Canine Atopic Dermatitis (Atopy)

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Clarissa Owens
5 years ago
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1 Canine Atopic Dermatitis (Atopy) What is atopic dermatitis? Atopic dermatitis (atopy) is an inherited predisposition to develop allergic symptoms after repeated exposure to some otherwise harmless substance. These trigger substances, (called allergens ) can be anything the dog comes into contact with, eats or inhales - such as dust, dust mites, grasses, or pollen. Most dogs begin to show their allergic signs between 1 and 3 years of age. A few dogs may show clinical symptoms as early as 6 months of age. It is also unusual to see clinical symptoms start after 7 years of age. Because of the hereditary nature of the disease, several breeds (including Golden Retrievers, Labrador retrievers, most Terriers, Irish and English Setters, Lhasa Apsos, Dalmatians, Bulldogs, Beagles, Miniature Schnauzers, Pugs, Boxers, Cocker Spaniels, and Shar Peis) are more commonly atopic. What causes atopy? Atopy is essentially a disease of the immune system. Normally the body s immune system has a controlled and moderate response to a foreign substance (called an allergen). This is usually very mild and shouldn t cause any issues. However in some individuals, the immune system has a large overreaction to one or more allergens (called a hypersensitivity reaction). This reaction causes excessive release of inflammatory chemicals such as histamine, as well as recruiting further inflammatory cells into the mix. These chemicals and the accumulation of inflammatory cells cause the skin to become inflamed and this then results in itching/redness. Here begins the vicious cycle of allergy. The inflammation then causes skin damage and the natural defense of the skin is breached. This then allows secondary pathogens to take hold which causes further inflammation etc and thus the cycle spirals again. Hayfever in humans is a good example of a hypersensitivity reaction. The pollen causes an excessive response of the immune system which causes release of histamine. This causes redness of the eyes, nose. If you then rub your eyes, the redness and soreness gets worse etc. As long as there is pollen around, then hayfever sufferers will continue to suffer, unless treatment is undertaken. Page 1 of 5

2 What are the symptoms of atopic dermatitis? Many different types of skin disease can often have very similar symptoms. Therefore it is very important for your vet to try and rule out simple and obvious diseases first. For example if your pet starts scratching, it could just be fleas! The symptoms of atopic dermatitis can include the following: Generalized itching Scratching Chewing/Biting/Licking Thinning of the hair or hairloss Redness of the skin/eyes/muzzle Scaling/Crusting of the skin These signs are often manifested as: Licking of the feet/toes Redness in armpits/groin/tummy Red Ear flaps or ear infections Change in coat or excessive dandruff. Thickening or darkening of the skin You may also notice the following which are often due to secondary infections: Yeasty smell about the dog Greasy feel to the coat Spots or pustules on the skin Smelly sore ears Smelly paws How is the diagnosis made? Diagnosis of atopic dermatitis is usually based on clinical signs (areas of itching) and often, an initial seasonality to the skin problem. However, some dogs will have no seasonality to their itching from the onset of their symptoms. In addition, many seasonally allergic dogs soon begin to scratch and rub year round. It is also a diagnosis of exclusion i.e. it will be necessary to rule out other causes of skin diseases by performing a variety of simple tests. These may include: Tape strips to check for yeasts/surface parasites Skin scrapes to check for burrowing parasites Possibly skin biopsies to check for any underlying disease process. Blood tests to check for underlying metabolic or hormonal illnesses Blood tests to check levels of particular antibodies to known allergens Intradermal skin tests ( prick-tests ) to measure allergic response to known allergens. Page 2 of 5

