How allergies are diagnosed in animals

How do we diagnose allergies?

The diagnosis of CAD is based on a correct diagnostic protocol, in which the most common causes of itching in the dog must always be ruled out first, like for example ectoparasitosis or bacterial or fungal infections.

Unfortunately, the presence of IgE antibodies to environmental allergens cannot be shown in all cases.

From a blood sample we can find out whether our animal presents antibodies to the saliva of fleas, to some microscopic pathogens like Malassezia or to environmental allergens.

In the case of food allergies, the best way to be able to rule out a food/diagnose is with an exclusion or elimination diet for a minimum of 8 weeks. This must be based on new proteins for the animal or on highly hydrolysed commercial foods. The food allergy tests serve to decide which foods we should avoid including in our elimination diet.

There has been a series of diagnosis criteria for a long time which the clinic can use to identify dermatological cases which are probably a CAD. A study by Favrot et al. demonstrated that if 5 out of the 8 clinical criteria indicated below are applied, it is possible to diagnose the CAD with a sensitivity of 85% and a specificity of 79% and would differentiate it from other ongoing diseases with recurring or chronic itching.

Favrot criteria

Diagnostic criteria of canine atopic dermatitis (at least 5 confirmed)

  1. Onset of signs before 3 years of life
  2. Dog living mostly indoors
  3. Itching which responds to glucocorticoids
  4. Pruritus sine materia at first (for example, alesional/primary itching)
  5. Front legs affected
  6. Auricular pavilions affected
  7. Auricular edges not affected
  8. Dorsolumbar area not affected

Vet Dermatol. 2010 Feb;21(1):23-31. doi: 10.1111/j.1365-3164.2009.00758.x.
A prospective study on the clinical features of chronic canine atopic dermatitis and its diagnosis.
Favrot C1, Steffan J, Seewald W, Picco F.