Pinpointing atopic dermatitis in patients

The diagnostic process for atopic dermatitis—one of exclusion—can be challenging. In an interview with dvm360 on his lectures presented at the 2025 Veterinary Meeting & Expo (VMX), Jason B. Pieper, DVM, MS, DACVD, assistant professor at Iowa State University, goes into detail about this process. In this video, Pieper discusses one of the first causes of pruritus that are usually ruled out first in the diagnostic process and talks about what should follow.

Below is a partial transcript which has been lightly edited for clarity.

Jason B. Pieper, DVM, MS, DACVD: Diagnosing atopic dermatitis is a matter of just ruling out all other causes of itching, which can be somewhat difficult at times. But one of the big things that we typically start to rule out is parasites, looking you know, whether it's fleas that could potentially be causing flea allergies. Also other parasites, like Demodex, scabies, things like that, that can cause pruritus, so that's a big one.

The other big ones we're always ruling out is infections. So secondary infections, whether it's bacteria, fungal, whether it's Malassezia or dermatophytes, those are other causes of pruritus.

Then we get to other kind of aspects of autoimmune diseases, keratinization disorders, endocrinopathies, that can also cause actually pruritus but then, you know, be kind of subsequent to that of causes. But once you rule out those, then the other aspect that becomes a little bit more difficult is ruling out food allergies. And once you rule out food allergies, you know, based on either clinical criteria or doing a good diet trial for them, then once you do that, you actually back yourself into a corner to say, ‘Yes, this dog has atopic dermatitis now,’ and you feel comfortable with that.

With food and environmental allergies or atopic dermatitis, you know, some of it can be ruled out honestly just from the history alone. If the animal is highly seasonal, that pretty much tells you it's not a food allergy, unless they [client is] feeding [them] something seasonal. So that's probably one of the things, just from the history alone, you can kind of rule out food allergies and make it easier on yourself as a you know, a veterinarian and a diagnostician.