3 What treatment is available? Treatment falls into three broad categories: Drugs to remove the itching sensation and reduce inflammation. Also the use of antibiotics, anti-parasitic or anti yeast treatments to control any secondary disease. Identifying and subsequent avoidance of exposure to allergens Use of vaccines to desensitize the animal and reduce the inflammatory response. DRUGS 1. Antihistamines and fatty acids are two therapies, when given in combination that can decrease the itching sensation in about 10% to 20% of atopic pets. Your pet can be on antihistamines and fatty acids for life with no long-term problems. The only side effect sometimes seen with antihistamines is drowsiness. Several different types of antihistamines may need to be tried to find the one that works the best. These two combined therapies should be given for a few months before a decision is made concerning their effectiveness. In realistic terms, anti-histamine usage is often disappointing and only seems to be effective in a few animals, and often these are only those animals with mild signs. 2. Corticosteroids (prednisolone, cortisone) can also be used to alleviate the itch. These drugs are excellent at controlling the clinical symptoms, however, they do have potential side effects and are ideally reserved for pets for where other therapy is not possible, therapy is ineffective or to control a severe itch for a short period of time. 3. Cyclosporin is a relatively new drug which is often highly effective at controlling the symptoms of atopy. It works, like steroids, by reducing the inflammatory response of the skin. The drug is generally safer for long term use than steroids, but is currently very expensive which often makes it use prohibitive. There are also certain drugs (some antibiotics and vaccines) that shouldn t be used at the same time as using this drug. 4. Malaseb Shampoo is a special shampoo that helps reduce the amount of secondary yeast infection (Malassezia) in the skin. This shampoo needs to be used regularly and it is very important to leave it on the skin for at least 5 minutes for it to be effective. 5. Antibiotics often have to be given for quite prolonged periods of time with skin disease. It is not uncommon for animals to have to under several weeks of sustained treatment. Also it may be necessary to repeat treatments if skin infection flares back up again. 6. Antiparasitic treatments. These are usually flea or mange treatments and are vital in both treating existing parasitic infections, but also preventing complicating existing atopic disease with a new infection. Page 3 of 5

4 AVOIDANCE Avoidance can be difficult as you may not be able to easily identify the trigger allergens that your pet may be allergic to. However it is known that certain common allergens frequently have a role to play, and although complete avoidance of the allergic substance may not be practical, decreased exposure may be feasible. Page 4 of 5

5 POLLEN: Decreasing the outdoor exposure especially at dusk and dawn is helpful. Your pet should never be walked through fields with high grass or weeds and should not be outside when the lawn is cut. FUNGI/MOLD: You pet should not be kept in rooms with high moisture levels (bathroom or laundry room) or allowed to be in areas of increased dust. HOUSE DUST MITES: Avoidance may be a major undertaking, involving the removal of carpeting, covering mattresses, regular washing of the bedding, high-efficiency vacuuming, avoiding stuffed toys, and frequent damp mopping of the areas most frequented by your pet. FOOD ALLERGENS: certain food types are more likely to cause skin disease than others. For example, beef proteins, wheat, and gluten are often culprits. Certain foods are known to be free of these and our vets will be happy to advise you on different foods to try your pet on. Food allergies are usually diagnosed by process of elimination and results of food trials with a variety of different foods. DESENSITIZATION VACCINES Desensitization vaccines can be formulated for your pet on the basis of results of a skin test or blood test. After an initial series of injections, periodic boosters are needed (every few weeks) for the remainder of your pets life. 60% to 80% of animals improve with such vaccines. However, desensitization takes time. Improvement may not be seen for 3 to 6 months or longer. If results are not seen within 9 to 12 months, a reevaluation of the vaccine usage is necessary. In reality it is felt that there is quite a varied response to the vaccines. Some dogs seem to do very well, whereas others don t seem to respond at all. There have also been some reported side effects with the vaccines, including worsening of signs and, very rarely, some anaphylactic reactions. However it is a useful option to have, and can result in good control with no drug intervention. Conclusion One of the keys to bear in mind with animals with atopy is that you rarely achieve CURE, but realistically you are aiming to obtain CONTROL. It is important to realise that by concentrating on treating the secondary problems (skin infections, ear infections etc) you will find yourself in a peak and trough situation where the problems will keep on recurring. With any kind of allergic disease, it is so important to try and tackle the problem at the root ie the allergens themselves and the primary inflammation. However It is highly likely that some form of long term treatment is going to be required. Time, patience and working with the vet is the key! Page 5 of 5

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