If your dog is constantly scratching, licking their paws or dealing with an upset stomach, food could be part of the problem. Food allergies are less common than many owners think, but they are a real cause of itchy skin and digestive trouble in dogs, and they are often confused with intolerances and environmental allergies.
This guide explains what a dog food allergy is, the symptoms to look out for, the foods most often involved, and how vets confirm a food allergy. It also gives you an honest look at what at-home tests can and can't tell you.
In this guide
- What is a dog food allergy?
- Symptoms of food allergies in dogs
- When to see a vet straight away
- What are dogs most commonly allergic to?
- Is it food, or something else?
- How food allergies are diagnosed: the elimination diet
- Can a test diagnose a food allergy?
- Living with a dog with food allergies
- Frequently asked questions
What is a dog food allergy?
A food allergy happens when your dog's immune system mistakes a normal ingredient, usually a protein, for a threat and reacts to it. That immune reaction is what causes the itching, inflammation and digestive upset.
Food allergies are one type of adverse food reaction. The other main type is a food intolerance, which doesn't involve the immune system. An intolerance is a problem digesting or processing a food, such as lactose in milk, and it mainly causes stomach and bowel symptoms rather than itchy skin.
| Food allergy | Food intolerance | |
|---|---|---|
| Involves the immune system? | Yes | No |
| Typical triggers | Proteins such as beef, dairy, chicken or wheat | Ingredients the gut struggles with, such as lactose or fatty foods |
| Main symptoms | Itchy skin, paw licking, ear problems, sometimes vomiting or diarrhoea | Diarrhoea, vomiting, wind, bloating |
| Amount needed to cause a reaction | Even small amounts | Often depends on how much is eaten |
A food allergy usually develops to something your dog has eaten many times before, not to a new food. That's why a dog can eat the same food happily for years and then start reacting to it. For a closer look at the difference, read Food Allergies vs. Adverse Food Reactions in Dogs.
Symptoms of food allergies in dogs
The most common sign of a food allergy is itching that carries on all year round rather than coming and going with the seasons. Symptoms can affect the skin, the gut or both.
Skin and coat symptoms
- Constant scratching, rubbing or chewing
- Licking or chewing the paws
- Red, inflamed skin, especially on the face, ears, armpits, belly, groin and around the bottom
- Repeated ear infections or itchy, smelly ears
- Recurring skin infections, hot spots or hair loss from over-grooming
- Scooting or licking around the bottom
Digestive symptoms
- Vomiting
- Diarrhoea or soft stools
- Going to the toilet more often than usual
- Excess wind or a gurgling tummy
Some dogs only show skin symptoms, some only show digestive symptoms, and some have both. Our guides to the signs and symptoms of dog food intolerances and allergies and the skin issues caused by food allergies and intolerances go into more detail.
When to see a vet straight away
Contact your vet urgently if your dog has:
- Swelling of the face, lips, eyes or ears
- Hives (raised lumps across the skin)
- Difficulty breathing or collapse
- Repeated vomiting or diarrhoea, or blood in either
- Signs of pain, lethargy or not eating
Persistent itching, broken or infected skin and ongoing ear problems also need a vet's attention, as secondary infections usually need treatment before you can see what's really going on.
What are dogs most commonly allergic to?
Most food allergies in dogs are triggered by proteins, and the most common culprits are the ingredients dogs eat most often. A review of published studies covering 297 dogs with food allergies found these were the most frequently reported triggers:
| Food | Share of dogs reacting |
|---|---|
| Beef | 34% |
| Dairy products | 17% |
| Chicken | 15% |
| Wheat | 13% |
| Soy | 6% |
| Lamb | 5% |
| Corn | 4% |
| Egg | 4% |
| Pork, fish and rice | 2% each |
Some dogs react to more than one food. Chicken is often blamed for allergies, but it's further down the list than beef and dairy. You can read more in Is It True That Most Dogs Are Allergic to Chicken?
Are grains a common cause?
Wheat can trigger allergies, but grains as a whole are much less likely to be the problem than animal proteins. Switching to a grain-free food won't help if your dog is reacting to the beef or chicken in it.
Is it food, or something else?
Itchy skin in dogs has several possible causes, and food allergy is less common than flea allergy or environmental allergy. Many of the symptoms overlap, so it's worth ruling out the other causes with your vet.
| Cause | Clues |
|---|---|
| Flea allergy | Itching focused on the lower back and base of the tail; can be triggered by just a few bites |
| Environmental allergy (pollen, grass, dust mites, moulds) | Often seasonal, worse after walks or at certain times of year; paws, face and belly commonly affected |
| Food allergy | Itching all year round; may come with digestive symptoms; doesn't improve with the seasons |
| Skin infection or mites | Sores, scabs, odour or sudden worsening; needs a vet to diagnose and treat |
A dog can have more than one of these at the same time. If your dog's itching gets worse in spring and summer or after time on the grass, read Can Dogs Be Allergic to Grass?
How food allergies are diagnosed: the elimination diet
The only reliable way to diagnose a food allergy in dogs is an elimination diet followed by a food challenge. It takes time and commitment, but it gives you a clear answer.
