Why your Dog is Allergic to Everything

Why Your Dog is Allergic To Everything

Have you ever tried food after food after food for your dog, to find that they just seem to be allergic to every protein source on the market? Well, there are a couple of reasons for that…

One is that your dog actually doesn’t have a food allergy – it has an intolerance. 

Two is that your dog has environmental allergies, not food allergies.

But the final reason that most people overlook is… 


The pet food industry has a HUGE problem with ingredients in pet food that ARE NOT LISTED on the dog food label.

Let me shed some light on this epidemic of cross-contamination in the pet food industry and explain to you why your dog with food allergies seems to be allergic to every food on the market. And afterwards – let me give you some recommendations as to which foods may be good options.

How bad is Cross-Contamination REALLY in Pet Food?

As I alluded to earlier. There is a BIG problem with cross-contamination in the pet food industry, and many different research studies have been done looking at this problem. Research studies have shown anywhere from 54-100% of diets tested having proteins within the diet that are not listed on the ingredient label – from raw to canned to kibble – ALL types of dog food have this issue. And yes – even those diets that are labeled as “hypoallergenic” or “limited ingredient”….

Most of the current research we have was done for two reasons:

  1. People were concerned that pets – dogs and cats – were in our pet food.
  2. Veterinary Dermatologists were looking to make excellent recommendations for products to owners for food elimination trials.

Good new is: no research study to date has found dog or cat meat in our pet food.

Bad news is: every single study found that a majority of foods tested contained proteins not listed on the label, and usually proteins not listed were “common allergens”.

Kibble Dog Food Cross-Contamination Research

Kibbled pet foods are probably the biggest problem when it comes to cross-contamination in the industry – between 83-100% of dry dog food in research studies have come back positive for proteins not listed on the label.

kibble cross contamination

In a study done in 2018 that focused on over-the-counter limited ingredient commercially prepared diets, ALL 21 diets tested (100%) had proteins not listed on the label, and one of the diets actually did not contain any proteins listed on the label. The good news in this study was that NONE of the diets contained proteins from dogs, cats, horse, rat, or mice. (Fossati 2018)

Brands included in this 2018 Study were as Follows: Natural Balance L.I.D, Merrick, Canidae, First Mate, Acana, Wild Calling, Nature’s Recipe L.I.D, Nutrish, Nature’s Recipe, Zignature, Wellness, Chicken Soup for the Soul Pet Food, Instinct, Nutro, Canine Caviar Pet Foods, Blue Buffalo. (Fossati 2018)

In a study done in 2013 that looked at 12 different novel protein commercially prepared diets, 10 of the 12 diets (83%) had proteins present in the food that was not listed on the label. The only two diets in which the ingredients on the label matched the PCR and microscopic analysis of the food were the Prescription Hydrolyzed Protein Diet and a Fish-based diet. It is important to note that the study did contain other fish-based diets that were contaminated with other protein sources as well – so we cannot generally state that fish-based diets are not contaminated. (Ricci 2013)

The big thing to take away here is that choosing a “hypoallergenic” diet for a food elimination trial is probably not going to give you the best results if your dog has true food allergies. And just because your dog improves when changing their diet to another brand – it doesn’t mean that it was a true food allergy. It might be related to other issues eg – the lack of mycotoxins in grain-free foods, better ingredient sourcing, better digestibility, food intolerances, or different omega 3 to 6 ratios, etc.

Canned Dog Food Cross-Contamination Research

canned food cross contamination

In comparison to kibbled diets, canned diets have much less cross contamination of protein sources. This might be because of how the diets are manufactured, or possibily due to the machines used to create these diets. However it is important to note that a majority of canned foods are still contaminated with proteins not listed on the ingredient label.

In a study done in 2018 that looked at 11 different novel protein limited ingredient commercially available wet food, they found that 6 of the 11 (54%) of the diets contained proteins that were not listed on the pet food label. None of the vegetarian, fish, horse meat or hydrolyzed protein diets were contaminated with other protein sources. And 1 of the 6 contaminated pet food did not actually contain any of the proteins listed on the label, but instead contained completely different products. (Pagani 2018)

Raw Dog Food Cross-Contamination Research

raw food cross contamination

With the recent influx of people looking to feed raw diets – a question was brought up to if commercial raw diets might be a option for food elimination trials. However according to new research, this doesn’t seem to be the case.

