When pets display dermatological and gastrointestinal symptoms, pet owners are often immediately suspicious of a food allergy but unfortunately it isn’t that simple. While food allergies (Adverse Food Reactions aka AFR) are a recognised clinical condition in dogs and cats, however the condition isn’t as well understood as in humans.
While AFR can occur, environmental factors are more common triggers for these symptoms in dogs and cats (particularly dermatological symptoms or atopy) but it doesn’t mean it isn’t important to talk about food allergies. AFR can and do happen, and their management and diagnosis is involved and often a long process.
Some statistics
First, let’s get some background figures. When we talk about allergies, approximately 90% are triggered by environmental allergens (pollen, dust, fleas, etc) where 10% is related to food.
Of that 10%, the most common food allergens vary based on geographical location but are primarily animal proteins; In a dog living in Australia, Europe or North America, the allergens most likely contributing to AFRs are beef, dairy, chicken, wheat and lamb. In cats, the most common allergens causing AFRs are beef, fish and chicken. However, we can’t be sure of the true prevalence of certain allergies as not all pets undergoing a diagnostic food trial actually challenge all different protein sources – but more on that later.
Food allergies have no age or sex predisposition, however 22% of dogs will show signs of food allergies (dermatological or gastrointestinal) by 6 months of age and 38% by 12 months of age. In the case of affected cats almost half develop symptoms before two years of age, with first symptoms appearing anywhere between 6 and 12 months.
German Shepherds, Labrador Retrievers, French bulldogs, and West Highland White Terriers appear to be over-represented. There is no clear breed predisposition in cats, however Siamese do appear to also have a higher prevalence. However, any breed or mixed breed can develop a food allergy.
Between 25-49% of allergic dogs will have a food allergy, and their overall reactivity was shown to be reduced when fed a hydrolysed elimination diet.
Diagnosis
To determine if your pet has a food or environmental allergy, you need to conduct a lengthy and strict food elimination trial with a diet that has been clinically validated for this purpose. The most common food protein allergens range from 15-40kDa in size, meaning the body can recognise them and launch an attack – so feeding a hydrolysed diet with all proteins broken to be smaller than this is necessary to truly eliminate the presence of any allergens. This is why a veterinary hydrolysed diet is typically used for the first 6-8 week elimination phase of the trial.
Following total elimination, it is then recommended to begin the challenge phase where proteins are introduced every 2 weeks to observe any reactions. If there is no improvement of symptoms during the elimination phase, a food allergy is highly unlikely and environmental allergens are believed to be triggers – if this is the case you’ll likely be referred to a Board Certified Veterinary Dermatologist to undertake intradermal skin testing and the formulation of immunotherapy.
Currently, the food elimination trial is the only approved method of diagnosis of adverse food reactions.
You can read more on this topic in my previous post here.
Myths and misconceptions about food allergies
I have previously covered a number of food allergy misconceptions, you can read about these topics here:
Fish based diets are supportive of atopy/dermatological signs of allergies
Rotating diets reduces allergies
However I’ve seen some new ones emerge recently:
- Food allergies can’t happen to puppies/kittens
- You either have environmental allergies or food – never both
- “Processed foods” are the cause of food allergies and feeding raw during growth prevents the development of food allergies
- “Fixing” gut dysbiosis cures food allergies
Let’s discuss why these myths are not only incorrect, they can be harmful.
Food allergies can and do occur under 12 months of age. While it’s uncommon, it’s certainly not rare or unlikely, particularly where dogs are concerned as young/juvenile dogs appear to actually be overrepresented in AFR cases particularly those that have dermatological signs. In cats it’s less common, but still a small proportion of cats develop allergies from 8 months of age.
25-45% of dogs with atopy also have a food allergy. The prevalence is unknown in cats, but is believed to be similar. This is due to the complex metabolic pathways of an allergic response – when the skin is broken or irritated, this widens the junctions between cells and allows more allergens to enter the body, increasing the body’s reactivity and overwhelms the immune system resulting in more and more allergies. It’s why, like mentioned above, placing these pets on a hydrolysed diet can actually help to lower the body’s reactivity as you are reducing their exposure to multiple allergens. This is also why I do not recommend ‘rotating’ different proteins as you are just continuing to introduce different allergens.
All food is processed and there is no evidence that any one type of diet causes allergies. Again, the etiology (cause) of food allergies in animals is not well understood and while there has been many hypotheses on how we can prevent the development of food allergies, no solid evidence has shown any one diet is ‘better’ at preventing the development of allergies (despite a number of problematic and flawed studies claiming the contrary). The only diet that will prevent your pet from having an allergic reaction would be a hydrolysed diet that contains proteins less than 15kDa that cannot be recognised by the body.
