Vet Tips 2025: What Causes Oral Ulcers in Horses—And How to Prevent Them 🐴👅

By Dr Duncan Houston BVSc

When your horse goes off feed or looks uncomfortable around the mouth, it could be more than picky eating—oral ulcers may be the cause. These painful sores can make chewing and swallowing difficult, and if left untreated, may lead to weight loss or secondary issues like colic. Here's what every horse owner should know. 🩺🐎

Case in Point: When Pain Starts in the Mouth 📉👄

One case I saw involved a horse recovering from laminitis and being treated with phenylbutazone (Bute) in paste form. The horse became dull, stopped eating well, and looked generally unwell. Upon oral exam, we found large ulcers on the tongue and throughout the mouth—likely from the bute paste not being swallowed quickly. 💊😟

Common Causes of Oral Ulcers in Horses ⚠️🧠

While mouth ulcers can arise from several different sources, they’re almost always painful. Common causes include:

• 💊 Phenylbutazone (Bute)—especially in paste form if it lingers in the mouth
• 🌾 Grass awns (especially foxtail) or sharp plant material in hay
• 🦠 Viral diseases such as vesicular stomatitis
• 🧬 Immune-mediated conditions that trigger ulceration
• 🪥 Dental trauma or foreign bodies

Each case needs careful assessment to determine the correct treatment. 🧪

Phenylbutazone (Bute) and Mouth Ulcers 💊👅

Bute paste is widely used and generally safe—but in some cases, the paste may sit in the horse’s mouth and cause chemical burns or irritation. 🧨

Prevention Tips:

• 🐴 Ensure the horse swallows the paste quickly
• 🚿 Flush the mouth with water 5–10 minutes after dosing
• 🧼 Monitor for signs of drooling, feed aversion, or lip smacking

If you see any change in eating behavior while on medication, perform an oral exam or call your vet. 📞

Hay and Grass Awns: The Hidden Culprit 🌾🔍

Foxtail grass and other plants with sharp awns can get baled into hay—especially during drought years or when feeding lower-quality forage. These awns:

• ⚠️ Pierce the gums and tongue
• 🦠 Introduce bacteria or cause abscesses
• 💢 Trigger ulcers and inflammation

Always inspect new hay batches for sharp stems or invasive weeds before feeding. 💡

Other Causes of Mouth Ulcers in Horses 🧠📋

• 🦠 Viral diseases: Vesicular stomatitis, equine viral arteritis (EVA)
• 🧬 Autoimmune conditions that trigger chronic inflammation
• 🔧 Improper dental work or trauma from a bit or sharp teeth
• 🩺 Bacterial infections secondary to other oral trauma

If symptoms persist, your vet may recommend bloodwork, biopsy, or viral testing. 🧬

Signs Your Horse May Have Mouth Pain 👀⚠️

• 🥣 Sudden aversion to feed or treats
• 💧 Drooling or excessive salivation
• 🥕 Dropping feed or slow chewing
• 🗣️ Avoidance of the bit or bridle
• 🧪 Bad breath or visible sores
• 🤧 Nasal discharge (especially one-sided)

If you see any of these signs, check the mouth and call your vet. 🩺

Treatment for Oral Ulcers 💊🛠️

• 🛏️ Rest the mouth—avoid using a bit or hard feed
• 🧊 Provide soft, soaked food or complete feeds
• 💧 Use antiseptic rinses if recommended by your vet
• 💊 Switch or discontinue irritating medications
• 🧪 Treat infections with appropriate antibiotics if needed

Healing usually occurs within days to weeks—but ongoing monitoring is essential. 🧠

How to Prevent Future Ulcers 🛡️🐴

• 📦 Check every new hay delivery for foreign or sharp material
• 💊 Ensure medications like bute paste are swallowed quickly
• 🪥 Maintain regular dental exams
• 🧼 Monitor for signs of discomfort after worming or drug administration

Prevention starts with awareness and quality control. ✅

Need Help With Oral Ulcer Recovery? Ask A Vet 📱👄

Concerned about ulcers in your horse’s mouth or unsure if bute is to blame? Connect with a licensed vet at Ask A Vet today.

Download the Ask A Vet app for 24/7 support on equine oral health, safe medication use, and hay inspection tips. 🐴📋

Final Thoughts: A Healthy Mouth = A Happier Horse 💛🦷

Oral ulcers can derail appetite, mood, and overall health. Whether from medications, hay, or infections, your horse depends on you to recognize early signs and take action. 🧠❤️

Need expert guidance now? Visit Ask A Vet for real-time support from equine dental pros. 🐴🩺