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University of Minnesota Extension

Plants that cause mouth blisters in horses

Quick facts

  • Don’t feed hay with moderate amounts of foxtail and sandbur seed heads, and/or ticklegrass seed heads and stems.

  • These grasses can cause trauma to the mouth and gut of horses.

  • Timely mowing can prevent seed head production of these grasses.

  • There are no herbicides available for these grasses in grass hayfields or pastures.

Oval shaped seeds, some with sharp ends.
Foxtail seeds

What plants cause mouth blisters?

  • Foxtail

  • Sandbur

  • Ticklegrass

Don’t feed hay containing moderate amounts of foxtail and sandbur seed heads, and/or ticklegrass seed heads and stems.



  • Bottle brush-like, light green seed heads


  • Barbed, slender and purple tinged seeds


  • Green to purple and shiny seed heads

  • Tan seed heads when mature

  • Rough branches of flowers

Foxtail seed head.
Foxtail seed head.
Sandbur seeds and bur
Microscopic barbs of ticklegrass
Microscopic barbs of ticklegrass

Where are they found?



Ticklegrass embedded in horse’s mouth
Ticklegrass embedded in horse’s mouth

These plants can cause physical trauma to the horse’s mouth, gut, and sometimes the skin.

Ticklegrass, sandbur and foxtail seed heads can embed into the horse’s lips, mouth, gums and lower gut when eaten. This is most common when baled in hay and rarely occurs in fresh forage.

The leaves of sandbur and foxtail don’t cause harm to horses. Horses can graze these but we don’t recommend them as a forage species.

Signs of trauma 

  • Blisters or ulcers on the lips or mouth after eating these plants

  • Weight loss occurs from damage to the gut if horses eat these plants long term


Remove the plant source from your horse. You can provide supportive treatment for the blisters and ulcers such as rinsing with water or a topical cream.


Bale of hay with dark purple areas that is ticklegrass.
Hay with a lot of ticklegrass (dark or purple areas)

Mowing is a relatively effective way to control all three grasses. Timely mowing can eliminate or reduce seed production.

In grass pastures or hay fields, there are no herbicides available for control of these grasses. Spot treatment with glyphosate is an option. But good pasture management will help reduce or eliminate weeds.


  • Foxtail and sandbur are annuals reproducing from seed.

  • Ticklegrass is a perennial.

Authors: Krishona Martinson, Equine Extension specialist, Lynn Hovda, DVM, adjunct assistant professor and Mike Murphy, DVM, former professor, College of Veterinary Medicine

Reviewed in 2021

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