Skin disease due to a dietary component can occur due to a immunological reaction involving type 1 hypersensitivity response or due to an non-immunological reaction. They can occur at any age from puppies and kittens to old age.

Diagnosis of intolerance to food is often challenging and involves dedication. Serum allergy testing has limitations as not all reactions are antibody mediated and often normal individuals show serum IgE and IgG antibodies to various dietary proteins.

Ultimately the diagnosis should be based on response to a strictly conducted diet trial and subsequently challenging with the original diet.

The clinical signs or atopic dermatitis and adverse food reactions can be very similar and some dogs may have both conditions. Therefore in order to get maximum response a food trial should be performed in all allergic dogs and cats

Food Trial

  • Response to food trial can take several weeks (between 6-12)
  • During the trial the pet should be fed the prescribed diet only
  • This can be home-cooked with a novel protein and carbohydrate or a commercial diet can be used
  • Choice of protein depends on which proteins the animal has previously been exposed to
  • Commercially prepared hydrolysed diets are specially formulated to help with the diagnosis
  • No treats (chews, dog biscuits, sweets, flavoured toys, toothpastes and human foods are allowed during this period)
  • Cats should be kept indoors during the trial period
  • Dogs should be either muzzled or walked on lead to prevent scavenging
  • In multicat or multidog households the pets should either be fed separately or they should all be fed the trial food
  • Water only allowed
  • If there is a reduction of itch during the trial the pet must be challenged with the original diet. If the itch levels rise within a week to 10 days the original diet if implicated. This process can be repeated to further support the diagnosis.
  • Depending on the outcome a commercially prepared diet containing limited ingredients can be fed or provocation test by sequentially adding individual proteins and carbohydrates every 2 weeks can be performed to identify the diets that can be fed

These notes are only a brief explanation. If you wish to discuss any point further please do not hesitate to contact me.

Anita Patel (Veterinary Dermatologist)

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