Understanding PSPP in canine otitis externa

During this interview with dvm360, ahead of his upcoming lectures at the 2026 Veterinary Meeting and Expo, Darin Dell, DVM, DACVD, a veterinarian from Wheat Ridge, Colorado, shares the meaning behind the acronym PSPP and how it pertains to canine otitis patients in the veterinary clinic.

Below is a transcript of the video, edited lightly for clarity.

dvm360: Starting with your name, can you tell us a little bit about yourself?

Darin Dell, DVM, DACVD: My name is Dr Darin Dell. I'm a veterinarian here in Wheat Ridge, Colorado, just west of Denver. I started working at a veterinary clinic in my little hometown when I was 14. So I was indoctrinated early. Started out cleaning kennels, mopping the floors, then holding animals, then answering the phones, and helping the doctor on farm calls. So veterinary medicine is really how I grew up. That's why I went to vet school.

[I] went to the University of Illinois, graduated in 2001, worked for several years in general practice, and then did some overnight ED, before I decided to become a dermatology resident. Life is a whole lot easier as a dermatology resident [and then] as a dermatologist. It's also just clearly the specialty that I love [and] makes sense to me. I love making a difference for folks with these long-term problems, and it makes me happy.

dvm360: What does PSPP stand for in the context of diagnosing otitis externa?

Dell: Oh, I'm so excited we get to talk about this. So PSPP stands for primary, secondary, predisposing, and perpetuating causes of otitis externa, not something I learned in veterinary school. I don't think any of the veterinary schools teach it. It's something you learn as a dermatology resident. So it's a way to really unlock this mystery of: What do I do with this ear infection, and what should I do with the next one?

Primary stands for things that cause ear disease. So there's really not a long list of those. The common ones are allergy, parasites, foreign bodies, and trauma—one of those things has to happen, right? So that's where we need to think about: If we're going to stop chronic ear disease, we have to go to the primary problem.

Secondary is probably the most confusing one, because that's where infection falls in. So secondary means that it can cause disease if there's already a problem with the ear. So your ear canal already has bacteria and yeast in it; that's normal. But it's not until you add an allergy or you add a parasite like ear mites that those bacteria become a problem.

Predisposing is all the things that our clients think cause ear infections. So that's the droopy ears, that's swimming. Everybody wants to say, "Oh, my dog swims, and that causes ear infections." No, that's a predisposing problem, sure, but there are plenty of dogs that swim and never have an ear infection. So it's not a primary cause. And again, it's easy to be confused. It's easy for our clients because these things have been said for decades, right? It's not like they invented this. Somebody told them. So really, kind of putting a structure to it helps them look at it and say, "Oh yeah, I guess you're right. My last dog swam all the time and didn't have ear infections. It's not just that."

And then the last one perpetuating is the one that often gets missed. So that's the one that nobody talks about a lot. That's after we have an ear infection, [and] after we have something going on in the ear, the ear takes time to heal, so for a while it makes more ear wax than normal, and there's something called epithelial migration, which is how earwax leaves the ear, and that's suppressed after we have an ear infection. So that's a perpetuating cause. That's why sometimes veterinarians will treat an ear infection, it looks great, and then they stop everything at 10 days or 7 days, and then in 2 weeks, it's back. It's because you have these perpetuating factors that you just didn't give them enough time to work themselves back to normal.

So it really helps, as you're talking to clients, to put some framework to it, and helps us, as I'm teaching otitis, to say, "OK, let's break down some of the myth. Because yes, these things are all important, but they fall into different buckets." If you really want to solve the problem, you have to go to the primary issue and resolve that.