February 2013

Pet Section: Does Your Dog or Cat Have the "Mange"?

Author: Kirk Dixon

I’m sure you’ve seen it—the miserable dog or cat that is half bald, has lizard-like skin and is all covered in scabs. The poor thing is so itchy it can’t stop tearing itself apart between biting, chewing, and/or scratching. When I first came here over 27 years ago, that animal was often presented with the added history that the owner had tried everything, even “burnt” motor oil.

Now these animals didn’t have Sarcoptic or Demodectic mange, which are real infections by microscopic parasites called mites. They had “the mange,” that obnoxious, pesky skin disease that seemed to require so many home remedies before they ever saw a veterinarian.

While the diagnosis made by the general public has changed a lot, the problem deemed as “the mange” has not. The most common problem that I have seen since my arrival in 1985 is skin allergies.

To start, let’s discuss the difference between people and pets. Defense cells in our bodies are constantly patrolling, looking for invaders to attack and destroy. When they see an invader, they attach themselves to it and call on their buddies to come help wipe out the intruders. It is a wonderful system, as it keeps us safe from many bacteria and viruses. However, some of these patrolling cells inappropriately identify harmless pollens as life threatening attackers. They attach themselves to the pollen and start releasing chemicals, including histamines, which cause all kinds of inflammation.

With regard to inhaled pollens in people, the cells that release the chemicals are in the highest concentration in our respiratory tract. So if we breathe in something we are allergic to, we get hay fever or asthma. However, in dogs and cats, those cells are almost nonexistent in the respiratory tract. Instead, they are highly concentrated in their skin, especially face, feet, armpits and groin. Hence their primary symptom is scratching, and they will usually scratch the most in one or more of those areas. A few cats will get asthma, but it is virtually nonexistent in dogs.

Another version is a food allergy. In people, food allergies can cause respiratory inflammation in the form of anaphylaxis, skin problems and intestinal problems. In dogs and cats, GI and respiratory problems are rare; instead, the usual symptom is, once again, scratching. Nationwide, the statistics for pet allergies are 90 percent inhalant, 10 percent food. A common misunderstanding regarding food allergies is to what exactly they are allergic. Many people think that the latest dietary fad, which is a grain-free diet, is hypoallergenic. The pets are not allergic to a brand, and an expensive, high-quality food is not less likely to cause allergies than a cheap food.

They are sensitive to ingredients, of which the protein source is the most likely offender. So that expensive grain-free diet is just as likely to be a problem as it is loaded with even more beef, chicken, lamb, etc.

Before we proceed, I’m sure you want to know why animals become allergic. The answer is no one knows why. What we do know is that allergies are acquired. You have to be exposed to the allergen and develop the sensitivity; then when you are re-exposed, you will show symptoms. When it is understood how to switch off an allergy, it will also be understood how to cure autoimmune diseases and probably cancer. Hence, we can’t cure an allergy; we can only treat the symptoms or, in the case of foods, avoid the allergen.

So how do we treat allergies? First, you could avoid the allergen. That is the method of choice with food allergies but virtually impossible with inhalant allergies. Pollens can blow for over two miles, so what the pets are allergic to doesn’t have to be in your own neighborhood. In addition, you would have to go hundreds of miles to get somewhere that had different allergens. I have many clients who live part of the year up north and part here. A common story is that the dog is fine up north, but literally starts scratching by the time they reach the bridge to the island.

Because of our temperate climate and high humidity, the environment is green year-round, which also means we have pollens year-round. In addition, we typically have more than 10 times the pollen counts of an arid climate like Arizona.

In people, antihistamines can often work very well. However, in dogs, they are usually beneficial if the animal is only slightly itchy. If they are real itchy, antihistamines are about as effective as “spitting into the wind.” Shampoos, fatty acid supplements, and leave-on conditioners all can help somewhat, but they are best used as adjuncts to therapy, not as the primary means of therapy. Allergy testing and subsequent desensitization with shots of the allergen used to be more popular, but, it is very expensive and more often than not either doesn’t work or only helps a little.

Cyclosporine is a drug that was developed as an immune suppressant to help keep transplant recipients from rejecting their new organs. It is safe to use, with few side effects, but it is very expensive and often requires other things to help it work adequately. That leaves corticosteroids, (prednisone, triamcinolone, methylprednisolone, etc.) which are the old standby. Depending on who you ask, they can either be the greatest drug ever developed or a horrible scourge that is overused.

While they can cause health problems, I find the problems are rare compared to their effectiveness. The problem is with over-usage, and for me, using pills very often leads to overuse and problems. I use an injectable trick I learned from an “old timer” before I became one, and with a little prudence and regular monitoring, the problems are few and far between. You will want to consult your veterinarian for the best approach for you.

This leaves food allergy testing and treatment. There is a food allergy blood test, but most dermatology experts agree it is horribly inaccurate. I use the response to cortisone for my screening. Inhalant and flea allergies are very responsive to cortisone. Food allergies are not. So if I give two back-to-back injections that appear to be worthless, that is my cue to try a food trial. Without a doubt, a food trial is the best diagnostic method. There are two ways. First is to use a limited antigen diet that has ingredients that your pet has never had before (remember allergies are acquired and they have to have previous exposure to be allergic). Examples are foods with kangaroo and oats, venison and potato, duck and potato, etc.

The downside is that these diets are more likely to cause diarrhea in some animals. The other option is a hydrolyzed diet—that is where the molecules of the food are broken down too small for the body to recognize it. So while it may have chicken in it, the body only sees a generic protein. That type of diet has been the most effective for me. If you are doing a food trial, you must understand it will take up to eight weeks for 85 percent of the allergic dogs to respond. That means no treats, just the food and water only, or it will be a waste of time and money.

One last thing is that fleas and hormone problems like low thyroid can greatly agitate allergies and decrease the effectiveness of treatment. Flea control is a must here, and every dog and cat should be on a regular flea treatment regimen. So consult your veterinarian if you have an itchy pet so it doesn’t end up looking like an animal that has “the mange.”

Kirk Dixon, DVM practices veterinary medicine at Hilton Head Veterinary Clinics, with locations on Hilton Head Island and in Okatie. For more information visit hiltonheadpet.com or call (843) 681-2890 for Hilton Head or (843) 705-9959 for Okatie.

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