Dog Food Allergies and Intolerances: Signs, Food Trials and What to Feed

Updated September 2026

Is your dog’s food causing itching, ear problems, or an upset stomach?

Possibly.

But food is only one of several possible causes.

Dogs can develop genuine food allergies and food intolerances, and the signs can include itchy skin, recurrent ear problems, vomiting, diarrhoea and excessive wind.

Those same signs can also be caused by fleas, environmental allergies, infections, parasites and gastrointestinal disease.

That is why I would not start removing chicken, beef, grain and half the contents of your dog’s bowl simply because somebody online says they are common allergens.

If you genuinely suspect a food allergy, the most useful approach is usually a properly controlled veterinary elimination diet.

For my wider feeding guidance, start with my Dog Food & Nutrition Guide.

I am a professional dog walker and pet sitter, not a vet or veterinary nutritionist. This guide is designed to help you understand the terminology and know what questions to ask. Diagnosis belongs with your veterinary team.

Summary

• A food allergy involves an inappropriate immune response to something in the dog’s diet.
• A food intolerance is an adverse reaction that is not recognised as having the same specific immune mechanism.
• In practice, allergies and intolerances can cause similar signs and may be investigated in similar ways.
• Adverse food reactions can cause itching, sore skin, paw licking, recurrent ear trouble, vomiting, diarrhoea, and excessive wind.
• Those symptoms do not prove that food is responsible.
• Dogs can develop a food allergy even after eating the same ingredient for a long time.
• Proteins are common triggers, including ingredients such as beef, chicken, lamb, or dairy.
• Grain-free food is not automatically an allergy diet.
• Blood tests are not considered reliable for diagnosing food allergy in dogs.
• A veterinary elimination diet or food trial is the main diagnostic method.
• A food trial commonly lasts around 6 to 12 weeks.
• During a diagnostic food trial, treats, dental chews, scraps and unapproved flavoured products can invalidate the result.
• Your vet may use a hydrolysed diet or an appropriate novel-protein diet.
• If symptoms improve, your vet may use a controlled food challenge to confirm which foods cause the reaction.
• Do not put a growing puppy or medically unwell dog onto a restrictive DIY diet without veterinary advice.

What is a food allergy in dogs?

A food allergy happens when a dog’s immune system reacts inappropriately to something in their diet.

The trigger is normally a protein.

That protein does not necessarily have to come from meat. Proteins are also present in ingredients such as dairy and wheat.

PDSA explains that dogs can become allergic to ingredients they have eaten before and that food allergy can develop even after a dog has eaten the same food without obvious problems for years.

This is worth remembering because owners sometimes tell me:

“But they have eaten chicken all their life.”

That does not completely rule chicken out.

It also does not mean chicken is responsible.

You still need proper investigation.

What is a food intolerance?

Food allergy and food intolerance are often discussed together, but technically they are not quite the same thing.

A food allergy involves the immune system.

A food intolerance is an adverse response to food without a recognised specific immune mechanism.

The symptoms can overlap considerably, particularly gastrointestinal symptoms, so in everyday veterinary investigation the distinction is not always obvious from the dog’s symptoms alone.

You may also hear broader terms such as:

• adverse food reaction
• food sensitivity
• dietary sensitivity

The label matters less than working out whether food is genuinely contributing to the problem and, if it is, what the dog can safely eat.

What are the signs of food allergy in dogs?

Food allergies can cause skin problems, digestive problems or both.

PDSA lists signs including:

• itchy skin
• itchy ears
• red or sore skin
• itching around the feet, face, ears, chin, tummy or groin
• repeated licking or chewing
• saliva staining
• vomiting
• diarrhoea
• abdominal discomfort
• excessive wind

Some dogs may have predominantly skin signs.

Others may mainly have gastrointestinal problems.

Some have both.

Are itchy ears a sign of food allergy?

They can be.

But they are not proof.

Recurring itchy ears or ear infections can occur alongside allergic skin disease, including food-related allergy.