In a study done in 2020 that looked at 18 different raw-meat-based-diets that were commercially available, they found that 11 of the 18 diets (60%) contained proteins that were not listed on the pet food label. The most commonly unlisted protein source in canine diets was lamb. (Cox 2020)

It is possible that due to equipment being used for multiple protein sources – to grind and process meats that contamination may have occurred (even with proper cleaning and sanitation procedures).

How does Cross-Contamination Happen in Dog Food?

There are many different points in the process that may cause issues with cross-contamination. And though we do not know exactly where this occurs with ingredients (because regulation of this is poor), but we can see these points in pet food recalls due to pathogen contamination.

Ingredients are NOT Tested coming into the Facility

third party testing of ingredients entering manufacturing facility

This has happened a couple of times on record in the pet food industry. This is better known as the “supplier issue”, where an ingredient supplier somehow misrepresents their products to the pet food company.

One of the most publicized times this happened was in 2014 with Blue Buffalo when Purina sued them for false advertising after testing the Blue Buffalo foods using a third party lab for “by-products” and the results coming back positive. Blue Buffalo claimed this being a “supplier issue” where basically the company they purchased their meat products from lied to them about what was in the product. Though it is unfortunate that this happened – if Blue Buffalo had been doing their own third-party testing for the purity of ingredient as they entered their facility this may not have occurred. (Blue Buffalo 2014 By Product Recall)

The other largely publicized recall associated with this issue was the Melamine recall from 2007 which affected many different pet food brands including Purina, Diamond, Royal Canin, Natural Balance, Hill’s, Del Monte, Krikland, Sunshine Mill’s, Menu Foods, and more. During this recall Wheat Gluten was contaminated with Melamine in order to cut costs by the ingredient manufacturer and still pass testing by pet food companies for protein minimums. The sad part about this recall is that the results were deadly, many dogs died because companies were not doing full purity checks on their ingredients. (FDA Melamine Pet Food Recall 2007)

Multiple Foods Processed in the Same Facility

Multiple foods made in the same dog food manufacturing facility

Many dog food companies do not actually produce their own products but instead outsource the production to something called a “copacker”. The “copacker” will manufacture multiple different products, and may or may not help with ingredient sourcing, formulation, and even distribution.

The problem with using a copacker is: 

You do not have control over the other foods and the quality of those foods produced in the facility. So though your food may have excellent ingredient sourcing, and quality control testing, other foods that come through the facility MAY NOT. Meaning that even IF a company actually does separate production lines by protein source, it’s possible that the poor sourcing of one company may affect others.

This is much easier to understand if instead of proteins being incorrectly sourced we look at the quality of proteins – aka pathogens – which are heavily regulated by the FDA due to their human health concern. A good example of this is:

In 2012 we had multiple brands recalled due to Salmonella contamination – all of which were manufactured by Diamond Pet Foods including: Diamond Naturals, Kirkland, Wellness, Solid Gold, Natural Balance, Chicken Soup, Taste of the Wild, Canidae, and Apex. (FDA Pet Food Recalls)

Now say one of those brands used a Turkey Meal that was poorly sourced and was actually Chicken Meal. The equipment was separated by protein BUT since one company accidentally used Chicken – all the other foods produced on that line are also potentially contaminated…

Preventing Cross-Contamination

To prevent cross contamination in dog food

The first way cross-contamination can be prevented is by doing rigorous testing of ingredients entering the facility – with will be especially important if a product contains mealed or pre-ground proteins where visual inspection would be extremely difficult to tell these items apart. Full testing should also be performed to check that suppliers are not mixing in other proteins that are not supposed to be there AND are giving the correct composition/cuts of meat.

