Bit sores and oral ulcers in a horse’s mouth


Even now and then, your horse will throw you a curve ball and end up with a bit sore or other mouth problem. It could be minor, like needing bit guards or something viral or dental-related. Ah, horses, always keeping us on our toes.  


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What are bit sores? 


  • Bit sores are the cracks in the corners of your horse’s mouth. It could be a crack, an open sore, flakey skin, cut, pimple, or ulcer. Really, a bit sore is some new irritation in the mouth corners where the bit rests. 


  • But – not all bit sores are caused by the bit. Figuring this out requires some detective work, then you can find the best solution for healing the sore.

summer sore in the corner of a horse mouth

This bit sore is actually a summer sore.


Causes of bit sores in the corner of the mouth


The actual bit


  • Perhaps the size, thickness, metal, placement, joint system, and hinge system of the bit are pinching, pulling, rubbing, stabbing, or otherwise causing damage to your horse’s mouth. 


  • *** Many bits are made from non-traditional metals and materials and could create an allergy. It’s worth exploring if your horse’s sores are a huge mystery. 

The bridle


  • It’s also possible that your noseband and flash (or other noseband accessories) are too tight or not placed correctly.  

Read more about the science of tight nosebands here


clipped gray pony head in bridle

Don’t underestimate the power of properly fitted tack 


Foreign bodies in the mouth corners


  • There’s always a chance that your horse gnawed on something that’s now stuck in his mouth. Foxtails are notorious for burrowing into tissue. For wood-chewing horses, splinters are a possibility, too. Even sharp bits of hay can create damage.  

Summer sores


  • When a fly infected with a specific parasitic worm gets into a wound or soft tissue, summer sores can happen. A tiny opening in the tissue becomes wildly irritated and open as the worm sets up his house there.  


  • While summer sores are usually seen around the lower legs, they can also happen near horses’ eyes, genitals, and mouths as the softer tissue are susceptible to this infection. 


  • Summer sores are hard to heal, sometimes taking upwards of a year. Your vet can help with both topical and systemic medications to contain the problem. 

Grazing muzzles


  • Ideally, the grazing muzzle you use should not create sores or rubs on your horse. But, sometimes, it happens. Rubbed hair and shortened whiskers are the best clues that the halter and muzzle need some adjustment or rub prevention. 


  • Some horses, especially with short or very long pasture grass, use their teeth against the muzzle. You will see the muzzle wear, and the gums may get irritated, too. Try mowing the grass to an “easier” height or rotating pastures. You may want to try out a different muzzle style, too. 


up close shot of horse wearing a grazing muzzle


Preventing bit sores


  • Hopefully, it’s easy to prevent bit sores with a few changes to the bridle and bit. You can also use bit guards to protect the mouth from the hinge of the bit rings. 


  • For horses that tend to have dry and cracked skin in the corners of their mouth, you could apply an A & D ointment or petroleum jelly before tacking up. Check with your vet for their recommendation. 


  • If your horse has wounds from wood chewing, hay, or foxtails, it’s time for some barn management changes. Curb wood chewing by offering forage in various slow feeders and increase your horse’s turnout and exercise. Hay may need soaking or steaming to become softer.  


  • For foxtail control, this may require some significant pasture renovations, more frequent mowing, or a different rotational system.  

Other oral ulcers and sores


  • Oral sores are not limited to the mouth corners. Gums, the tongue, the cheeks, and the palate can all have ulcers or wounds. And yes, it’s a good idea to take a look, and smell, in your horse’s mouth daily. 

Dental issues create sores


  • Hooks and sharp edges on teeth catch on cheek and tongue tissue to create wounds. These cuts can be magnified when nosebands and bits are not kindly fitted.


  • Dental abscesses also create wounds. An abscess is a pus-filled infection, and when enough pressure builds, the abscess will rupture through the gums. Hopefully, your horse has told you something is wrong before this happens, by not eating well or chewing differently than usual. There is often a horrible smell associated with tooth abscesses. 


horse tooth with sharp edge pointing to the tongue

This hook on the molar (right side) is pronounced enough to cause oral ulcers and pain. 


Vesicular stomatitis


  • This viral disease is also transmittable to other horses, livestock, and humans. Vesicular stomatitis causes open ulcers in and around the mouth, legs, hooves, and genitals. The lesions can happen in one or more locations. The ulcers may slough the tissue off and even lead to laminitis.  


  • The ulcers are painful and affect a horse’s chewing and eating. Isolation and veterinary intervention are mandatory, but supportive care can be given. Horses usually recover on their own in a few weeks or months.  


Weeds, hay, and foreign bodies


  • Those naughty foxtails and weeds may also impact the inside of your horse’s mouth. Daily inspections and smelling of the mouth can alert you to possible problems. A horse may eat or drink differently if stabbed by hay, weeds, or a foreign body. 


  • What’s the biggest thing you can do to help your horse? Know what’s normal and what’s new or unusual. Know how they eat and drink, what their gums, tongue, and teeth look like, and make proactive changes if you find something isn’t right. 



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For western bridles, a little bit of flair

Traditional bit guards with easy-on fastener

My favorite all-purpose first aid ointment to have around


Deterrents if your horse likes to eat fencing and things

Hydrophane Cribox 8 oz. tub – 8Oz

Farnam Chew Stop Aerosol


Safety break-away halter for grazing muzzles.



A boxy muzzle may stand away from your horse and help stop sores. Also available in raspberry, blueberry, and black colors.

Use code 15PROEQUINE for a lovely discount on this muzzle

This bridle design has a different noseband and flash configuration

Hunter bridles rarely come with flashes


This bridle doesn’t have a flash

Brown replacement noseband

Black replacement noseband





Thank you!


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