Vet360 Vol 4 Issue 3 June 2017 Vet360 - Page 25

NUTRITION Skin Diseases Which Respond to Nutritional Changes The exact etiology in most clinical cases is not well understood. Food allergy is defined as an immunologically based reaction to food. Immunologic mechanisms of types I-IV have been hypothesised. By Stephen D. White, DVM, DACVD CVC IN SAN DIEGO PROCEEDINGS FOOD ALLERGY Aetiology The exact etiology in most clinical cases is not well understood. Food allergy is defined as an immuno- logically based reaction to food. Immunologic mech- anisms of types I-IV have been hypothesized. A recent report measured cell-mediated immunity (via lymphocyte blastogenesis against food allergens) in both proven food allergic dogs and healthy dogs. The significant- ly higher responses of the food allergic dogs to the foods they were allergic to lends some credence to the role of cell-mediated immunity in this disease 1 . On the other hand, another recent report found that in 10 dogs allergic to either beef, cow’s milk, or lamb, all the dogs had specific IgE antibodies against bovine IgG, (There may be some evidence that this reaction could be due to foetal calf serum used in the vaccines – although this needs to be investigated further). 3 In further contrast, food intolerance is a general term describing any adverse reaction to food that does not have an immunologic basis, including food poison- ing (caused by the direct action of a toxin). From a practical basis, the mech anism of action does not impact the clinician faced with a potential case of chronic food-caused cutaneous disease. It is theorized that most food allergens are proteins. Signalment No sex predilection has been reported for food allergy in dogs or cats. In some studies, no breed predilection was noted. In contrast, two studies found that certain dog breeds may have a risk for the development of food allergy: Soft-Coated Wheaton Terrier, Dalmatian, West-Highland White Terrier, Collie, Chinese Shar Pei, Llasa Apsa, Cocker Spaniel, Springer Spaniel, Minia- ture Schnauzer, Labrador Retriever, Dachshund and the Boxer. Breed data from Colorado State University shows that retrievers may be at greater risk to develop food allergy than other breeds of dogs. While the age at presentation has been reported as variable, several researchers now feel that at least 33% of their cases in dogs are of animals less than 1 year of age 4 . Clearly, while food allergy may occur at any time in animal’s life, it should always be considered as a differential of pruritus in the young dog. History and Clinical Signs The most common clinical sign of food allergy is non-seasonal pruritus which is usually generalised. Pruritus may also be primarily directed at the feet or ears. Very rarely, food allergic dogs with skin lesions but without pruritus have been reported. The most common primary dermatologic lesions are papules and erythema; common secondary lesions are ep- idermal collarettes (usually indicating a pyoderma) pyotraumatic dermatitis (‘hot spots’) hyperpigmen- tation, and seborrhoea. Clinical signs of food allergy have been reported in Cocker Spaniels identical to the idiopathic seborrhoea associated with that breed. Food allergy as the underlying cause of idiopathic onychodystrophy (misshapen, splitting claws [nails]) has been reported in 2 dogs. Food allergy in cats may present as pruritus of the head and face, milliary dermatitis, or one of the mani- festations of the eosinophilic granuloma complex. Reported concurrent gastrointestinal (GI) signs among dogs with cutaneous signs of food allergy are rare; it Issue 03 | JUNE 2017 | 25