Dermatology cases can be a lot like looking for the proverbial needle in a haystack. Canine and feline skin has the habit of reacting to many insults in a similar manner. A pet may have an allergy, irritant reaction, bacterial infection, yeast infection, one of many different types of external parasites, an autoimmune reaction — even some types of cancer can develop a similar set of symptoms. Itchiness, hair loss, red skin, small bumps in the skin, pimple-like lesions, and scaling are symptoms of a laundry list of conditions.
The first part of a dermatological work-up always involves a physical exam. Unless the answer is then obvious, which it rarely is unless a pet is infested with fleas, I warn the owner that getting to the bottom of the problem may not be easy. We have to methodically start eliminating causes one by one, starting with the most likely culprits and moving down the list from there.
The process can take some time and often involves multiple rechecks. During the initial appointment, I’ll collect a thorough history and run a few simple and inexpensive tests, including:
- skin scrapings to look for mites that cause a few different types of mange
- skin cytology to check for abnormal skin cells and bacterial and yeast infections
- a fungal culture to rule out ringworm
The fungal culture can take up to three weeks to complete, so while we’re waiting for those results, I’ll treat for anything I have diagnosed (e.g., a skin infection) and oftentimes prescribe a medication to eliminate the possibility of external parasites that can be difficult to diagnose via a physical exam and the tests mentioned above.
From here, the diagnosis and treatment plan follow a personalized flow chart. It the pet’s problems are resolved with our first line treatment, we’ve found our answer. If the fungal culture was positive for ringworm, then obviously we head in that direction. If the pet is no better and the fungal culture is negative, we move on to the next phase in the work-up, which may involve a dietary trial to rule out food allergies, testing or empiric treatment for environmental allergies, or perhaps skin biopsies. I’ll choose a direction to head in based on what condition seems most likely based on the pet’s history and clinical signs. If that doesn’t pan out, then we backtrack and head down another path.
Complicating matters is the fact that many pets suffer from more than one dermatological condition at a time. Here’s a common scenario: A dog comes in for itchy, red, oozy, stinky skin. On the initial work up, we determine he has a yeast infection and successfully treat it. The redness, ooze, and odor are gone, but he’s still somewhat itchy. Continued testing reveals he is allergic to several different types of pollen and storage mites. His allergies are responsible for his continued itching and were the underlying reason he developed the infection in the first place.
To achieve ultimate success in derm cases, veterinarians often have to go looking for “the rest of the story,” as Paul Harvey would have said (I’m dating myself, aren’t I?). Dermatology is nothing if not an exercise in patience — for vets, owners, and pets.
Dr. Jennifer Coates