Allergy, Intolerance and Itchy Dogs

Our dogs have a “simple” digestive system compared to other domesticated animal. For this reason it is unsurprising that so many are intolerant to certain food ingredients. We know how common lactose intolerance is in humans, right? This is because many of us do not produce the enzymes needed to digest lactose in milk. Dogs can also have problems to digest particular food ingredients.

Food intolerance is not to be confused with hypersensitivity (that’s allergies to you and me). Food allergies are erratic immune response within the animal. With dogs, these responses are often seen in the digestive tract and skin(1). In humans we often see wheat allergies, where sufferers react to a protein in wheat. Food allergies in dogs are almost exclusively caused by certain proteins (2).

Common symptoms of food intolerance vs. allergy in humans

Allergic reaction in dogs

In dogs we diagnose intolerance or allergy from what we observe, sometimes followed up by allergy tests. As an owner, we can often identify what is causing a reaction though eliminating common allergens. If you are concerned about allergies, do not hesitate to take a trip to the vet!

When our dogs are allergic to a dietary protein, we often see skin reactions including atopic-like dermatitis (ALD)(7,8). This can be very uncomfortable for the animal. Colitis and diarrhoea could be signs of allergy in dogs, but could also be signs of intolerance(1,9).

Soy is often added as an inexpensive protein source in commercial dog foods. A recent study identified soy as the cause of ALD in 21/49 dogs investigated with an activated immune response(8).

Storage mites

Storage mites are microscopic bugs found in commercially prepared foods. Dry dog food provides the ideal conditions for mites to reproduce and proliferate. A survey identified storage mites in 9/10 bags of dog food examined(10). Gross, right?

Common storage mites (including Acarus siro, Blomia tropicalis, and Tyrophagus putrescentiae) can cause allergic reaction in the form of ALD in dogs(11). Reactions can be seen in both healthy dogs and those previously affected with ALD(12).

Long-term impacts and solutions

Although intolerance is unpleasant and will affect quality of life in the long-run, it will not immediately harm the animal. Allergies on the other-hand can be more severe. Even low-level chronic inflammation can irreversibly impact health overtime(13). So it is important that intolerances and allergies are identified and managed.

There are some ‘hypoallergenic’ commercial dogs foods out there, which seem to be affective at reducing allergic reaction in some cases(14,15). These diets contain broken down proteins, called protein hydrosylases. If you’ve ever had a protein shake, you’ve probably consumed protein hydrosylases. Sometimes homemade diets are recommended, providing that they are correctly formulated(16).

The take-home message

All dogs are at risk of intolerance and allergies to ingredients in their food. It’s really important that you keep an eye out for symptoms such as dermatitis, diarrohea and colitis. If intolerances or allergies are left unmanaged overtime, they will effect the health and welfare of your dog. Allergic reactions are more severe than intolerances. Allergy may be caused by the protein source that you’re feeding, or even storage mites present in dry food. Changing your pet food may be all it takes to resolve the issue, but if you are concerned then ask a vet!

Be aware: it is not unheard for dogs to be allergic to several proteins at once.

M. A. Crisci

References

1. Paterson, S., 1995. Food hypersensitivity in 20 dogs with skin and gastrointestinal signs. Journal of Small Animal Practice, 36(12), pp.529–534.
2. Verlinden, A., Hesta, M., Millet, S. and Janssens, G.P.J., 2006. Food allergy in dogs and cats: a review. Critical reviews in food science and nutrition, 46(3), pp.259–273.
3. Nhs.uk. 2016. Food allergy — NHS Choices. [online] Available at: http://www.nhs.uk/conditions/food-allergy/Pages/Intro1.aspx [Accessed 20 Sep. 2017].
4. Nhs.uk. 2016. Food intolerance — NHS Choices. [online] Available at: http://www.nhs.uk/Conditions/food-intolerance/Pages/Introduction.aspx [Accessed 20 Sep. 2017].
5. Jeffers, J.G., Meyer, E.K. and Sosis, E.J., 1996. Responses of dogs with food allergies to single-ingredient dietary provocation. Journal of the American Veterinary Medical Association, 209(3), pp.608–611.
6. Raditic, D.M., Remillard, R.L. and Tater, K.C., 2011. ELISA testing for common food antigens in four dry dog foods used in dietary elimination trials. Journal of animal physiology and animal nutrition, 95(1), pp.90–97.
7. Chesney, C.J., 2002. Food sensitivity in the dog: a quantitative study. Journal of Small Animal Practice, 43(5), pp.203–207.
8. Suto, A., Suto, Y., Onohara, N., Tomizawa, Y., Yamamoto-Sugawara, Y., Okayama, T. and Masuda, K., 2015. Food allergens inducing a lymphocyte-mediated immunological reaction in canine atopic-like dermatitis. Journal of Veterinary Medical Science, 77(2), pp.251–254.
9. Nelson, R.W., Stookey, L.J. and Kazacos, E., 1988. Nutritional management of idiopathic chronic colitis in the dog. Journal of Veterinary Internal Medicine, 2(3), pp.133–137.
10. Brazis, P., Serra, M., Sellés, A., Dethioux, F., Biourge, V. and Puigdemont, A., 2008. Evaluation of storage mite contamination of commercial dry dog food. Veterinary dermatology, 19(4), pp.209–214.
11. Arlian, L.G., Schumann, R.J., Morgan, M.S. and Glass, R.L., 2003. Serum immunoglobulin E against storage mite allergens in dogs with atopic dermatitis.
12. Mueller, R.S., Fieseler, K.V., Rosuchuk, R.A. and Greenwalt, T., 2005. Intradermal testing with the storage mite Tyrophagus putrescentiae in normal dogs and dogs with atopic dermatitis in Colorado. Veterinary dermatology, 16(1), pp.27–31.
13. German, A.J., Hall, E.J. and Day, M.J., 2003. Chronic intestinal inflammation and intestinal disease in dogs. Journal of veterinary internal medicine, 17(1), pp.8–20.
14. Loeffler, A., Lloyd, D.H., Bond, R., Kim, J.Y. and Pfeiffer, D.U., 2004. Dietary trials with a commercial chicken hydrolysate diet in 63 pruritic dogs. Veterinary Record, 154(17), pp.519–521.
15. Olivry, T. and Bizikova, P., 2010. A systematic review of the evidence of reduced allergenicity and clinical benefit of food hydrolysates in dogs with cutaneous adverse food reactions. Veterinary dermatology, 21(1), pp.32–41.
16. Roudebush, P. and Cowell, C.S., 1992. Results of a hypoallergenic diet survey of veterinarians in North America with a nutritional evaluation of homemade diet prescriptions. Veterinary Dermatology, 3(1), pp.23–28.