Research into whether dysbiosis of the gastrointestinal microbiome is a factor in the development of allergic diseases is required. While dysbiosis can increase gut permeability and lower the body’s tolerance to antigens (allergens), remedying dysbiosis is complex (as your microbiome is as unique as your own fingerprints) and may still not make any difference to the pet’s allergies once they have developed. It may help to reduce their body’s reactivity (like feeding a hydrolysed diet does) but the development of food allergies appears to be multifactorial.
So what can we do?
Nutrition
When looking for a suitable diet for the diagnosis and management of food allergies, we have a few key nutritional factors to consider:
The most important thing to remember with food allergies, is that your pet is allergic to an ingredient or additive and our goals for management are total exclusion (for life) to reduce symptoms and then rebuilding the skin and gut to rehabilitate it back to normal.
So this is why when you look at the list of ket nutrients here, you’ll see that it isn’t just looking at exclusion, but also what a supportive diet should look like to relieve the symptoms.
I also want to stress that your pet isn’t allergic to a type of food – ie, your pet isn’t allergic to “kibble” – but they are allergic to what is in the food. Many pet owners feel disenfranchised with trying diet after diet and your pet having an allergic reaction time and time again so they begin to believe that “all” foods in the same category are an issue. This is why it’s important to conduct a really comprehensive food trial to begin with, then select a diet that we know is free from cross contamination of proteins and allergens. For more on the topic of cross contamination, I recommend reading my post on limited ingredient diets (below) and the associated study here.
Want to learn more about food allergies? Head to @nutritionrvn on Instagram to watch me break it down into highly digestible bites! For all the references and to do your own research, hit read more.
References
Mueller, R.S., Olivry, T. & Prélaud, P. Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats. BMC Vet Res 12, 9 (2016). https://doi.org/10.1186/s12917-016-0633-8
Verlinden, A., Hesta, M., Millet, S., & Janssens, G. P. J. (2006). Food Allergy in Dogs and Cats: A Review. Critical Reviews in Food Science and Nutrition, 46(3), 259–273. https://doi.org/10.1080/10408390591001117
Jackson, H. A. (2023). Food allergy in dogs and cats; current perspectives on etiology, diagnosis, and management. Journal of the American Veterinary Medical Association, 261(S1), S23-S29. Retrieved Aug 24, 2024, from https://doi.org/10.2460/javma.22.12.0548
Jeffers, J. G., Meyer, E. K., & Sosis, E. J. (1996). Responses of dogs with food allergies to single-ingredient dietary provocation. Journal of the American Veterinary Medical Association, 209(3), 608-611. Retrieved Aug 24, 2024, from https://doi.org/10.2460/javma.1996.209.03.608
Mandigers, P., & German, A. J. (2010). Dietary hypersensitivity in cats and dogs. Tijdschr Diergeneeskd, 135(19), 706-710.
Olivry T, Mueller RS. Critically appraised topic on adverse food reactions of companion animals (7): signalment and cutaneous manifestations of dogs and cats with adverse food reactions. BMC Vet Res. 2019;15(1):140. doi:10.1186/s12917-019-1880-2
Jackson H, Murphy KM, Tater K, et al. The pattern of allergen hypersensitivity (dietary or environmental) of dogs with non-seasonal atopic dermatitis cannot be differentiated on the basis of historical or clinical information: a prospective evaluation 2003–2004. In: North American Veterinary Dermatology Forum, Sarasota, Florida, April 7. NAVDF; 2005.
Hemida MBM, Salin S, Vuori KA, et al. Puppyhood diet as a factor in the development of owner-reported allergy/atopy skin signs in adult dogs in Finland. J Vet Intern Med. 2021;35(5):2374-2383. doi:10.1111/jvim.16211
Chesney CJ. Food sensitivity in the dog: a quantitative study. J Small Anim Pract. 2002;43(5):203-207. doi:10.1111/j.1748-5827.2002.tb00058.x
Fossati LA, Larsen JA, Villaverde C, Fascetti AJ. Determination of mammalian DNA in commercial canine diets with uncommon and limited ingredients. Vet Med Sci. 2019;5(1):30-38. doi:10.1002/vms3.125
Images/tables from Small Animal Clinical Nutrition. Chapter 31 – Adverse Food Reactions.
https://www.msdvetmanual.com/integumentary-system/food-allergy/cutaneous-food-allergy-in-animals
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