What is the Difference Between Food Allergies and Adverse Reactions to Food in Dogs?

What is the Difference Between Food Allergies and Adverse Reactions to Food in Dogs?

The main difference between food allergies and adverse reactions to food in dogs lies in the immune system's involvement. Food allergies are caused by an overreaction of the immune system to certain proteins, requiring repeated exposures before symptoms occur. Adverse food reactions, including intolerances, typically do not involve the immune system and can happen on the first exposure to a problematic food. While symptoms may look similar, understanding the distinction is crucial for identifying the right treatment.

Why Do Dogs Experience Food Allergies or Adverse Reactions?

Food Allergies: An Immune System Overreaction

Food allergies in dogs occur when the immune system mistakenly identifies a protein in food as harmful. This triggers the release of histamines, leading to symptoms such as:

  • Itchy skin or chronic ear infections
  • Gastrointestinal issues like vomiting or diarrhoea
  • Red, inflamed skin or hives

These reactions often develop after several exposures to the offending food.

Food Intolerances: Non-Immune Responses

Food intolerances, on the other hand, involve the digestive system. A dog might lack the enzymes needed to process a specific food, or the food may irritate the gut. Common examples include:

  • Lactose intolerance causing bloating and diarrhoea
  • Sensitivity to high-fat foods leading to vomiting or upset stomach

Because food intolerances don't involve the immune system, they can happen after a single exposure.

What Types of Adverse Food Reactions Can Dogs Have?

1. Food Poisoning

Food poisoning occurs when a dog eats something toxic or spoiled, leading to sudden gastrointestinal distress. Common causes include:

  • Overeating certain nutrients like vitamin A or D
  • Scavenging spoiled food or garbage
  • Consuming toxic foods (e.g., chocolate, grapes, onions)

2. Reactions to Food Additives

Though rare in dogs, additives like preservatives or artificial flavours might cause adverse reactions. A known risk is disulfide in onions, which can harm red blood cells.

3. Drug-Like Reactions

Some foods contain natural compounds that mimic drug effects. For example, histamine in certain foods can cause nausea, diarrhoea, and facial swelling in rare cases.

4. Carbohydrate Intolerance

While uncommon, carbohydrate intolerance, such as lactose intolerance, can lead to symptoms like diarrhoea or abdominal discomfort after consuming dairy products.

5. Dietary Indiscretion

Dogs are notorious for eating things they shouldn't—whether it's spoiled food, non-food items, or greasy leftovers. This can result in:

  • Gastrointestinal distress from bacteria, fat, or grease
  • Physical blockages or injuries from ingested objects like bones or plastic

How to Identify Whether It’s a Food Allergy or Intolerance

Symptoms to Watch For

Both food allergies and intolerances can cause:

  • Vomiting and diarrhoea
  • Excessive scratching or licking
  • Changes in stool quality or frequency

Key Differences

  • Food allergies are often accompanied by skin problems, such as redness or rashes.
  • Food intolerances tend to cause digestive symptoms without skin issues.

Monitoring Your Dog’s Diet

Keeping a detailed food diary, including ingredients, portion sizes, and timing of symptoms, can help your vet pinpoint the issue.

What Should You Do if Your Dog Has an Adverse Reaction?

Immediate Actions

  • Stop feeding the suspected food: Remove the item from your dog’s diet immediately.
  • Provide hydration: Ensure your dog has plenty of fresh water to counteract dehydration from vomiting or diarrhoea.
  • Monitor closely: Track any changes in symptoms over the next 24–48 hours.

Seeking Veterinary Care

If symptoms persist or worsen, consult your vet. Severe reactions, such as difficulty breathing or extreme lethargy, require emergency attention.

Preventing Future Food Reactions in Dogs

Elimination Diets

Work with your vet to identify problem ingredients by feeding your dog a simple diet of novel proteins and carbohydrates, gradually reintroducing foods to identify triggers.

Choose Limited-Ingredient Dog Foods

Opt for high-quality, limited-ingredient dog foods free from common allergens like beef, chicken, dairy, and wheat.

Be Cautious with Treats and Table Scraps

Even small amounts of human food or treats can trigger reactions. Stick to treats made from safe, simple ingredients.

When to See a Vet

You should consult a vet if:

  • Symptoms persist for more than a few days.
  • Your dog experiences severe itching, swelling, or gastrointestinal distress.
  • You suspect an underlying food allergy or sensitivity.

Your vet might recommend diagnostic tests like blood panels, skin tests, or specialised elimination diets.

Conclusion: Know the Difference to Help Your Dog Thrive

Understanding whether your dog is dealing with a food allergy or intolerance is key to effective management. Both conditions can affect your dog’s quality of life, but with careful observation and a vet’s guidance, you can pinpoint the issue and take action.

If you're concerned about your dog’s symptoms, try My Pet Sensitivity's food allergy test to uncover potential triggers and find the best dietary solutions for your furry friend.

To provide you with technically accurate evidence-based information, content on the MyPetHealthStore blog is reviewed by medical professionals with veterinary expertise.

This article was reviewed by:

Hannah Shepherd RVN
Qualified Registered Veterinary Nurse & BVNA Member