Your dog has vomited again. Or it is diarrhoea this time — loose stools, an accident in the house, a mess to clean up. You are wondering whether this could be their food. Is it a food allergy? Something they ate off the street? A sign of something serious? This article helps you think through the possibilities.
Vomiting and diarrhoea in dogs are extremely common. They have many causes, and food is only one of them. This article explains when digestive symptoms might be linked to food allergies or intolerances, what other causes to consider, and how to work with your vet to find out what is going on.
the evidence
What you'll learn: When vomiting and diarrhoea might be caused by food. How to distinguish food allergy from food intolerance in the digestive system. Other common causes of digestive upset in dogs. When to see a vet. How to investigate food as a possible cause.
Vomiting and Diarrhoea Are Common in Dogs but Not Normal to Ignore
Most dogs will vomit or have diarrhoea at some point. Occasional vomiting — particularly if it is just yellow bile or foam and happens once or twice — can be normal. Diarrhoea is also common, especially after a dietary change or eating something they should not have.
What is not normal is persistent vomiting, diarrhoea that lasts more than a day or two, vomiting that happens repeatedly over weeks, or any digestive upset accompanied by weight loss, lethargy, blood in the stool, or a dog that is clearly unwell. These signs warrant a vet visit.
When digestive symptoms are ongoing, food is one of the first things vets consider — because it is common, treatable, and something owners can address at home with the right guidance.
How Food Allergies Cause Digestive Symptoms
A true food allergy involves the immune system. When a dog with a food allergy eats a problem ingredient, their immune system produces antibodies against that food protein. This triggers inflammation in the gut lining and the release of histamine and other inflammatory chemicals. The result can be vomiting, diarrhoea, or both.
With a food allergy, digestive symptoms are often accompanied by skin signs — itching, paw licking, ear infections, red skin. If your dog has digestive symptoms alone with no skin involvement, a food allergy is less likely. Food intolerances, by contrast, affect the digestive system without involving the immune system.
The key distinction: food allergies produce both digestive and immune responses. Food intolerances produce digestive symptoms only.
How Food Intolerances Cause Digestive Symptoms
A food intolerance affects digestion rather than immune function. The dog lacks a particular enzyme needed to break down a food component, or the gut simply reacts poorly to a specific ingredient.
Lactose intolerance is a well-documented food intolerance in dogs and one of the most commonly recognised by owners. A dog without enough lactase enzyme cannot digest lactose, the sugar in milk. This causes wind, bloating, loose stools, and diarrhoea within a few hours of consuming dairy. It is uncomfortable for the dog but is not an immune reaction.
Other intolerances are less well understood. Some dogs react to certain fats, specific proteins, or food additives. These reactions are not allergies — there is no antibody response — but they produce very similar digestive symptoms.
Signs That Your Dog's Digestive Symptoms Might Be Food-Related
The following patterns suggest food as a more likely cause of digestive symptoms:
Symptoms appear shortly after eating. If your dog regularly vomits within 30 minutes to a few hours of a meal, food allergy or intolerance is a strong possibility.
Symptoms happen every time a particular food is eaten. If your dog is fine most of the time but always gets sick after eating chicken-based treats, for example, that food is worth investigating.
Diarrhoea is persistent rather than a one-off. One episode of diarrhoea after eating something unusual is probably not a food allergy. Diarrhoea that persists for days or keeps recurring is worth investigating.
Skin signs are also present. Vomiting or diarrhoea alongside itching, paw licking, or ear infections points toward an allergic basis.
The symptoms are year-round. Food allergies cause symptoms every time the problem food is eaten, so the pattern is consistent year-round. Seasonal digestive symptoms are more likely to have an environmental cause.
Other Causes of Digestive Symptoms to Rule Out First
Before concluding that food is responsible for your dog's digestive symptoms, your vet will want to rule out other causes. These include:
Parasites such as roundworm, hookworm, giardia, and coccidia. A simple stool sample test can identify most parasites. Parasites are a very common cause of diarrhoea in dogs, especially puppies and dogs who spend time outdoors.
Bacterial infections such as Salmonella, Campylobacter, or E. coli. These can cause acute vomiting and diarrhoea and are sometimes linked to contaminated food or water.
Viral infections such as parvovirus, coronavirus, or distemper. These are less common thanks to vaccination but remain serious possibilities in unvaccinated dogs.
