Headshaking

Headshaking is a condition where the horse or pony shakes its head continuously, often while being ridden.

Originally considered a bad habit, it is now thought that some horses are allergic to certain pollens, which causes them to headshake. However horses also normally react to flies, and headshaking may be a fly defence overreaction even if flies are not present. Sometime the halter or bridle is maladjusted or irritating the animal as the rider is using rein commands.