They can also result from:

• environmental allergies
• ear infections
• ear mites
• foreign bodies such as grass seeds
• other ear disease

PDSA recommends a veterinary assessment if a dog repeatedly scratches its ears or shakes its head, because the underlying cause needs identifying.

Do not repeatedly change the dog’s food every time an ear becomes sore without finding out what is actually happening.

Does paw licking mean my dog is allergic to food?

Not necessarily.

Repeated paw licking can occur with allergic skin disease, but environmental allergy, infection, injury and irritation can also be involved.

Food allergy is one possibility.

It is not the automatic diagnosis.

If your dog repeatedly licks, bites or chews their paws, particularly if the skin becomes red, sore, stained or infected, speak to your vet.

Food allergy is not the only cause of itching

This is probably the most important part of the guide.

A dog starts scratching and it is very easy to blame the food.

Then chicken disappears.

Then beef.

Then wheat.

Then grains altogether.

Six bags of food later, the dog is still scratching.

Environmental allergens such as pollen, grasses and house dust mites can cause similar skin signs. You should also consider fleas and other parasites. Dogs can have more than one allergy at the same time.

My existing Pets and Pollen guide looks at environmental pollen as another possible trigger.

What foods are dogs commonly allergic to?

Dogs can potentially become allergic to various dietary proteins.

PDSA identifies commonly encountered triggers including:

• beef
• chicken
• lamb
• dairy proteins
• wheat

This does not mean those ingredients are inherently bad.

They are also ingredients dogs are commonly exposed to.

I would not remove chicken from every dog’s diet because chicken appears on an allergy list.

Avoid an ingredient only when there is a good reason that individual dog should avoid it.

Is chicken a common dog food allergy?

Chicken can trigger allergies in some dogs.

But “my dog is itchy” does not mean:

“My dog must be allergic to chicken.”

If chicken is suspected, your vet may recommend a diet that removes the relevant protein as part of a controlled trial.

Simply switching from chicken kibble to another supermarket food is not necessarily an adequate diagnostic test.

The new food may contain other ingredients the dog has encountered before.

Treats and chews may also still contain chicken.

Is beef a common dog food allergy?

Beef can also be implicated in food allergy.

The same rule applies.

Don’t diagnose an allergy from an ingredient list alone.

A veterinary food trial is much more useful than repeatedly changing protein sources at random.

Are dogs commonly allergic to grain?

Some dogs can react to ingredients such as wheat.

That does not mean grains as a group are inherently unsuitable for dogs.

PDSA notes that proteins from meat and dairy are commonly involved in food allergy, although wheat can also be a trigger.

“Grain free” and “hypoallergenic” do not mean the same thing.

A grain-free food might still contain a protein your dog reacts to.

Don’t automatically switch to a grain-free diet because your dog has itchy skin.

Does grain-free mean hypoallergenic?

No.

A grain-free food simply excludes particular grains.

It does not guarantee that the food will avoid whichever ingredient is causing a particular dog’s problem.

Likewise, the word “sensitive” on the front of a packet does not diagnose or treat an allergy.

If you are comparing labels, use my How to Read a Dog Food Label in the UK guide once it is published.

What does hypoallergenic dog food mean?

This is an area where marketing can make things unnecessarily confusing.

The BVA’s companion-animal feeding working group notes that the term “hypoallergenic” is not itself regulated in the way many owners might assume. It also distinguishes ordinary limited-ingredient diets from diets using hydrolysed proteins.

If your vet wants a diagnostic food trial, use the diet they recommend rather than choosing a packet because “hypoallergenic” appears in large letters on the front.

What is a hydrolysed dog food?

Hydrolysed diets contain proteins broken into much smaller pieces.

The aim is to make those proteins less likely to be recognised by the immune system as the allergen that triggers a reaction.

These diets are commonly used in veterinary elimination trials, particularly where the dog’s previous diet history is complicated or they have already eaten many different protein sources.

