A Practical Approach to the Itchy Horse

The diagnosis and management of the itchy horse is a process built on having an understanding of the pruritic diseases most likely to be present in your geographic area along with data provided through history taking, a through dermatological examination, selected diagnostics (cytology, skin scraping, fungal culture) and the assessment of response to therapy. The most common differential diagnoses for the pruritic horse include insect bite hypersensitivity (IBH), atopy, food sensitivity, pediculosis,Chorioptes, Psoroptes, trombiculidiasis (chiggers or harvest mites), contact hypersensitivity, and those dermatoses that are variably pruritic including dermatophytosis, bacterial pyoderma, dermatophilosis, pemphigus and drug eruption.

Important historic points include management (e.g. stable vs. pasture; diet), age of onset (e.g. 2–4 years and 1–6 years for IBH and atopy, respectively) and seasonality. Seasonal pruritus problems are most commonly associated with IBH and atopy (spring, summer, fall), trombiculidiasis (fall), chorioptic mange and pediculosis (winter). Attention must be paid to whether the pruritus has created the lesions (e.g. IBH, atopy) or the lesions were noted before pruritus (e.g. dermatophytosis, bacterial pyoderma, pemphigus) - i.e. is it “an itch that rashes or a rash that itches”? History taking should include documentation of medications being taken when the pruritus/lesions developed (e.g. drug eruption, contact hypersensitivity) and response to medications (e.g. glucocorticoid responsive - IBH, atopy, food sensitivity). [...]