Which diagnostic test is most appropriate to support flea allergy dermatitis in a dog with pruritus?

• A. Flea comb or flea counts
• B. Wood’s lamp examination
• C. Skin biopsy
• D. Blood culture

Answer: (A)

Detecting fleas or flea dirt directly on the animal is the most practical way to support flea allergy dermatitis in a pruritic dog. A thorough flea comb run through the coat can reveal live fleas or dark flea feces (flea dirt), which strongly points to flea-related inflammation since FAD is triggered by flea saliva. Even if fleas aren’t seen at every visit, finding them or persistent flea dirt provides concrete evidence that fleas are a contributing factor, and starting or adjusting flea control with close follow-up can confirm the diagnosis through improvement.

Wood’s lamp examinations are useful for some fungal infections, like certain Microsporum species, but they don’t help assess fleas. A skin biopsy can show dermatitis but isn’t specific for flea allergy and is usually used when trying to rule out other conditions or assess chronic changes. Blood culture isn’t relevant to diagnosing flea allergy dermatitis in this context.