That does not make hydrolysed food necessary for every itchy dog.

It is one diagnostic and management option that your vet may recommend.

What is a novel-protein diet?

A novel protein is essentially a protein source that is genuinely new to that individual dog.

That is why diet history matters.

Something described online as an unusual protein may not be novel for your dog if they have previously eaten it in:

• meals
• treats
• chews
• training food
• table scraps

Your veterinary team needs as complete a food history as possible before deciding whether a novel-protein diet is appropriate.

How is dog food allergy diagnosed?

There is no reliable quick home test.

Your vet will normally start by looking at the whole dog and considering other possible causes of their symptoms.

For an itchy dog that can include checking for or controlling:

• fleas
• mites
• infections
• environmental allergy
• other skin disease

If food remains a possibility, your vet may recommend a properly controlled elimination diet or food trial.

Can a blood test diagnose my dog’s food allergy?

PDSA’s answer is straightforward:

Blood testing is not considered accurate for diagnosing food allergy in dogs.

A properly conducted food trial remains the useful diagnostic method.

I would therefore be cautious about spending money on an online allergy panel that promises to tell you that your dog is allergic to a long list of ingredients from a blood, hair or saliva sample.

What is an elimination diet?

An elimination diet removes ingredients the dog may be reacting to and replaces the normal diet with a carefully selected diet recommended for the trial.

Depending on the dog, the veterinary diet might use:

• hydrolysed protein
• a genuinely novel protein
• another specifically formulated veterinary approach

The important part is not simply buying a different flavour.

The trial needs to be controlled closely enough that the result means something.

PDSA recommends following the veterinary diet exclusively for around 6 to 12 weeks, depending on the individual case and your vet’s instructions.

How long does a dog food trial take?

Typically, you should expect weeks, not days.

PDSA advises a food trial lasting around 6 to 12 weeks.

Skin symptoms can take time to settle, which is one reason a three-day experiment with a new bag of food tells you very little.

Your vet will tell you how long your dog needs to stay on the trial.

Why does the food trial have to be so strict?

Because one unapproved food can muddy the result.

During a proper elimination trial, PDSA advises feeding the prescribed trial food and water only unless your vet specifically approves something else.

That means thinking about more than breakfast and dinner.

Potential problems include:

• dog treats
• dental sticks
• chews
• human food
• scraps
• food offered by visitors
• food used for training
• supplements
• flavoured medications
• another pet’s food

If the dog continues eating the suspected trigger somewhere else in their routine, the diet trial cannot give a clear answer.

What treats can I give during an elimination diet?

Only treats approved by the veterinary team running the trial.

Sometimes the easiest solution is to use a portion of the trial food itself.

PDSA specifically suggests asking your vet or veterinary nurse whether you can use the prescribed diet as treats when needed.

My normal approach to dog training is to match the reward value to the situation.

But when a dog is undergoing a veterinary food trial, the medical restriction takes priority.

My Training Rewards for Dogs guide explains how to choose rewards.

During an elimination diet, use only what your vet has approved.

Dental chews count too

This is an easy one to miss.

Owners may stop all obvious treats but continue giving the usual dental chew every evening.

PDSA specifically includes dental sticks among foods that should be excluded during a controlled food trial unless your vet has approved them.

Medication can matter too.

Ask your vet about flavoured tablets, capsules and supplements rather than assuming they are irrelevant because they are “medicine”.

What if my dog accidentally eats something during the trial?

Make a note of:

• what they ate
• how much
• when it happened

Then tell your veterinary team.

PDSA advises recording accidental foods because they can affect how the trial is interpreted and, in some situations, may mean the trial has to be extended or restarted.

Do not hide it because you think you have “ruined” the test.

Your vet needs the information to interpret what happens next.

Keep a food and symptom diary

This is one of the simplest useful things you can do.

Record:

• exactly what the dog eats
• any accidental food
• itching
• paw licking
• ear irritation
• skin redness
• vomiting
• stools
• excessive wind
• medications
• anything else your vet asks you to monitor

PDSA specifically recommends keeping a diary during a food trial.

