Does Your Dog Have a Food Intolerance? Signs, Testing and Elimination Diets Explained
Does Your Dog Have a Food Intolerance? Stop Guessing and Start With a Structured Elimination Diet Plan
Is your dog constantly licking their paws, struggling with loose stools, experiencing recurring ear problems or producing enough wind to clear the room?
You may have started to wonder whether something in their food is responsible.
Perhaps you have already removed chicken, switched to grain-free food, tried a novel protein, added supplements or purchased a food intolerance test. Your dog may improve for a few days or weeks, only for the symptoms to return again.
This is where many owners become stuck.
The problem is not necessarily that you have chosen the “wrong” ingredient. The problem is that repeatedly changing food without a structured plan makes it almost impossible to work out what is actually helping and more importantly WHAT is causing the issues.
Symptoms associated with food intolerance can also be caused by parasites, infections, environmental allergies, stress, inappropriate fat or fibre levels, medication and underlying gastrointestinal disease.
The most reliable way to investigate a suspected food intolerance is not another random food change or a hair and saliva test. It is a carefully planned elimination diet followed by the controlled reintroduction of foods.
If you are unsure where to start, a Focused Nutrition Support Consult can help you build a clear, practical elimination diet plan around your individual dog.
Book a Focused Nutrition Support Consult
What Is a Food Intolerance in Dogs?
A food intolerance is an adverse reaction to a food or ingredient that does not necessarily involve the immune system.
Your dog may struggle to tolerate:
A particular ingredient
A specific protein source
A food that is too high in fat
A certain type or amount of fibre
Lactose or another poorly digested component
A food containing several rich ingredients
A sudden dietary change
A portion that is too large
For example, a dog may develop diarrhoea after eating a particularly fatty food. This does not automatically mean the dog is allergic to the meat in that food. They may simply struggle to digest the amount of fat being fed.
Another dog may tolerate a small amount of an ingredient but develop wind, bloating or loose stools when it is included in larger quantities.
The term “food intolerance” is often used broadly. In many cases, it is difficult to determine the exact biological mechanism behind the reaction. Veterinary professionals may therefore use the wider term adverse food reaction.
This is why simply looking at a list of ingredients rarely provides an answer. Your dog’s complete diet history, symptoms, veterinary findings, treats, supplements and previous foods all need to be considered.
Food Intolerance vs Food Allergy in Dogs
Food intolerance and food allergy are often treated as the same thing, but there are important differences.
What is a dog food allergy?
A food allergy involves an inappropriate immune response to something within the diet, usually a protein. They are much less common than intolerances.
A dog will normally have been exposed to the protein previously. This means they can potentially develop a reaction to an ingredient they have eaten successfully for months or even years.
Possible signs of a food allergy include:
Persistent itching
Paw licking or chewing
Red or inflamed skin
Facial swelling
Hives
Recurrent ear inflammation
Head shaking
Vomiting or diarrhoea
Non-seasonal skin flare-ups
What is a food intolerance?
A food intolerance does not necessarily involve the immune system. It may relate to the way the dog digests or tolerates a food, its nutrient profile or the quantity being fed.
Signs are often more gastrointestinal and may include:
Excessive flatulence
Bloating
Abdominal discomfort
Loose or inconsistent stools
Mucus in the stool
Increased bowel movements
Vomiting
Regurgitation
Lip licking or gulping
Reduced appetite
However, the symptoms of food allergy and food intolerance can overlap considerably.
You cannot reliably diagnose either condition by looking at symptoms alone. A structured elimination diet is needed to investigate whether food is contributing to the problem.
Signs Your Dog May Have a Food Intolerance
Food intolerance can present differently in every dog. Some dogs experience mainly digestive symptoms, while others have a combination of digestive, skin and ear problems.
Digestive signs
Possible digestive signs include:
Recurring soft stools
Diarrhoea
Excessive wind
Bloating
Mucus in the stool
Frequent bowel movements
Vomiting or regurgitation
Changes in appetite
Drooling, gulping or lip licking
These symptoms do not always mean food intolerance.
Dogs experiencing lip licking, gulping, vomiting or discomfort around meals may also need to be assessed for reflux.
Read Acid Reflux in Dogs: Signs, Causes and Diet Support.
Skin and ear signs
Possible skin and ear signs include:
Itchy paws
Paw chewing
Redness between the toes
Recurrent ear inflammation
Head shaking
Itchy skin
Hot spots
Excessive licking
Repeated skin infections
Paw chewing is not always caused by food. Environmental allergies, parasites, injury, pain, yeast and behavioural factors must also be considered.
Read more in Why Is My Dog Biting Their Paws?.
Anal gland and stool problems
Dogs with recurring loose or inconsistent stools may also struggle with anal gland problems.
However, anal gland issues are not proof of a food intolerance. Fibre intake, stool volume, weight, gland position, skin disease and inflammation can all play a role.
Read Why Is My Dog Scooting Their Bum?.
If your dog has several overlapping symptoms, a focused consultation can help you organise their diet history and identify the most appropriate nutritional next step.
