PetsCareLab

Adverse food reaction (AFR) in dogs refers to an unusual and harmful response to ingredients in what is typically considered “normal” dog food.

There are two primary types of AFR affecting dogs: food allergies, which involve the immune system mistakenly reacting to certain ingredients, and food intolerances, which cause adverse effects without involving the immune system.

Although these conditions have different underlying causes, they often present with similar symptoms and are diagnosed through comparable methods. Treatment usually involves dietary modifications, such as switching to a hydrolyzed protein diet designed to minimize immune reactions.

What Are Food Allergies in Dogs?

Food allergies in dogs occur when their immune system reacts aggressively to specific food ingredients—most commonly proteins such as chicken, beef, or dairy. Unlike sudden allergic reactions, these immune responses tend to develop gradually over time.

When a dog allergic to a certain protein consumes it, their immune system identifies it as a threat and mounts a defensive attack. This immune response often manifests as skin issues, including persistent itching, redness, and swelling. Sometimes, gastrointestinal symptoms like vomiting, diarrhea, or increased gas also occur.

It’s important to note that food allergies are relatively rare compared to other types of allergies dogs may experience, such as seasonal or flea-related allergies. In fact, only about 0.2% of dogs suffer from true food allergies.

What Is Food Intolerance in Dogs?

Food intolerance differs from allergies in that it does not involve the immune system. It can appear either immediately upon first exposure to a particular ingredient or develop gradually over time.

In food intolerance cases, the problematic component may be a protein or another food substance. Lactose intolerance in humans is a familiar example. Unlike allergies, dogs with food intolerance may tolerate small quantities of the offending ingredient without severe reactions, whereas even trace amounts can trigger symptoms in allergic dogs.

Symptoms of Food Intolerance and Food Allergies in Dogs

The symptoms of food allergies and food intolerances in dogs often overlap and can include:

• Skin-related symptoms (common to both allergies and intolerance):
  • Persistent itching and red skin
  • Recurrent ear and skin infections
  • Noticeable hair loss
  • Frequent licking or chewing of the feet (brown staining on paw undersides is a common clue to vets)
• Gastrointestinal symptoms (common to both allergies and intolerance):
  • Diarrhea
  • Vomiting
  • Excessive flatulence (gas)
  • Weight loss
  • Reduced energy levels and lethargy
• Anaphylaxis (a rare but serious symptom related to food allergies only):
  • Hives and swelling around the face

Causes of Food Allergies and Food Intolerance in Dogs

There may be hereditary components influencing the development of food allergies and intolerances in dogs, though the precise reasons why some dogs develop these reactions while others don’t remain unclear.

Dogs can be affected at any stage of life, whether young or older. Though any breed can develop these conditions, certain breeds—like Labrador Retrievers, West Highland White Terriers, and Cocker Spaniels—seem to be more prone.

Common allergens and intolerance triggers mostly involve proteins, including:

• Chicken
• Beef
• Dairy
• Wheat
• Soy
• Eggs

How Veterinarians Diagnose Food Allergies and Food Intolerance in Dogs

Unfortunately, there’s no definitive blood or skin test to diagnose food allergies in dogs. Many available tests lack accuracy. Instead, veterinarians rely on a thorough physical examination, observation of symptoms, and most importantly, a carefully managed food trial.

A food trial typically spans eight to twelve weeks. During this time, it is crucial to feed the dog only the prescribed food—no treats, snacks, or alternative diets—to ensure reliable results.

Because some heartworm and flea/tick preventatives contain proteins like chicken or beef, it’s important to discuss suitable options with your vet to avoid confounding the trial.

There are several approaches to food trials:

• Prescription hydrolyzed protein diets: These diets break proteins into tiny particles too small to trigger immune responses.
• Novel protein and carbohydrate diets: These contain unusual ingredients not typically found in standard dog foods, limiting exposure to common allergens.
• Skin support diets: Fortified with bioactive compounds and phytonutrients to help reduce immune system overactivity.

