While still rare, equine sarcoidosis—not to be confused with sarcoid tumors, an unrelated skin condition—can appear in even the healthiest of horses. But don’t be too quick to treat sarcoidosis-associated hair loss, scaly and flaking skin, and crusting with creams, ointments, and lotions. According to Dutch researchers, it’s better to get a reliable diagnosis before starting treatments that might be useless, or worse, painful for your horse.

“An immune-mediated disease like sarcoidosis is not going to get better with washes and topical treatments,” said Marianne Sloet van Oldruitenborgh-Oosterbaan, DVM, PhD, Dipl. ECEIM, Specialist KNMvD Equine Internal Medicine, from the Department of Equine Sciences at Utrecht University. “Some horses’ skin actually becomes painful from all the various local treatments. It’s important to get an early diagnosis to know what you’re up against.”

Although sarcoidosis is visible on the skin, with its typical hair loss and crusting, flaking, scaling, and sometimes nodules, it’s sometimes a full-body disease that can attack the lungs and other organs—even bone marrow, Sloet said.

To better understand how sarcoidosis can affect the horse and to help owners and veterinarians determine treatment options, Sloet and colleague Guy C.M. Grinwis, DVM, PhD, Specialist KNMvD in veterinary pathology, also of Utrecht University, looked at 22 equine sarcoidosis cases at their university clinic between 2002 and 2011