Horses afflicted with the skin disease hereditary equine regional dermal asthenia (HERDA, also called hyperelastosis cutis or HC) can develop external lesions from a variety of environmental factors. This includes everything from sunlight to contact with tree bark or fence boards … even other horses; keeping their fragile skin intact can be a full-time job. (Editor's note: This is part 2 of a series on one owner's experiences and struggles with a HERDA-affected horse. See part 1: When HERDA Strikes.)

According to Ann M. Rashmir-Raven, DVM, MS, associate professor of Large Animal Clinical Sciences at Michigan State University, HERDA-afflicted horses have a genetic mutation that affects collagen, the primary protein found in connective tissue such as skin, bone, cartilage, and tendon. The result is fragile skin that tears and scars easily in response to very small stresses, such as contact with a saddle