The second way to prevent cross-contamination is by not using a copacker, but by producing the foods within their own facility, and have their facility ONLY produce foods from their own diet lines. This allows the company more control over the entire manufacturing and production process.

The third thing that can be done is to separate the production of different protein sources onto different equipment. As though cleaning can be done to prevent contamination between recipes if it is possible to still have residue on equipment if cleaning is not done thoroughly enough.

Why Prescription or Homemade for Allergies?

Dog looking at Homemade Dog Food for Food Trial

Many prescription diet companies employ ALL these quality control tests, even doing testing on the final product prior to release to consumers. Companies will use PCR testing on ingredients coming into the facility, then use separate equipment for different recipes. These companies also do not do co-packing or outsource their manufacturing process having full control over the entire process. And this is probably why when tested the Hydrolyzed Prescription Diets did not come positive for other protein sources.

Now, this is not to say that over-the-counter products cannot perform all these same checks. There may be companies that do and will have excellent quality control on their products and production to make sure they do not have issues with cross-contamination. But generally speaking, research has shown us that for a majority of over-the-counter products, this is untrue.

Another way to keep cross-contamination to a minimum is by actually making your dog’s food at home yourself! One of the main benefits of a homemade diet is FULL CONTROL over what goes into the diet. You can easily avoid potential allergens or triggers that your dog has, providing full flexibility. But probably one of the biggest drawbacks of a homemade diet is finding a balanced recipe. If you are looking to step into the world of homemade dog food – make sure to check out my blog post on this topic.

Love, Nikki - The Canine Health Nut and Registered Veterinary Technician

Pagani, Elena et al. “Cross-contamination in canine and feline dietetic limited-antigen wet diets.” BMC veterinary research vol. 14,1 283. 12 Sep. 2018, doi:10.1186/s12917-018-1571-4

Ricci R, Granato A, Vascellari M, Boscarato M, Palagiano C, Andrighetto I, Diez M, Mutinelli F. Identification of undeclared sources of animal origin in canine dry foods used in dietary elimination trials. J Anim Physiol Anim Nutr (Berl). 2013 May;97 Suppl 1:32-8. doi: 10.1111/jpn.12045. PMID: 23639015.

Cox A, Defalque VE, Udenberg TJ, Barnum S, Wademan C. Detection of DNA from undeclared animal species in commercial canine and feline raw meat diets using qPCR. Can Vet J. 2020 Sep;61(9):977-984. PMID: 32879524; PMCID: PMC7424926

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 Feb;5(1):30-38. doi: 10.1002/vms3.125. Epub 2018 Oct 29. PMID: 30375199; PMCID: PMC6376140.

Horvath‐Ungerboeck C., Widmann K. & Handl S. (2017) Detection of DNA from undeclared animal species in commercial elimination diets for dogs using PCR. Veterinary Dermatology 28, 373–e86. – PubMed

Hsieh M., Shih P., Wei C., Vickroy T.W. & Chou C.C. (2016) Detection of undeclared animal by‐products in commercial canine canned foods: comparative analyses by ELISA and PCR‐RFLP coupled with slab gel electrophoresis or capillary gel electrophoresis. Journal of the Science of Food and Agriculture 96, 1659–1665. – PubMed

Okuma T.A. & Hellberg R.S. (2015) Identification of meat species in pet foods using a real‐time polymerase chain reaction (PCR) assay. Food Control 50, 9–17.

Premananda J. (2013) Horse meat scandal‐ a wake‐up call for regulatory authorities. Food Control 32, 569–569.

About the Author: Nikki is a Registered Veterinary Technician (Veterinary Nurse) and Dog Mom with over a decade of experience with dogs and cats. Since graduation from college (BS Biology, Dip. Animal Nutrition, AS Animal Science) she has adopted two mixed breed dogs – Ranger and Ash, and has focused her time learning about pet food and nutrition.

Nikki shares information on a range of dog nutrition topics: from how to create a homemade complete and balanced dog food recipes, to how to choose a dog food. Nikki strives to give dog parents the information they need in order to make the best nutrition decisions for their pup!

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