1. Talk to your vet first
Your vet can treat any skin or ear infections, check for fleas and other causes of itching, and help you choose the right diet.
2. Choose an elimination diet
Your dog will eat a diet that contains only ingredients they're unlikely to react to. This is usually either:
- A hydrolysed protein diet, where the proteins are broken down into pieces too small for the immune system to recognise, or
- A novel protein diet, using a protein and carbohydrate your dog has never eaten before
Many shop-bought foods labelled "hypoallergenic" or "limited ingredient" can contain traces of other proteins, so vets usually recommend a prescription diet or a carefully planned home-cooked one. Our hypoallergenic dog food buyer's guide explains the options.
3. Feed nothing else for at least 8 weeks
Research shows that more than 90% of dogs with a food allergy improve within 8 weeks on a strict elimination diet, so that's the recommended minimum. During the trial your dog should have no treats, chews, table scraps, flavoured medicines or flavoured toothpaste unless your vet has approved them.
4. Reintroduce the old food (the food challenge)
If your dog's symptoms improve, your vet will ask you to reintroduce their old food. If the symptoms come back, usually within a few days to two weeks, that confirms a food allergy. You can then test individual ingredients one at a time to find the exact triggers.
For a realistic timeline of how quickly symptoms settle, see Dog Food Allergies: How Long to Clear Up?
Can a test diagnose a food allergy?
No. Veterinary research has found that no blood, saliva or hair test can reliably diagnose a food allergy in dogs. Food-specific blood tests give inconsistent results, and other tests aren't recommended for diagnosis. An elimination diet and food challenge remain the only way to confirm it.
That doesn't mean testing has no place, as long as you know what each test is for:
IgE blood testing for environmental allergies
Vets use IgE blood tests to identify environmental allergens, such as pollens, grasses and dust mites, once allergic skin disease has been diagnosed. This helps with avoidance and with choosing allergens for immunotherapy. Our Dog Allergy Test is an IgE blood test you collect at home, with a report you can share with your vet. It's most useful if your dog's itching is seasonal or linked to the outdoors. Treat any food results as a guide only, and confirm them with an elimination diet.
Hair sensitivity tests
Our hair tests, such as the Basic Dog Intolerance Test and the Ultimate Pet Food Sensitivity Test, are non-invasive wellness screens. They don't measure allergies and they can't diagnose a medical condition. Some owners use the results as a starting point when deciding which foods to try removing first. If you do, always confirm any changes with a proper elimination and reintroduction, ideally with your vet's support.
Living with a dog with food allergies
Food allergies can't be cured, but they can be managed well once you know what to avoid.
- Avoid the trigger completely. Even small amounts can cause a flare-up, so check every food, treat and chew.
- Read labels carefully. Ingredients like "animal derivatives" or "meat and animal by-products" can hide proteins your dog reacts to.
- Tell everyone. Make sure family, dog walkers and sitters know not to give extra food or treats.
- Watch for flavoured medicines and supplements. Many contain beef, chicken or pork flavouring.
- Keep an eye out for new reactions. Some dogs develop new allergies over time, so speak to your vet if symptoms return.
- Treat flare-ups early. Your vet can help with itch relief and any skin or ear infections while you get things under control.
Frequently asked questions
Can dogs suddenly develop food allergies?
Yes. Food allergies usually develop to foods a dog has eaten for months or years, so symptoms can appear even though nothing in their diet has changed.
Can puppies have food allergies?
Yes. Food allergies can start at any age, including in puppies under a year old. Itching that carries on all year in a young dog is worth discussing with your vet.
How long does it take for food allergy symptoms to clear up?
Many dogs start to improve within a few weeks of removing the trigger, but it can take up to 8 weeks for symptoms to settle fully. Skin and ear infections may need treating before you see the full improvement.
Is grain-free food better for dogs with allergies?
Not usually. Most food allergies are caused by animal proteins such as beef, dairy and chicken, not grains. Grain-free is only helpful if your dog has been shown to react to a specific grain.
Are food allergies and food intolerances the same thing?
No. A food allergy involves the immune system and often causes itchy skin. A food intolerance doesn't involve the immune system and mainly causes digestive symptoms such as diarrhoea and wind.
Can a blood or hair test diagnose a food allergy in dogs?
No test can reliably diagnose a food allergy. An elimination diet followed by a food challenge is the only way to confirm one. Tests can help guide where to start, but their results should always be checked with a diet trial.
Are some breeds more likely to have food allergies?
Any breed, including crossbreeds, can develop a food allergy. Some breeds are more prone to itchy, allergic skin in general, but that is often caused by environmental allergies rather than food, so it's worth ruling out other causes with your vet.
Sources
- Mueller RS, Olivry T, Prélaud P. Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats. BMC Veterinary Research, 2016.
- Olivry T, Mueller RS, Prélaud P. Critically appraised topic on adverse food reactions of companion animals (1): duration of elimination diets. BMC Veterinary Research, 2015.
- Mueller RS, Olivry T. Critically appraised topic on adverse food reactions of companion animals (4): can we diagnose adverse food reactions in dogs and cats with in vivo or in vitro tests? BMC Veterinary Research, 2017.