It is much easier to discuss progress when you have a record rather than trying to remember whether the dog’s ears were “a bit better about three weeks ago”.

What happens if my dog improves on the elimination diet?

Improvement makes a food-related reaction much more likely.

The next stage may involve a controlled food challenge.

Your vet may advise reintroducing the original diet or selected ingredients and watching for symptoms to return.

A relapse followed by improvement when the elimination diet is restarted provides much stronger evidence that food is responsible than simply feeling that a new food “seems better”.

Do this under veterinary guidance.

Why challenge the dog again if they are better?

Because improvement alone does not always prove what caused the improvement.

During several weeks, other things may also have changed.

For example:

• a skin infection may have been treated
• flea control may have improved
• pollen exposure may have changed
• medication may have been used

A controlled dietary challenge helps determine whether food is really part of the problem.

What if my dog does not improve?

That information is useful too.

Food may not be the main cause.

PDSA advises that if symptoms do not improve by the end of a properly conducted trial, your vet may investigate other causes and treatments.

Don’t automatically move to another random food trial without discussing what happened.

Can dogs have both food and environmental allergies?

Yes.

This is another reason allergy cases can become frustrating.

A dog can improve partially on an elimination diet because food is one trigger while still reacting to something in the environment.

PDSA notes that dogs with food allergy can also have environmental allergic skin disease.

That means partial improvement does not necessarily mean the food trial failed.

Your vet needs to interpret the whole picture.

Is diarrhoea always a food intolerance?

No.

Diarrhoea can result from many things, including:

• sudden diet changes
• scavenging
• parasites
• infections
• stress
• gastrointestinal disease
• medication
• eating too much rich food
• food-responsive conditions
• adverse food reactions

Persistent or recurrent diarrhoea deserves proper veterinary investigation.

Repeatedly switching food every few days can make the situation more confusing, not less.

My dog has a sensitive stomach. Is that an intolerance?

“Sensitive stomach” is a description, not a diagnosis.

A dog may genuinely do better on one diet than another without having an identifiable immune-mediated food allergy.

Chronic gastrointestinal problems can also have other causes.

If your dog repeatedly experiences diarrhoea, vomiting, abdominal discomfort or unexplained weight loss, speak to your veterinary practice rather than relying indefinitely on foods labelled “sensitive”.

Should I change my dog’s food myself first?

If the problem is mild and you simply want to change an otherwise healthy dog’s normal food, gradual transition is reasonable.

But that is different from investigating suspected allergy.

If you genuinely suspect an allergy or intolerance, I would involve your vet before removing multiple ingredients.

Otherwise you can accidentally make future investigation harder.

My How to Change Your Dog’s Food Safely guide covers ordinary diet changes.

Why randomly changing foods can make things harder

Imagine your dog starts itching.

You remove chicken.

Then you try salmon.

Then duck.

Then lamb.

Then a mixed-protein fresh food.

Then several new treats.

A few months later, your vet wants a genuinely novel protein for a diagnostic trial.

Your dog has already eaten nearly everything.

That can make selecting a useful trial diet more difficult.

A planned investigation is much better than dietary roulette.

Should I try a limited-ingredient dog food?

Not automatically.

Limited-ingredient foods can make ingredient tracking simpler in some situations, but that does not make every product suitable for a diagnostic elimination trial.

The BVA emphasises considering the dog’s complete diet history, including snacks, treats, and medications, when investigating dietary sensitivity.

If the purpose is diagnosis rather than simply feeding preference, use the food your veterinary team recommends.

Does homemade food help dogs with allergies?

Not automatically.

Home cooking gives you control over ingredients, but that does not guarantee nutritional balance.

A homemade elimination diet may sometimes be formulated for a specific veterinary purpose, but I would not invent one myself from meat, vegetables and supplements.

