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