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This may have been the worst cliff-hanger in the history of blogging, but this article – Part 2 of The Itchy and Scratchy Show – will continue our discussion on why dogs may exhibit allergies. Last article we looked at fleas and flea bite allergies; today we will discuss food allergies and atopy, or atopic dermatitis.
Food Allergies
Food allergies are, in short, a hypersensitivity reaction caused by an immune system reaction to a specific protein in the diet. They are not as common as we may think and they are less prevalent than environmental allergies.
Generally, when we see a dog in clinic with suspected food allergies they present with generalised pruritus (itchiness), which can vary in location from patient to patient. Reactions can occur around the face, ears, and ventrum (belly), which mimic environmental allergies, or dorsum (back), tail base, and back legs, which are areas commonly seen with flea allergies, and can even affect the front legs, paws, around the eyes, armpit areas, etc.
Food allergies are non-seasonal, meaning as long as the dog (or cat) is fed the offending protein, it will cause the allergic response; compared with environmental allergies, which are largely seasonal.
Diagnosing a food allergy can be quite difficult, as there are no reliable diagnostic tests to confirm a food allergy. On the other hand, intradermal (skin) and even blood test can be used to detect other allergies. Unfortunately, these are not as reliable when it comes to food allergies.
Couple this with the fact food allergies can appear at any age between 2 months old to 14 years old and it is easy to see why this may complicate diagnosis. Adult onset food allergies can occur when a certain protein is fed for over 2 years as well, so even though “my dog has been eating the same thing for a very long time”, they can still develop allergies to something in the food.
The most common allergies in dogs include chicken, beef, eggs, corn, milk, soy, and wheat, although any protein can be the cause of allergies.
The only way to properly diagnose a food allergy, and I use the term diagnose lightly here, is with a strict food elimination diet. This means feeding a special diet with either a novel protein (kangaroo, venison, horse for example) or with a diet composed of hydrolysed proteins, meaning proteins that are chemically “cut” into smaller protein chains that are not large enough to trigger the body’s immune system. These are available as commercially prepared diets at veterinary clinics or can even be home-cooked. (Please speak to your vet if home-cooking is something you may be interested in to ensure a complete balanced diet). New diets must be fed for a minimum of 3 months to see if there is any change to the degree of pruritus. Trust me, food trials are frustrating. Not only do they last 3 months, but during this time NO other foods can be given, even some flavoured medications are off-limits during this time; and as I mentioned before, they do not diagnose WHAT the patient is actually allergic to, but can only help confirm the presence of a food allergy. During these months, the vet may start treatment with glucocorticoids or other “allergy medications” to relieve symptoms until the food trial has enough time to show effects. If after 3 months the pruritus is resolved, we can confirm the presence of a food allergy.
Another step that can be taken is to slowly re-introduce foods that are the potential cause of the allergy, and see if the patient restarts the allergic signs. I wont get into the details of the re-introduction trial, but from experience, when a food is finally found to reduce allergy symptoms, clients generally are not interested in finding what the initial cause was, and will remain on the special diet indefinitely.
Atopy
Atopy, or Atopic dermatitis, is the general term we use to signify an allergic response to things in the environment. This does include seasonal allergies (pollen, trees, grass, etc.) but can also include household items (detergents, cleaners) or even human skin. Yes, it happens, cats and dogs can be allergic to us!
Generally, atopy develops sometime between 6 months and 3 years of age. It generally occurs seasonally (spring and early autumn being the most common times), however they can also be year-round.
Diagnostic tests are available for atopic pets. These include intradermal testing (which are available through specialist dermatologists) or blood tests that are available through general practice vets that measure the immune response or exposure to certain allergens. In fact, if offending allergens are found using any of these methods, there is a possibility of developing specific “vaccines” (as injections or oral tablets), which help to reduce the immune system’s response to the allergens. These vaccines may have to be given for the lifetime of the patient as well, and require at least 1 year or treatment to see if there is any positive response.
What we sometimes fail to convey to clients with atopic pets is that there is NO cure for these allergies. There are precautions we can take, and vaccines, medications or special shampoos we can prescribe to limit the symptoms but nothing will completely cure the allergy itself. The patient may not exhibit allergic tendencies anymore, but they will remain allergic throughout their lives.
This is only a short overview of allergies in pets. As you can imagine, textbooks have been written on this complicated subject. If you need more information on allergies or if you believe your pet may have allergies, please talk to your vet.
If you have any questions, queries, comments, or just feel like telling me how great this column was, you can send any or all of the above to: AskDrJames@outlook.com. All questions used for blogging purposes will remain 100% anonymous.