BSAVA recommends obtaining appropriate veterinary nutritional advice for home-prepared diets so that they remain nutritionally complete and balanced.

What about raw food for allergies?

Raw food is not automatically an allergy treatment.

A dog can react to a protein whether that ingredient is raw, cooked, wet or dry.

Changing preparation method does not necessarily remove the allergen.

Raw diets also bring separate hygiene and nutritional considerations.

Do not change a dog onto raw food simply because itching has been labelled an “allergy” online.

Can puppies have food allergies?

Yes, food allergies can occur in younger dogs.

But puppies also have specific nutritional requirements for growth.

Do not put a growing puppy onto a highly restrictive homemade diet without veterinary guidance.

PDSA notes that food allergies can occur at any age and are often first seen in younger dogs.

My Puppy Feeding Guide should remain the main owner for ordinary puppy feeding.

Food allergy and dog treats

Treats deserve particular attention.

My live guide, Dog Treats: How to Choose the Right Treats for Your Dog, already explains that a dog with suspected allergies may need a strict veterinary diet and that ordinary treats can interfere with the investigation.

What about training a dog on a restricted diet?

You can still use reward-based training.

The reward simply needs to fit the dog’s medical diet.

For some dogs, pieces of their prescribed food can be used.

Other rewards can include:

• access to sniffing
• play
• toys
• movement
• calm attention
• another activity the dog enjoys

My Training Rewards for Dogs guide explains why food is only one possible reward.

If your dog is on a food trial, check all edible rewards with your veterinary team.

Food allergies when your dog has a walker or pet sitter

This is where clear instructions really matter.

If your dog is undergoing a food trial or has a confirmed food allergy, make sure anyone caring for them knows:

• exactly which food they may eat
• the precise amount
• which treats are permitted
• which treats are forbidden
• whether training food is allowed
• whether medication is flavoured
• what symptoms to watch for
• what to do if the dog accidentally eats something else

My Finchley Dog Walker Welcome Pack already asks clients to tell me about allergies, intolerances, previous reactions, new foods and dietary changes.

How I handle restricted diets during walks and house sitting

If a client tells me their dog is on a restricted or veterinary diet, I follow it.

I do not decide:

“They’ve been good, one normal biscuit won’t matter.”

If the dog is undergoing a diagnostic food trial, one ordinary treat can matter.

For walks, I can use owner-approved food or non-food rewards where appropriate.

For house sitting, I follow the agreed feeding routine and keep other food out of reach.

That continuity is particularly useful for dogs whose diet needs to remain tightly controlled while their owner is away.

Pet and House Sitting in Finchley and North London

When should I contact my vet?

Book an appointment if your dog has persistent or recurring:

• itching
• paw chewing
• ear trouble
• red or sore skin
• recurrent skin infections
• vomiting
• diarrhoea
• excessive wind
• abdominal discomfort
• unexplained weight loss

Those signs may or may not be caused by food.

The point of the appointment is to work out what is happening rather than guessing.

When is an allergic reaction an emergency?

Chronic food allergy usually presents very differently from a sudden severe allergic reaction.

Seek urgent veterinary advice if your dog develops signs such as:

• difficulty breathing
• collapse
• severe weakness
• sudden marked facial swelling
• rapidly worsening symptoms

PDSA advises contacting a vet immediately for signs of an acute allergic reaction rather than waiting to see whether they improve.

For broader emergency preparation, use my Dog Health & First Aid Guide.

My simple checklist if you suspect food allergy

Do not diagnose it from one symptom

Itching and diarrhoea have many possible causes.

Write down everything your dog eats

Include meals, treats, chews, scraps, supplements and flavoured medication.

Speak to your vet

Let them assess other likely causes.

Do not randomly remove several ingredients

That can make future investigation harder.

If your vet recommends a food trial, follow it strictly

“No treats” really does mean no unapproved treats.

Keep a diary

Record food, skin, ears and gastrointestinal signs.

Do not rely on an online allergy test

A properly conducted diet trial is much more useful.

