Your veterinarian can often diagnose hot spots simply by seeing the injured area, as they’re quite distinctive. They may take samples—such as with a swab or a slide pressed to the skin—or even recommend a biopsy, particularly if the area doesn’t look quite like a hot spot and they want to rule out other diseases. They may also recommend investigating an underlying cause, such as fleas, ear infections, or allergies—something that could have caused the original itch.