Facts About Food Allergies

Most of this information is already here in The Food Group, but I thought I would put it all together in one discussion for easy access. I hope that you regular Food Groupies will remember that it's here and use it when a newbie pops in with questions about food allergies.


Fact 1: Food Allergies Are Relatively Rare.

There is a 1 in 10 chance that any dog will have some kind of allergy. There is a 1 in 100 chance that any dog will have an allergy to any type of food. Food allergies are the least common type of allergy in dogs, ranking behind flea allergies and Atopic Dermatitis, (often called "skin allergies", "seasonal allergies", or "environmental allergies")


Fact 2: Food Allergies Take Time to Develop.

It is extremely rare for a puppy under the age of 7 months to have a food allergy. It usually takes 6 months to a year of eating the same food repeatedly for a dog to develop an allergy to it, with symptoms most often appearing between 1-2 years of age. This is one reason why it's a good idea to rotate different protein sources in your dog's diet. 


Fact 3: Vomiting And/Or Diarrhea Are NOT Symptoms of a Food Allergy.

The symptoms of any allergy in a dog take the form of itching and scratching; rubbing the face, chewing, biting, or licking the paws, itching, scratching & biting the groin, axilla, and base of the tail, red inflamed eyes,  skin and/or ear infections. The most common, and usually the first, sign of allergies in dogs is licking or chewing the paws. I have seen one reliable article stating that in a very small percentage of dogs with food allergies, GI symptoms may also appear, but even there, they are always accompanied by dermatological issues.

Gastrointestinal symptoms such as vomiting, regurgitation, loose stools or diarrhea may be signs that your dog has an intolerance to a particular food or combination of foods, but a food intolerance has nothing at all to do with an allergy. An allergy is an incurable disease of the immune system. A food intolerance means something does not agree with your dog's digestive system. There is a big difference.

(Note: Ongoing or severe GI symptoms can also be indicative of a digestive disease, so in those cases, please consult your vet.)


Fact 4: Dogs Are Allergic to A Specific Food, Not a Brand of Food Or A Type of Feeding.

If there is a food allergy, this means that the dog is allergic to one or more specific ingredients, not to all of the ingredients in a particular type of food. The most common food allergens for dogs are corn, wheat, beef, chicken, and soy. If your dog is allergic to chicken, he is allergic to all chicken in every form, sold by every manufacturer....raw chicken, cooked chicken, the chicken in Purina and the chicken in Orijen. It is the particular combination of protein molecules within a specific food that trigger the allergic reaction, not the brand of dog food or the method of cooking.

Also, food allergies are very specific. Your dog can be allergic to chicken but not to turkey, because the protein molecules (and therefore the antibodies) are very different. And your dog cannot be allergic to something that he has never eaten. There has to have been prior exposure to develop an immune response to something. 


Fact 5: There is No Medical Test for Food Allergies, and Switching Brands Won't Help.

Blood tests for food allergies have been proven to be extremely unreliable. Scratch tests are not done for foods.

In order to determine if your dog has a food allergy, you must do food trials. This means you eliminate corn, wheat, beef, and chicken from your dog's diet and feed a limited ingredient diet with one "novel" protein source (something the dog has not been eating on a regular basis, like rabbit or duck) and one starchy carbohydrate (often oatmeal, potatoes, or some type of legumes) for a period of 3 months. (It is not possible for a dog to be allergic to a food he has never eaten.) This also includes all treats, everything that the dog consumes. If the symptoms go away, you then gradually add the chicken back in. If that's okay you add the beef back in, etc., until you have determined what the allergens are. Food trials take many months and are very restrictive.

If you just change your brand of foods, and the dog's symptoms happen to go away, what does that tell you? Which ingredient was the culprit? What can he eat now?


Fact 6: Certain Types of Inhalant Allergies Can be Triggered by Poor Quality Food.

Storage mites are dust-mite type micro-organisms that are believed to be as much to blame for asthma attacks in children as dust-mites, and storage mite allergies are increasing in children...and dogs. Storage mites live in dry cereal-type foods with a lot of particulate matter. The longer the shelf life of a product, the greater the chance that it contains storage mites. The more tightly sealed and impermeable the packaging, the less likely it is to contain storage mites. A dog who is eating a grocery store brand that sits for a year on a warehouse shelf in a paper bag might well show great improvement in itching and scratching if you switched him to a premium dog food. Did he have food allergies...or storage mite allergies?

A poor Omega 6:3 ratio can also contribute to allergy symptoms, although it won't cause them. You want a food that is high in Omega 3 fatty acids DHA and EPA from fish, and an Omega 6:3 ratio of not more than 5:1. 3:1 or lower would be best.


