infections.
  1. If the itching is year round a food trial is warranted.
  1. Flea control. Dogs with allergic dermatitis of any variety cannot tolerate flea bites, so they should be kept on year round flea control medication. Two excellent flea products are Bravecto, a pill given once every 3 months, and Revolution, a monthly topical spot on treatment. Both of these are unaffected by frequent bathing.
  1. Frequent bathing with a hypoallergenic shampoo. This can help to rinse off airborne allergens and reduce itching. An example of a hypoallergenic shampoo is Vet Solutions Aloe and Oatmeal.
  1. Fatty acid supplementation. Fish oil capsules containing Omega 3 fatty acids can help reduce itching.
  1. Many dogs will also need medication to help control itching. Our choices here is corticosteroids (e.g. prednisone), antihistamines (e.g. hydroxyzine, diphenhydramine), cyclosporin (Atopica), and a new medication Apoquel. Unfortunately, antihistamines are usually not very effective but it can be helpful to give diphenhydramine (Benadryl) at bedtime as it helps with sleep. Probably the most significant advance in medication for allergic skin disease over the past 20 years is the drug Apoquel. We have not seen side effects with this medication, and we can use it either short term or on a long term basis. The problem has been supply as this drug is difficult to manufacture and the demand has been very high. The supply is getting better and we are now placing new patients on this medication.
  1. Immunotherapy for atopic dermatitis. In severe cases, allergy testing by either skin tests or blood tests can be performed; the goal is to develop a vaccine to desensitize the dog. The vaccine can be given by injection or an oral formulation. This can be very helpful but is a long term treatment and results may take some time. Expect more on this in a future blog posting.

Carl D. Anderson DVM

Canine Influenza “Dog Flu”

Many clients have inquired recently about a new dog influenza virus (H3N2), and the possibility of an outbreak in our area. This illness is suspected in a dog in Kent but the investigation is still ongoing. Here are some thoughts we have regarding this development.

Canine influenza (H3N2) is a respiratory disease that can cause sneezing, coughing, runny eyes, runny nose, and in severe cases fever and lethargy in dogs.  The symptoms are very similar to “kennel cough”, which is a general term for contagious respiratory disease in dogs caused by several organisms including bacteria and viruses. One difference with canine influenza is that symptoms may last several weeks. Nonetheless, with proper supportive care most dogs with canine influenza will fully recover. The mortality rate of this disease is quite low. But since H3N2 is a new virus our dogs have no natural protection. This fact combined with the mode of transmission makes H3N2 highly contagious. Infected dogs may be contagious for several days prior to showing any clinical signs. The population of dogs that are in the highest risk group are those that frequent high density areas such as dog parks, doggie daycare, dog shows, or grooming facilities.

The best way to protect your dog is through vaccinating and/or avoiding potential exposure.  A vaccine for H3N2 is available that aids in the control and prevention of disease caused by this virus. The vaccine can be given to healthy dogs 8 weeks of age or older; initially administered as two doses given 3 weeks apart and then as a yearly booster.

The H3N2 vaccine is not recommended for every dog. Unlike canine distemper, parvovirus enteritis or rabies, canine influenza is generally a mild disease with a very low mortality rate.  This fact, along with lifestyle considerations which affect your dog’s risk, must be factored into your decision of whether or not to vaccinate. We encourage our clients to do their own research and feel free to discuss this decision with a veterinarian at our office. We do currently have a vaccine available in stock.

Sincerely,

Carl Anderson DVM

Eastlake Veterinary Hospital

For more information, please refer to this recent article published by WSU:

Canine Influenza confirmed as H3N2

 

Clinic Refresh!

View of the New ClinicIn celebration of our 30 year anniversary, we recently completed a clinic refresh which includes all new LED lighting, artwork, interior paint, cabinet work, and other alterations to give our clinic interior a new modern appearance. If you are in the neighborhood we would love for you to drop by to see our new design and, if interested, have a cup of coffee.

Exciting New Flea and Tick Product

We are excited to now offer Bravecto to our clients as another alternative for flea and tick control in dogs. Bravecto is an oral product introduced by Merck Animal Health that is administered as a highly palatable chewable treat. What is especially nice about this product is that it is effective for twelve weeks with a single dose, kills fleas and ticks rapidly, and being an FDA product has undergone extensive safety testing. In fact, Bravecto is even safe for pregnant and lactating female dogs.  And because Bravecto is a systemic product, its efficacy is not affected by bathing or swimming or grooming.