Every spring, horse owners notice it: horses rubbing, scratching, and stamping as tiny insects appear. Many assume midges or blackflies are the cause of seasonal irritation, commonly known as sweet itch. But decades of veterinary research show the truth is more nuanced — and far more important for prevention and management. 1. Exposure Doesn’t Equal Severity Two horses can graze side by side in the same pasture. One barely reacts. The other develops severe lesions. Why? Resea