Fact 7: Rx Diets Prescribed by the Vet Are Garbage and Should Be Avoided at all Costs.

Rx diets do not contain any magic ingredients that will cure your dog's allergies...if he even has any allergies. They are outrageously priced crap in a can/bag that your dog doesn't need..you can feed an alternative diet cheaper, and with healthier ingredients. Please use this link to learn more about why you should say no when your vet prescribes an Rx diet.


Fact 8: Seasonal Allergies Are Never Caused by Food.

This one should be self-explanatory, but let's go over it to make sure. If your dog is allergic to his food, he would be having symptoms all year round, right? So if he suddenly develops allergy symptoms, especially if it's spring or late summer/early fall, don't listen to all the people who tell you to change his food. Chances are great that if he's allergic, it's an allergy to pollen or mold...which are ten times more common than food allergies. Try conservative treatments as advised by your vet and wait until there's a pattern in terms of time of year. Severe allergic reactions always require immediate treatment.


Hope I covered everything. Bottom line, food allergies are nowhere near as common as people think they are, and misinformation is abundant. I hope this helps.






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  • Thanks for this. I am saving it to my hard drive.
  • Thanks for taking the time to post this Karen! I'm going to print this off right now!!!
  • This is great - thank you!
  • Here's a great article from the Merck Veterinary Manual, with an especially good explanation of food trials:
    Food allergy is ~10% as common as atopy in dogs and about as common as atopy in cats. The history is that of a nonseasonal pruritus, with little variation in the intensity of pruritus from one season to another in most cases. Most reports do not suggest a breed predilection; however, one report indicated an increased relative risk in Labrador Retrievers, West Highland White Terriers, and Cocker Spaniels. Food hypersensitivities have been reported in Soft Coated Wheaten Terriers in association with protein-losing enteropathy and nephropathy. The age of onset is variable, from 2 mo to 14 yr old. One report indicated that most food allergies begin at <12 mo of age.
    The distribution of pruritus and lesions varies markedly between animals. Ear canal disease that manifests as pruritus and secondary infection with bacteria (usually Staphylococcus intermedius , Pseudomonas spp , Proteus spp , or Escherichia coli ) or yeast ( Malassezia pachydermatis ) are common and may be the only presenting complaint. Other patterns seen include blepharitis, generalized pruritus, generalized seborrhea, a papular eruption, or a distribution pattern that may mimic that of atopy (feet, face, and ventrum) or flea allergy dermatitis (dorsal lumbosacrum and hindlegs). The most common areas of involvement include the ears, feet, inguinal region, axillary area, proximal anterior forelegs, periorbital region, and muzzle. The degree of pruritus is usually moderate to severe. Response to glucocorticoids varies from poor to excellent.
    There is no reliable diagnostic test other than a strict food elimination diet. Serologic testing and intradermal testing for food allergens have proved unreliable. The ideal food elimination diet should be balanced and nutritionally complete and not contain any ingredients that have been fed previously to the animal. Many diets contain novel protein or carbohydrate sources (eg, lamb and rice). However, it is often misunderstood that if any previously fed ingredient is present in the elimination diet, the animal may be allergic to the novel ingredient and the diet trial will be a failure. The key point in any food elimination diet trial is that only novel food ingredients can be fed.
    The trial diet should be fed for up to 3 mo. If marked or complete resolution in the pruritus and clinical signs occurs during the elimination diet trial, food allergy can be suspected. To confirm that a food allergy exists and that the clinical improvement was not just coincidental, the animal must be challenged with the previously fed food ingredients and a relapse of clinical signs must occur. The return of clinical signs after challenge is usually between 1 hr and 14 days, although it is sometimes within 3 days. Once a food allergy is confirmed, the elimination diet should be reinstituted until clinical signs resolve, which usually takes <14 days. At this point, previously fed individual ingredients should be added to the elimination diet for a period of up to 14 days. If pruritus recurs, the individual ingredient is considered positive for having a causative role in the food allergy. If pruritus does not recur the individual ingredient is not considered important in causing the clinical signs.
    The number of offending food allergens varies from 1-5 ingredients. The most frequently identified causative allergens in canine food allergy include beef, chicken, eggs, corn, wheat, soy, and milk. Once the offending allergens are identified, control of the food allergy is by strict avoidance. Concurrent diseases (such as atopy or flea allergy) may complicate the identification of underlying food allergies. Infrequently, a dog will react to new food allergens as it ages.
  • Great, great information. Thanks so much, Karen!
  • Thanks Karen, what a great idea!

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