Book a Focused Nutrition Support Consult
These Symptoms Do Not Automatically Mean Food Intolerance
It is easy to assume food is the problem when your dog is itchy, gassy or experiencing repeated digestive upsets.
However, recurring diarrhoea, vomiting, itching or weight loss can also be associated with:
Parasites
Giardia
Bacterial or fungal infections
Environmental allergies
Flea allergy
Pancreatitis
Exocrine pancreatic insufficiency
Chronic enteropathy
Liver or kidney disease
Vitamin B12 deficiency
Medication side effects
Stress or anxiety
Abrupt food changes
Excessive treats
An unbalanced diet
Your veterinarian should investigate persistent, severe or worsening symptoms before food intolerance is assumed.
Seek veterinary advice promptly if your dog is losing weight, passing blood, vomiting repeatedly, becoming lethargic, refusing food, showing signs of pain or developing swelling around the face or mouth.
A nutrition consultation does not replace veterinary investigation. It can, however, help you implement the nutritional part of your dog’s plan once serious or treatable medical causes have been considered.
Why Dog Food Intolerance Tests Are Inaccurate
Hair, saliva and blood-based food sensitivity tests are widely advertised to dog owners.
They often promise to identify long lists of foods that your dog should avoid. This can appear much easier than carrying out an elimination diet.
Unfortunately, these tests cannot reliably determine whether a particular food is responsible for your dog’s symptoms.
A review of the available veterinary evidence concluded that elimination diets followed by food challenges remain the most reliable way to diagnose adverse food reactions. Hair, saliva and serum antibody tests have not demonstrated sufficient accuracy to replace this process.[1]
A 2019 study assessed serum and saliva tests using samples from dogs without signs of food allergy. The tests frequently produced positive results despite the dogs being clinically healthy.[2]
Another study examined food-specific antibodies in the saliva and blood of dogs with confirmed adverse food reactions and healthy dogs. The tests could not reliably distinguish between the groups.[3]
Commercial hair and saliva testing has also shown poor repeatability and an inability to consistently differentiate allergic dogs from non-allergic dogs.[4]
A separate investigation submitted both genuine and artificial samples to a direct-to-consumer pet allergy testing company. Positive results were produced for samples that had not come from an animal, and the findings were inconsistent when testing was repeated.[5]
These tests can be misleading because:
A positive result may simply show previous exposure.
Antibodies do not prove that eating the food causes symptoms.
Healthy dogs can receive several false positive results.
Different tests can produce completely different food lists.
Repeat tests may not produce the same answer.
Owners may unnecessarily remove large numbers of ingredients.
Restricted home-prepared diets may become nutritionally unbalanced.
If you have already bought a food intolerance test, do not immediately remove every food listed.
Instead, your dog’s diet history, clinical signs, veterinary results and previous responses to food should be reviewed together.
A Focused Nutrition Support Consult can help you move away from unreliable lists and towards a controlled elimination diet that gives you useful information.
The Gold Standard: An Elimination Diet for Dogs
The recognised gold standard for investigating a suspected food allergy or intolerance is an elimination diet followed by a dietary challenge.[1][6]
An elimination diet removes previously fed ingredients and replaces the dog’s usual food with one carefully selected trial diet.
The trial diet may be:
A veterinary hydrolysed diet
A veterinary elemental diet
A carefully selected novel-protein diet
A professionally formulated home-cooked elimination diet
Hydrolysed diets
Hydrolysed diets contain proteins that have been broken into smaller components. This reduces the likelihood of the immune system recognising and reacting to the original protein.
Veterinary hydrolysed diets also offer better control over ingredients than many retail foods.
Novel-protein diets
A novel-protein diet uses a protein the dog has genuinely never eaten before.
This can be difficult because many dogs have eaten a wide range of proteins through complete foods, treats, chews, table scraps, supplements and flavoured medication.
Retail foods labelled “hypoallergenic”, “sensitive” or “limited ingredient” are not automatically suitable for an elimination diet.
Research has identified discrepancies between the ingredients declared on some pet food labels and the animal proteins detected within the food. Potential cross-contact can make the results of an elimination trial harder to interpret.[7]
This is one reason why repeatedly buying different “sensitive” retail foods often fails to provide a clear answer.
Read my full guide: Elimination Diet for Dogs: How to Find Food Allergies and Intolerances.
How Long Should an Elimination Diet Last?
The length of the trial depends on your dog’s symptoms, medical history and response.
Digestive symptoms may improve relatively quickly. Skin symptoms, including itching, paw licking and recurring ear inflammation, may take longer.
A review of elimination-diet studies found that feeding a restrictive diet for approximately eight weeks identified more than 90% of dogs with food-related skin symptoms.[6]
As a practical guide, many dogs will need around six to eight weeks on the agreed diet. Some dogs may need a longer trial under veterinary guidance.
During this period, the plan must be followed consistently.
This means checking:
Treats
Dental chews
Table scraps
Lick mats
Supplements
Flavoured medication
Training rewards
Food provided by walkers or relatives
Anything the dog scavenges
Even occasional extras can interfere with the trial.
