What to do if your dog has a food allergy

Persistent itchy skin or long-running digestive trouble in dogs is one of the most common challenges in everyday veterinary practice. Food allergy is a significant cause of these complaints, although statistically it is diagnosed less often than atopic dermatitis or flea allergy dermatitis. Diagnosing and treating it demands a great deal of discipline from the owner and a strict approach to feeding, which is often the hardest part of the journey back to a comfortable life for the animal.

Food allergy vs food intolerance: the key differences

In everyday speech the two terms are often used interchangeably, but medically they describe two entirely different pathological processes. Understanding the difference is fundamental to getting the treatment right.

A food allergy in dogs is an inappropriate, exaggerated immune response to a specific protein taken in with food. The body treats a harmless dietary component as an enemy and sets off an inflammatory cascade that leads to antibody production. The hallmark of a true allergy is that even a trace amount of the offending protein can trigger intense, widespread itching over the whole body.

Food intolerance, by contrast, usually stems from a lack or shortage of the digestive enzymes needed to break down a particular ingredient. The immune system is not involved, and the problem shows up directly in the digestive tract. Importantly, the severity of intolerance symptoms is usually closely tied to how much of the problem food was eaten. A small amount may cause no reaction at all, whereas a larger portion leads to painful bloating, gurgling in the gut and acute diarrhoea.

What are the symptoms of food allergy in dogs?

The range of symptoms caused by food allergens is remarkably wide. The clinical picture varies a great deal from one patient to the next, and individual signs frequently overlap and occur together. Broadly, they fall into three main categories.

Skin symptoms

Skin changes are the most common reason for a visit to the vet. The main sign is persistent itching that is hard to control. The dog scratches, licks and chews at its coat intensely, damaging the skin in the process. The itching is usually concentrated around the muzzle, between the toes, in the groin, on the belly and around the anus.

The skin shows marked redness, known as erythema. A skin barrier damaged by scratching is an open door for secondary infections. Bacteria and yeasts very often multiply, producing painful, pus-filled patches of skin inflammation commonly called hot spots. Increased flaking, crusting and extensive hair loss also appear.

Recurrent ear infections

Inflammation of the external ear canal is another classic sign of food-related allergy. It is worth stressing that chronic, hard-to-treat ear problems are quite often the only visible symptom of the disease in a given patient.

The ear flaps become intensely red and swollen. The animal is very uncomfortable, constantly scratches around its head and shakes it in a characteristic way. Excess wax of an altered colour builds up in the ear canal, with a distinctly unpleasant, sweetish smell that usually points to a concurrent yeast infection.

Digestive symptoms

Although skin symptoms take centre stage, gastrointestinal complaints affect a sizeable proportion of allergic dogs. These are chiefly chronic or recurrent loose stools and more frequent bowel movements, often more than three times a day. Some dogs also show regular vomiting, excessive wind and a noticeable loss of weight despite a normal appetite.

What are dogs most often allergic to?

Identifying the trigger of an allergic reaction is a difficult and time-consuming task. Veterinary statistics clearly show that animal proteins are responsible for the vast majority of cases. The ingredients that most often cause adverse reactions are:

• beef,
• poultry,
• dairy,
• lamb,
• wheat,
• soya,
• maize.

Matters are further complicated by the fact that many patients are sensitive to several ingredients at once. That is why cutting out just one suspect protein source rarely brings the lasting results owners hope for.

Diagnosis: the gold standard is an elimination diet

Modern veterinary medicine has no reliable blood tests that can definitively confirm a food allergy and pinpoint the offending ingredient without error. The only fully effective and dermatologically recognised diagnostic method is a strictly conducted elimination diet.

How an elimination diet works

The key to success is a radical switch to a protein source the animal’s body has never encountered before. This means introducing a novel, rarely used meat such as venison, horse, ostrich or insect protein. Another option is a specialist food based on hydrolysed protein, which is discussed later in this article.

For an elimination diet to have any diagnostic value, it must be followed for an absolute minimum of eight to twelve weeks. Throughout that time the dog may be given only the chosen food and water. Feeding any treats, table scraps or chews of unknown origin is strictly off limits. Even the smallest slip, such as a single piece of sausage, wipes out weeks of effort and means starting the whole process again from scratch.

Food challenge

If the skin and digestive symptoms settle completely during the elimination diet, the most important diagnostic step follows: the challenge. This involves deliberately returning to the original diet suspected of containing the allergens.

The reintroduced ingredient is usually fed for around fourteen days while the animal is watched closely. If the itching, ear problems or diarrhoea flare up again during that time, the diagnosis of food allergy is confirmed once and for all. The patient then goes straight back onto the proven hypoallergenic diet to calm the inflammation down again.

What should you feed an allergic dog?

Choosing the right food for a dog with a confirmed allergy is essential to keeping it healthy and comfortable in the long term. There are several proven options on the market that allow meals to be balanced safely.

Hypoallergenic dog food with hydrolysed protein

The gold standard for managing allergic dogs is a specialist hypoallergenic food based on hydrolysis. Hydrolysed protein undergoes a technological process that breaks it down into fragments called peptides, which are so small that the immune system can no longer recognise them and does not mount an allergic response. These veterinary diets are highly safe and guarantee a complete balance of nutrients. They are an excellent choice for running an elimination diet and work well as a long-term diet for highly sensitive patients.

Single-protein diets

An alternative to hydrolysed diets is single-protein food built around one animal protein source that is new to the dog. These products are available without a veterinary prescription, but choosing one calls for a very careful look at the ingredients list. Make sure the manufacturer guarantees no cross-contamination during production, a frequent problem with cheaper commercial foods.

Home-cooked meals

Many owners choose to prepare their dog’s meals themselves. This gives full control over every single ingredient that ends up in the bowl. Bear in mind, however, that a home-made meat diet is very rarely balanced in terms of vitamins, minerals and fatty acids. Feeding nothing but cooked meat with a filler for a long period leads to dangerous deficiencies, so a home-made menu must be agreed with a veterinary nutritionist and topped up with suitable supplements. To meet this need, professional dog catering companies have appeared on the market, delivering balanced, cooked meals made from carefully selected ingredients.