Dietary indiscretion — eating something unusual, spoiled, or not meant for dogs. This is probably the most common cause of acute vomiting and diarrhoea in dogs. It is usually self-limiting.
Foreign bodies such as toys, bones, or fabric that the dog has swallowed. These can cause partial or complete obstruction, leading to repeated vomiting, not eating, and abdominal pain.
Stress-related digestive upset. Some dogs react to changes in routine, travel, or new household members with digestive symptoms.
Medical conditions such as pancreatitis, inflammatory bowel disease, liver disease, or thyroid disorders. Your vet will consider these in older dogs or when symptoms are persistent and have no other explanation.
This list is not meant to alarm you. It is meant to show why a vet's involvement is important — many of these conditions look similar to food intolerance but require completely different treatment.
How to Investigate Whether Food Is the Cause
If your vet has ruled out parasites, infections, and other medical conditions, the next step is investigating food as a possible cause. The process is an elimination diet trial — described in detail in our article on The Elimination Diet for Dogs.
The basic process:
Your dog is fed a novel protein source they have never eaten — such as venison, kangaroo, or duck — or a prescription hydrolysed protein diet for 8 to 12 weeks. During this time they eat nothing else.
If symptoms improve during the trial, the diet is the likely cause. One by one, individual ingredients are reintroduced while you monitor for the return of symptoms. The ingredient that triggers symptoms is the culprit.
This process takes time and commitment, but it is the only reliable way to identify a food trigger without guessing.
60-second check
Is your dog's tummy trying to tell you something?
Six quick questions about the pattern. No right answers, just signals.
We'll email you the 8-week elimination diet guide and a printable symptom tracker. No spam, unsubscribe whenever.
Frequently Asked Questions
Can food allergies cause vomiting in dogs?
Yes. A true food allergy involves the immune system and can trigger vomiting alongside other symptoms. However, vomiting on its own — with no skin signs and no clear pattern tied to specific foods — is less likely to be a food allergy. Many other causes of vomiting need to be ruled out first.
My dog has diarrhoea. Could it be their food?
Yes, food is one possible cause of diarrhoea in dogs. The most common causes of acute diarrhoea are dietary indiscretion and parasites. Persistent or recurrent diarrhoea that has been investigated by your vet may be linked to food allergies or intolerances.
What foods most commonly cause digestive symptoms in dogs?
Beef, chicken, dairy, and egg are the most common food allergens in dogs and can all cause digestive symptoms. Soy and wheat can also trigger reactions in some dogs. The only way to know which food is responsible is through an elimination diet trial.
Should I change my dog's food if they have vomiting or diarrhoea?
Do not change the diet without understanding the cause. Switching foods randomly can make it harder to identify the problem. Speak to your vet first — they may recommend a temporary bland diet or a specific elimination diet, depending on what they suspect.
How do I know if my dog has a food intolerance rather than a food allergy?
A food intolerance produces digestive symptoms without an immune system response. There is no itching or skin involvement. A food allergy typically also causes skin signs. Your vet can help you distinguish between the two through the elimination diet process and by ruling out other conditions.
When should I take my dog to the vet for vomiting or diarrhoea?
Take your dog to the vet if they have vomiting or diarrhoea that lasts more than 24 hours, if they are visibly unwell or in pain, if there is blood in the stool or vomit, if they are not eating or drinking, if they are losing weight, or if they have a fever. Puppies, senior dogs, and dogs with other health conditions should be seen promptly.
the short version
- Vomiting and diarrhoea have many causes — food is one possibility, not the only one
- Food allergies affecting the gut often also cause skin signs; food intolerances typically cause digestive symptoms only
- Parasites, bacterial infections, and dietary indiscretion are more common causes of digestive upset than food allergies
- A persistent pattern — symptoms that keep returning or never fully resolve — is more suggestive of a food cause than a single episode
- The only reliable way to identify a specific food trigger is an 8-to-12-week elimination diet trial under veterinary supervision
- See your vet promptly if symptoms are severe, persistent, or accompanied by lethargy, blood, or weight loss
the evidence
This article is here to help you understand what your vet has told you. It is not a substitute for professional veterinary advice. If your dog has persistent vomiting or diarrhoea, please speak to your vet.
Last updated: April 2026
the food behind the guide
One novel protein.
None of the usual suspects.
Some Grub is a cold-pressed, hypoallergenic dog food built around insect protein — a protein most dogs have never met, which is the whole point of a food trial.
See the food →