A structured plan should also include a symptom diary covering:
Stool quality
Vomiting or regurgitation
Wind and bloating
Itching
Ear symptoms
Paw licking
Appetite
Medication
Accidental food exposure
This level of organisation is often the difference between a useful elimination diet and another inconclusive food change.
Why the Food-Challenge Stage Matters
Improvement on an elimination diet is encouraging, but it does not automatically prove that the original symptoms were caused by food.
Symptoms may also improve because:
A secondary infection was treated.
Medication began working.
Parasite control improved.
Environmental allergen exposure changed.
Rich treats and chews were removed.
Fat or fibre levels became more appropriate.
The feeding routine became more consistent.
To gather stronger evidence, the original food or individual ingredients should be reintroduced in a controlled way.
Research supports the return of clinical signs following reintroduction as an essential part of diagnosing a food reaction.[8]
When symptoms return after an ingredient is introduced and improve again after it is removed, the link becomes much clearer.
Without this stage, you may know that your dog is better on the trial diet, but you may not know why.
The challenge phase should be planned carefully, particularly for dogs with severe symptoms, chronic gastrointestinal disease or other diagnosed conditions.
Stop Food Hopping and Start With a Plan
Changing from chicken to salmon, then lamb, then raw food and finally a grain-free sensitive food is not an elimination diet.
Each change adds more ingredients to your dog’s diet history and makes the problem harder to investigate.
A properly structured elimination plan should consider:
Everything your dog has previously eaten
Their current symptoms
Veterinary findings
Medication
Calorie requirements
Fat and fibre tolerance
Other medical conditions
The most appropriate trial diet
Suitable treat alternatives
Transition speed
Symptom tracking
Food reintroduction
The aim is not to remove as many foods as possible.
The aim is to identify what your dog genuinely tolerates and create a practical, nutritionally appropriate long-term plan.
Book a Focused Nutrition Support Consult
You do not need to keep guessing which food to try next.
During a Focused Nutrition Support Consult, I will review your dog’s complete diet history and help you create a structured elimination diet plan.
Depending on your dog’s needs, we can cover:
The most appropriate type of elimination diet
Whether a hydrolysed or home-cooked option should be considered
How to transition onto the trial diet
Which treats, chews and supplements must be removed
How much food your dog requires
Which symptoms you need to record
How long the elimination phase should continue
How to approach food reintroduction
When further veterinary support may be required
This consultation is ideal for owners who:
Have already tried several foods without a clear answer
Feel overwhelmed by conflicting online advice
Have purchased an intolerance test and do not know what to do with the results
Need help choosing an appropriate elimination diet
Want a step-by-step plan rather than another food or supplement recommendation
A focused plan can save you time, reduce unnecessary food changes and help you collect information that is genuinely useful.
Book your Focused Nutrition Support Consult with The Canine Dietitian
Final Thoughts
Your dog may have a food intolerance, but symptoms such as itching, wind, loose stools, ear problems and paw licking are not enough to confirm it.
Commercial food sensitivity tests may provide impressive-looking reports, but they cannot reliably identify which foods are causing your dog’s symptoms.
A carefully controlled elimination diet followed by food challenges remains the most useful approach.
Stop buying another bag of food and hoping for a different result.
Stop removing ingredients without knowing whether they are relevant.
Start with a structured plan built around your individual dog.
Book a Focused Nutrition Support Consult
Related Reading
References
1. Olivry T, Mueller RS and Prélaud P. Critically appraised topic on adverse food reactions of companion animals: can we diagnose adverse food reactions in dogs and cats with in vivo or in vitro tests? BMC Veterinary Research. 2017;13:275.
Read the study
2. Lam ATH, Johnson LN and Heinze CR. Assessment of the clinical accuracy of serum and saliva assays for identification of adverse food reaction in dogs without clinical signs of disease. Journal of the American Veterinary Medical Association. 2019;255(7):812–816.
View on PubMed
3. Udraite Vovk L, Watson A, Dodds WJ, Klinger CJ, Classen J and Mueller RS. Testing for food-specific antibodies in saliva and blood of food-allergic and healthy dogs. The Veterinary Journal. 2019;245:1–6.
View on PubMed
4. Coyner K and Schick A. Hair and saliva test fails to identify allergies in dogs. Journal of Small Animal Practice. 2019;60(2):121–125.
View on PubMed
5. Bernstein JA, Diesem N, Kvitko-White H and Meurs K. Hair and saliva analysis fails to accurately identify atopic dogs or differentiate real and fake samples. Veterinary Dermatology. 2019;30(2):105-e28.
Read the study abstract
6. Olivry T, Mueller RS and Prélaud P. Critically appraised topic on adverse food reactions of companion animals: duration of elimination diets. BMC Veterinary Research. 2015;11:225.
Read the full study
7. Olivry T and Mueller RS. Critically appraised topic on adverse food reactions of companion animals: discrepancies between ingredients and labelling in commercial pet foods. BMC Veterinary Research. 2018;14:24.
Read the full study
8. Shimakura H, Uchiyama J, Saito T, Miyaji K, Fujimura M and Masuda K. Results of food challenge in dogs with cutaneous adverse food reactions. Veterinary Dermatology. 2021;32(4):293-e80.
View on PubMed