Think long term only after you know the cause

Once the trigger is identified, the goal is a nutritionally complete diet the dog can eat safely and consistently.

Frequently asked questions

What is the difference between a dog food allergy and intolerance?

A food allergy involves an inappropriate immune response to a dietary component.

A food intolerance is an adverse food reaction without the same recognised specific immune mechanism.

They can produce similar symptoms and are often investigated using similar dietary trials.

What are the most common signs of dog food allergy?

Itchy skin, itchy ears, red or sore skin, paw licking, recurrent skin or ear problems, vomiting, diarrhoea, abdominal discomfort and excessive wind can occur.

None of these signs proves that food is responsible.

What foods are dogs most commonly allergic to?

Food allergies tend to involve proteins from foods the dog has previously encountered. PDSA lists ingredients such as beef, chicken, lamb, dairy and wheat among recognised triggers.

Can a dog suddenly become allergic to food they have eaten for years?

Yes.

Previous tolerance does not completely rule out a later food allergy.

How do I test my dog for food allergies?

The main diagnostic method is a veterinary elimination diet or food trial, followed where appropriate by dietary challenge.

Are dog food allergy blood tests accurate?

PDSA states that blood tests are not accurate for diagnosing food allergy in dogs.

How long does a dog food trial take?

A veterinary elimination diet commonly lasts around 6 to 12 weeks.

Follow the duration recommended for your individual dog.

Can my dog have treats during an elimination diet?

Only treats specifically approved as part of the trial.

Ordinary treats, dental chews and table scraps can interfere with the result.

What is hydrolysed dog food?

It contains protein broken into very small pieces so it is less likely to trigger an immune response. Veterinary hydrolysed diets are commonly used in food trials.

What is a novel-protein diet?

It uses a protein source the dog has not previously eaten.

What counts as novel depends on that individual dog’s diet history.

Is grain-free dog food good for allergies?

Grain-free does not mean hypoallergenic.

Dogs can react to animal proteins as well as other dietary ingredients.

Is chicken always the cause of dog food allergy?

No.

Chicken can be an allergen for some dogs, but many dogs eat it without problems.

Diagnosis should be based on the individual dog rather than internet lists.

Can food allergy cause ear infections?

Allergic skin disease can contribute to recurrent ear problems.

However, ear problems also have many other causes, so veterinary examination is important.

Can food allergies be cured?

The reaction is generally managed by identifying and avoiding the dietary trigger rather than curing the underlying tendency to react.

Can I make my own allergy diet?

Don’t create a restrictive long-term diet on your own.

If a home-prepared elimination diet is considered appropriate, ask your vet about qualified veterinary nutritional guidance.

Final thoughts

Food allergies and intolerances are real.

But so are fleas, pollen, skin infections, ear disease and gastrointestinal problems.

That is why I would not start by banning a long list of ingredients.

Start with the dog.

Look at the symptoms.

Write down what they actually eat.

Speak to your vet.

And if a controlled food trial is recommended, treat it as a proper diagnostic test rather than simply another food change.

Be strict about treats.

Keep a record.

Give it enough time.

Then let the results guide what happens next.

Once you know what your dog genuinely needs to avoid, feeding usually becomes much simpler than endlessly trying another packet labelled “sensitive”.

• Dog Food & Nutrition Hub
• First aid for dogs Hub
• How to Choose a Dog Walker
• Pollen Allergies in Dogs: Signs, Checks and When to See a Vet
• Senior Dog Nutrition: A Practical Guide to Feeding Your Older Dog

This guide provides general information about adverse food reactions in dogs. It cannot diagnose a food allergy, food intolerance, skin condition or gastrointestinal disease. Speak to your veterinary practice if your dog has persistent itching, ear problems, vomiting, diarrhoea, unexplained weight change or another health concern. Veterinary guidance is particularly important before using a restrictive or elimination diet in puppies, pregnant dogs, dogs with existing medical conditions or dogs taking medication.