Headshaking, however, is different. It takes on a whole new meaning when this behavior is performed frequently, if not constantly, while the horse is being ridden, and nothing about this behavior is normal. Headshaking is the act of the horse flipping its nose into the air, sometimes even shaking its head from side to side. This type of headshaking, the pathologic manifestation, also often involves rubbing the muzzle and sneezing. Not only is this behavior irritating and uncontrollable, but can seriously hamper the ability of the horse to perform in many disciplines.
Some horses even become dangerous as their headshaking takes on an obsessive and violent form.
These horses might appear as if a bee has flown up their nose. Although this disorder has been reported to occur in horses for decades, one exact etiology has never been elucidated. Until recently, many people gave up on their headshaking horses. There did not seem to be anything that stopped the behavior, making it impossible to enjoy riding that horse. For many years, people surmised that headshaking was purely a rider or training problem, not a medical disorder.