What causes tail rubbing in mares?
The most universally noted cause of horses rubbing their tails is a certain type of parasitic worm, pinworms. If you are on a good deworming program, check with your veterinarian about recommendations to see if this is the problem. The sticky substance that pinworms deposit on the skin is what actually causes the horse to itch. So after you have dewormed your horse, you also need to wash under the tail to remove the irritation. Tail rubbing could also be in response to some type of dermatitis (skin irritation), and once it got started the horse just keeps scratching. If there are no other indications of allergy or other possible irritants such as flies, fungus, etc., contact your attending veterinarian. These are possible ideas but not all the possible ones, and diagnosis of health problems requires on-site diagnosis or at least consultation with a veterinarian familiar with your horses. Your veterinarian may prescribe particular deworming products or other drug therapies to help break this cycle.