Nutritional management of food allergy in dogs

Food allergy (food hypersensitivity) is widely recognised in dogs, and results in clinical signs affecting the skin, gastrointestinal tract, or both. Food allergy is reported to be responsible for to up to 20-25% of cases of non-seasonal allergic dermatoses, and for many cases of gastroenteritis.

Food allergy is caused by an immunologically mediated hypersensitivity reaction:

• Most cases are thought to be type I (immediate) hypersensitivity reactions, mediated by immunoglobulin E (IgE).
• Both types III and IV hypersensitivity may also be involved in some cases.

The diagnosis and management of food allergies relies on:

• Identifying the offending allergens through dietary trials using a "hypoallergenic diet".
• Subsequently avoiding the identified allergens.

Food allergens are almost exclusively proteins or glycoproteins, but the size and structure of the protein helps determine its ability to induce hypersensitivity:

• Most allergens have a molecular weight above 20000 Daltons - large enough to have sufficient complexity to interact with antibodies or T-cell receptors.
• Proteins also have to be small enough to pass through the mucosal barrier and are usually less than 70 000-80 000 Daltons.

Extreme hydrolysis of proteins in hypoallergenic diet is not necessary as it might contribute to the osmotic diarrhoea risk.

THE VALUE OF HYDROLYSED DIETARY PROTEINS

The best approach to the diagnosis of canine food allergy is to use a food where the potential allergens have been broken down and denatured to render them harmless and non-immunologically reactive by hydrolysis. A good hydrolysed protein diet is the most reliable way of diagnosing food allergy, and it is essential for an effective food trial that the diet used is fed exclusively. To facilitate this, a diet with excellent palatability is required.

Non-modified soya protein has a molecular weight of around 29 000 Daltons, but the modified, fractionated soya protein in Canine HA, as well as the diet itself has molecular weights that fall well below the 18 000 to 36 000 Daltons range of typical food allergens.

Dogs that may benefit from a trial with a true hypoallergenic diet include:

• Dogs with cutaneous or gastrointestinal signs potentially associated with food allergy (including inflammatory bowel disease).
• Atopic patients – a food trial may be appropriate as many dogs have multiple allergies and may respond to a food trial.

CLINICAL ADVANTAGES WITH THE USE OF CANINE HA

Canine HA provides:

• A single protein source hydrolysed to low molecular weights –hydrolysing proteins to less than 18000 Daltons helps render them immunologically inert, and alters their structure to further reduce antigenicity.
• An exceptional digestibility of all ingredients to reduce the antigenic load and help manage any GI signs.
• Purified starch source and sucrose, from which virtually all intact protein has been removed. This dramatically reduces the risk of allergic responses.
• Long-chain omega-3 fatty acids to help reduce inflammatory responses. These are incorporated into cell membranes in place of a proportion of arachidonic acid, Long-chain omega-3 fatty acids subsequently compete with arachidonic acid as a substrate for eicosanoid production and thereby maximise the natural anti-inflammatory process.