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Vet-Lexicon

Food allergy and exclusion diet

Currently, there are not any comprehensive figures on how many dogs and cats suffer from food allergies. There is less data available in veterinary medicine than in human medicine, but the number of animals suffering from food allergies appears to have increased over the last few decades. 
The terms allergy and intolerance are often used interchangeably but they are not actually the same. An allergy is a reaction by the body’s own defence system (the immune system). The body overreacts to a harmless foreign substance, known as an allergen, such as a food component, and forms antibodies in response. This is referred to as an immunological reaction. With intolerance, the body’s own defence system is not involved and there is therefore no immunological reaction. In the case of intolerance, other reactions in the body mean that the dog cannot tolerate a certain substance. For example, the body may lack substances (enzymes) to break down or absorb certain components of food, such as lactose, into the body. Whether it is an allergy or an intolerance does not really matter for the dog or the owner, as the symptoms and therefore treatment are similar.
Symptoms of food allergies or intolerances can appear through two organ systems: the skin and the gastrointestinal tract. Either both organ systems can be affected or just one of them. The severity can also vary from mild to severe.

Skin symptoms: 
  • Itching 
  • Skin redness, skin rash 
  • Skin inflammations 
  • Hair loss 
  • Ear infections 
  • Licking and/or biting paws 
  • Redness and inflammation around the eyes 
  • Scabs or thicker skin 

Gastrointestinal symptoms: 
  • Vomiting 
  • Diarrhoea 
  • Bloating 
  • Abdominal pain 
  • Loss of appetite 
  • Weight loss

Causes of allergies 

Whether an animal develops an allergy depends on many different factors. The exact causes of allergies have not yet been conclusively researched and are the subject of numerous studies in human and veterinary medicine. A combination of genetic, environmental and lifestyle factors is considered a possible trigger. Breed can play a role here, with Labradors and Golden Retrievers, West Highland White Terriers or French Bulldogs, for example, being more likely to develop an allergy. The risk of allergies also increases, for example, if you live in an urban environment. The diet during puppyhood can also play a role.

Diagnosing a food allergy 

Unfortunately, the allergy blood tests available at the moment are not very conclusive and are therefore not recommended for diagnosing/ruling out a food allergy. 
A thorough examination of the case is necessary to diagnose a food allergy and rule out any other causes that might trigger similar symptoms. The gold standard for determining/ruling out a food allergy is what is known as the elimination diet (often also called exclusion diet). This requires close co-operation between the vet, dog owner and sometimes a nutritionist to ensure that the diet is followed correctly.
During an elimination diet, the diet is deliberately kept very simple and the classic main allergens such as chicken, beef, dairy products, soya and egg are avoided. There are various feeding options available to carry out an elimination diet: 

1. Home-cooked ration consisting of one protein and one carbohydrate source that the animal has never eaten before 

2. Commercial food consisting of one protein and one carbohydrate source that the animal has never eaten before. This method is possible with our Terra Canis hypoallergenic menus: hypoallergenic dog food – particularly suitable for intolerances 

3. Commercial food with hydrolysed proteins

The selected food is fed for at least 6 to 8 weeks without any additives (no oil, no supplements, nothing from the table etc.). Ideally, no treats should be given during this time. If treats cannot be avoided, the treats should consist of pure meat and always contain the same type of meat as the basic food.  
During the diet, the dog’s state of health is closely monitored and ideally documented. If the symptoms subside, this may already indicate a food allergy. 
After the 6 to 8 weeks are up and the symptoms have subsided, a so-called “rechallenge” can be carried out in which the previously fed food is served. Food allergy sufferers usually react within a very short period of time with a return of the symptoms, which confirms the food allergy diagnosis.

Treating a food allergy

The primary method for treating food allergies in dogs focuses on eliminating the allergenic elements from the food. As soon as the food allergy diagnosis is confirmed, feed the food that was well tolerated during the elimination diet and build on this. You can gradually add new components (e.g. favourite treats, supplements or even a new complete feed if the dog is picky) and then wait 1 or 2 days to see if the old symptoms return. It is important never to add more than one component so that if the symptoms reappear, it can be quickly determined which component was the cause. If no symptoms appear after feeding a new component, it is highly likely that the tested component is well tolerated and can be included in the feeding plan. As a rule, dogs with food allergies do not have very varied feeding plans in order to minimise the likelihood of a reaction to one food component. This is not detrimental as long as all the nutrients are covered.

Author

Dr Martin Bucksch is a veterinarian, author and proud dog owner. Since 2011, he has supported Terra Canis as a consultant, product developer and medical advisor. Dr Bucksch completed his studies in veterinary medicine with distinction in Italy in 1992.