Why do horses rub their tails?

What could be causing a healthy mare to rubbing her tail raw?

Q: My mare has been rubbing her tail against her stall wall. She is on a deworming program, which includes regular fecal egg counts, so I can’t imagine it’s related to parasites. What else might be causing her to do this? (She doesn’t do it when she’s in the field, only in her stall.)

Horse scratching his back on a wooden fence. Mud and dirt visible on horse's back.
A dirty udder can cause tail rubbing in a mare; the udder is itchy but the horse doesn’t know how to get to the itch.

A: Well done that you are already considering one of the differentials on my list for tail rubbing! Horse pinworms (Oxyuris equi) can certainly cause tail rubbing but thankfully this is actually quite rare. The worms do not typically show up in fecal floats and instead require special surface tape sampling to find. However, with a routine deworming program it is very unlikely that pinworms are causing your mare’s rubbing issue, so I think you are well covered here. 

Other potential causes of tail rubbing to consider include insect bite hypersensitivity, environmental allergies, dry skin on the tail or a mite called Chorioptes bovis

A dirty udder can cause tail rubbing in a mare; the udder is itchy but the horse doesn’t know how to get to the itch. She can’t use her hoof to scratch the itch there and most mares aren’t flexible enough to reach around to bite the affected area, so they attempt to “reach” the udder by scratching the tail. 

Boredom can also lead a horse to tail rub. In these cases, something fun in the stall is helpful, like a Jolly Ball, a grain-dispensing toy or a hay-dispensing contraption. Of course, less time in the stall means less stall boredom, so turn the horse out more if that’s possible.

While the source of your mare’s behavior certainly could be boredom, you’ll want to determine whether the cause is something treatable first. I recommend that you start by contacting your veterinarian to help you rule in or out potential physical causes of the rubbing. 

Julia E. Miller, DVM
Animal Dermatology Clinic 
Louisville, Kentucky

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