As a breeder, knowing the role food allergy plays in chronic issues like itching, diarrhoea, and vomiting can make a difference in the comfort and health of your dogs, and knowing what might be heritable may affect your breeding decisions. Whether you're a new breeder or have years of experience, understanding the basics of food allergy — how to identify, test for, and manage it —equips you to make informed care and breeding decisions, and support puppy owners in better caring for their new companions. 

Food Allergy vs. Food Intolerance

Food allergy and intolerance are key causes to consider when dogs experience chronic itching, vomiting, or diarrhoea, but it’s essential to understand the difference between the two. A food allergy occurs when a dog’s immune system encounters a specific food ingredient — usually a protein or complex carbohydrate — and overreacts to it, generating antibodies against the protein with repeated exposure. Dogs can potentially have allergic reactions to any food ingredient, but beef, dairy, wheat gluten, egg, or chicken are some of the most common. Unlike food intolerances, which typically only cause gastrointestinal (GI) signs and can be seen with first exposure, food allergies develop with repeated exposure to the allergen and can lead to widespread inflammation and subsequent problems with both the digestive system and the skin, including redness and itching. 

In contrast, a food intolerance doesn’t involve the immune system and usually results in GI problems alone, such as diarrhoea, vomiting, or gas. Examples of food intolerance include sensitivities to ingredients like lactose or additives such as preservatives or dyes. 

How Does a Food Allergy Develop? 

In the normal canine digestive system, cells in the gut, called dendritic cells, constantly assess their environment, identifying potential dangers. When a dendritic cell encounters a protein the body has deemed a threat such as a food allergen, it processes that protein into smaller pieces, which triggers an immune response in the local lymph nodes. In dogs with a food allergy, this response is an allergic reaction that leads to the production of IgE antibodies. These antibodies, in turn, cause cells to release compounds such as histamine that result in itching, swelling, and GI discomfort. Typically, the dog will start reacting after repeated exposure to the food allergen, and their reaction to that allergen becomes more significant. 

Signs and Symptoms of Food Allergies in Dogs 

Signs of food allergy can be non-specific and overlap with those caused by food intolerance or atopic dermatitis, a condition where dogs react to environmental allergens like pollen or dust mites.  

Common Signs of Food Allergy Include: 

• Skin Reactions: Itching and scratching, red or inflamed skin, hot spots (moist, irritated skin from licking), hair loss, dry or flaky skin, excessive licking of paws or mouth. 
• Ear Infections: opportunistic bacteria or yeast infections, often with itching or odour, and frequent head shaking due to discomfort. 
• Gastrointestinal Disturbances: Vomiting, diarrhoea, gas, or bloating. 
• Behavioural Changes: anxiety or restlessness due to discomfort, or lethargy. 

Diagnosis and Genetic Testing for Food Allergy 

At present, the most reliable way to test for food allergy in dogs is an elimination diet trial. This involves feeding the dog a diet with limited ingredients—typically novel proteins and carbohydrates the dog hasn’t been exposed to before, or a hydrolysed diet, in which proteins are broken down to reduce immune reactions. This elimination diet is to be followed exclusively for 8–12 weeks, avoiding any other foods, treats, or medications with flavourings. If signs improve, individual ingredients from the original diet are gradually reintroduced to identify the specific food allergens at fault. Although other allergy tests, such as blood-based antibody or skin tests, are sometimes marketed for diagnosing food allergy in dogs, they lack consistency and reliability in scientific studies. The elimination diet trial remains the gold standard. 

No genetic testing for food allergy is currently available and genetic research into food allergy predisposition in dogs is ongoing. However, several breeds show a higher prevalence of food allergy, suggesting a genetic predisposition exists. Genetic factors may influence immune function, skin barrier integrity, and gut health—each playing a role in how a dog’s body recognises allergens. Certain genes are known to contribute to immune response, particularly those in the dog leukocyte antigen (DLA) region, and although not fully understood, plays a part in immune recognition of self and non-self, antibody production and white blood cell responses. Immune dysfunction contributes to allergic responses, cancer, infection and even autoimmune disease, and is therefore one of the primary targets of genetic research. 

What Is the Root Cause of Food Allergy?

The answer to what causes food allergy is likely complex, including the diet ingredients and processing, environment, and the many aspects of the dog itself. While research into the genetics of food allergies in dogs is ongoing, some breeds show a higher prevalence of food allergy, suggesting a genetic predisposition. Many researchers suspect the skin barrier and gut microbiome may also affect development of food allergy by “priming” the immune system to overreact and increasing overall levels of inflammation. A weaker skin barrier, for instance, can allow allergens to penetrate more easily, potentially increasing risk of atopic dermatitis. The gut microbiome, which helps regulate immune response and tolerance to foods, may also impact the likelihood of food allergy.  

Increasingly, scientists consider food allergy to be part of a larger syndrome of conditions related to immune dysregulation, along with atopic dermatitis and GI dysbiosis. Dysbiosis, or a microbial imbalance, is often present in dogs with food allergy, and many dogs with atopic dermatitis often partially improve on a limited ingredient or hydrolysed diet. It is hotly debated whether the GI dysbiosis, weak skin barrier, or food allergy is the first cause, and co-occurrence of these three conditions is a subject of interest in the human field as well, as a similar phenomenon is seen there. 

What Breeders Need to Know: The Impact of Dam and Puppy Diet on Food Allergy 

In humans, research shows that early exposure to specific foods, like peanuts, can build tolerance and reduce allergy risk. This concept of “oral tolerance” suggests that early exposure to particular proteins can train the immune system to recognise these proteins as safe. Some breeders and veterinarians believe a balanced, varied diet for the dam and puppies may support immune tolerance in dogs, although more research is needed to confirm this. 

As discussed previously, the gut microbiome plays a significant role in immune health in dogs. A varied diet can support a diverse microbiome, helping to regulate immune response and tolerance to food proteins. Studies in dogs show that diet can affect gut bacteria composition; for example, raw-fed dogs have greater bacterial diversity compared to those on commercial diets, although they may also carry a higher risk of certain pathogens. In humans, mothers who consume a diet rich in beneficial bacteria, such as in fermented foods, seem to pass on a more diverse gut microbiome to their children, which can positively influence allergy risk. 

While the research is still ongoing, a varied and balanced diet for both dam and puppies may have long-term benefits for immune health and food tolerance. By focusing on a nutritionally rich and diverse diet, breeders can potentially help set puppies up for a healthier immune response, making allergy management easier for future owners. 

References:

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