While diagnostic tests exist, food trials remain the gold standard for accurately identifying food allergies and intolerances in dogs.

Treatment of Food Allergies and Food Intolerance in Dogs

With the right dietary adjustments, most cases of food allergies and intolerance in dogs can be successfully managed.

Best Diets for Dogs With Food Allergies

There’s no “one-size-fits-all” solution since allergies are specific to each dog. The ideal diet contains ingredients your dog is not allergic to, while providing balanced nutrition.

Therapeutic diets—available through veterinary prescription—are often necessary to ensure ingredient novelty and avoid cross-contamination. Even small traces of allergens can provoke symptoms, so strict adherence is crucial.

PetsCareLab offers veterinary diets specially designed to manage food allergies, including:

• PetsCareLab Hydrolyzed Salmon Diet: Featuring hydrolyzed salmon protein broken down to avoid immune detection, this diet is gentle on sensitive immune systems.
• PetsCareLab Novel Protein Alligator Diet: Utilizing alligator protein, an uncommon ingredient, providing an excellent option for dogs allergic to common protein sources like poultry or beef.

Best Diets for Dogs With Food Intolerance

Because food intolerances lack an immune system component, managing them often involves feeding a limited-ingredient, non-prescription diet that simplifies the protein and carbohydrate sources.

Examples from PetsCareLab’s limited-ingredient line include:

• PetsCareLab Skin and Stomach Care Salmon and Potato: Single-protein formula using deboned salmon, free from poultry, corn, wheat, soy, and artificial additives—perfect for sensitive dogs.
• PetsCareLab Skin and Stomach Care Duck and Potato: Grain-free, gluten-free, single-protein option designed for dogs needing to avoid common grains.
• PetsCareLab True Solutions Perfect Skin and Coat: A single-protein diet clinically shown to promote healthy skin and shiny coat, with real salmon as the main ingredient.

Allergy Medications

Dogs with food allergies frequently also suffer from environmental allergies. In many cases, veterinarians prescribe medications such as Apoquel, Cytopoint, antihistamines, or steroids to alleviate symptoms alongside dietary therapy.

Supplements rich in omega fatty acids can also support skin health by strengthening the skin’s natural barrier. Popular options include:

• Nutramax Welactin
• Dechra EicosaDerm

Recovery and Long-Term Management of Food Intolerance and Food Allergies in Dogs

While food allergies and intolerances cannot be cured, they can be effectively controlled through ongoing dietary management and strict avoidance of trigger ingredients.

Compliance with your veterinarian’s guidance on diets and treats is essential to prevent flare-ups.

If your dog is undergoing a food trial, improvements may become noticeable within four weeks as licking and chewing lessens, though full symptom resolution might take up to 12 weeks.

What is the most common food allergy in dogs?

Protein sources like beef and chicken are the most frequent causes of food allergies in dogs.

What are the most common signs of food allergies in a dog?

Typical signs include itching, recurrent skin and ear infections, and constant licking or chewing of the feet. Keep in mind that other skin conditions can show similar symptoms.

Can you test a dog for food allergies?

Food allergies in dogs are primarily diagnosed through structured food trials under veterinary supervision. Blood and skin tests are available for environmental allergies but are unreliable for food allergies.

Can you cure a food allergy in a dog?

Food allergies are lifelong conditions without a cure; however, they can be managed effectively by avoiding allergenic foods and following a proper diet.

How long does it take dog allergies to clear up?

Once the offending ingredient is identified through a food trial—which can take up to 12 weeks—symptoms may improve over time. If secondary infections have developed, those will require separate treatment.

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

Food allergies trigger an immune system reaction, while food intolerances do not involve the immune response.

What causes food intolerance?

Food intolerance is a type of adverse food reaction wherein the dog’s body cannot properly process or tolerate certain ingredients, causing symptoms similar to allergies but without immune involvement.