Most ulcers under the tongue are canker sores (aphthous ulcers) that heal on their own within one to three weeks. While you wait, the right combination of rinses, topical treatments, and dietary adjustments can cut pain significantly and speed healing. The underside of the tongue is one of the thinnest, most sensitive areas in your mouth, which is why ulcers there tend to hurt more than sores on your gums or inner cheeks.
Why Ulcers Form Under the Tongue
The tissue on the underside of your tongue and the floor of your mouth is soft and poorly protected compared to tougher areas like the roof of your mouth. That makes it especially vulnerable to a few common triggers:
- Mechanical trauma: Biting your tongue, scraping it against a rough tooth edge, or irritation from braces or dental work.
- Nutritional gaps: Low levels of vitamin B12, iron, folic acid, or vitamin C are strongly linked to recurring canker sores. In clinical case reports, patients with persistent mouth ulcers often had B12 levels well below the normal range, and their sores resolved after supplementation.
- Toothpaste ingredients: Sodium lauryl sulfate (SLS), the detergent that makes toothpaste foam, can irritate sensitive oral tissue. Study results on SLS-free toothpaste are mixed. One trial of 90 people with recurring ulcers found that switching to SLS-free toothpaste didn’t reduce the number of sores, but participants reported less pain and slightly faster healing while using it.
- Stress and immune changes: Periods of high stress, illness, or hormonal shifts often trigger outbreaks in people who are prone to canker sores.
What Type of Ulcer You Likely Have
Not all mouth ulcers behave the same way. Minor canker sores, the most common type, are smaller than a pea and heal within a few weeks without scarring. Major canker sores are larger than one centimeter, extremely painful, and can take months to fully heal, sometimes leaving scars behind. A rarer type, called herpetiform canker sores, shows up as clusters of tiny pinpoint sores rather than a single ulcer. These typically heal within about two weeks.
The size, shape, and behavior of your sore matters because it tells you how long to expect it and when to seek help.
Home Treatments That Help
Salt Water Rinse
A warm salt water rinse is the simplest and most widely recommended first step. Dissolve half a teaspoon of table salt in a glass of lukewarm water. Swish gently around the sore for 15 to 30 seconds, then spit. Repeat two to three times a day, especially after meals. Salt water reduces bacteria around the ulcer and draws fluid from swollen tissue, which eases inflammation. It will sting briefly on contact.
Honey
Applying a small amount of honey directly to the ulcer can shorten healing time. A study comparing honey-treated ulcers to untreated ones found a statistically significant difference in healing by day seven. The challenge is that saliva dilutes honey quickly, so pressing a small dab onto the sore and keeping your tongue still for a minute or two helps. Applying it at least twice a day, or more often, improves results.
Over-the-Counter Numbing Gels
Topical gels containing benzocaine or lidocaine can temporarily numb the area, making it easier to eat and talk. Apply a small amount directly to the ulcer with a clean finger or cotton swab. These products provide relief for 20 to 60 minutes, depending on the formula. Avoid eating or drinking hot liquids immediately after application, since you won’t feel temperature as accurately while the area is numb.
Avoid Irritating Foods
Acidic foods like citrus, tomatoes, and vinegar-based dressings, along with spicy or crunchy foods, will aggravate the sore and slow healing. Stick to soft, cool, or room-temperature foods while the ulcer is active. Yogurt, mashed potatoes, scrambled eggs, and smoothies are all gentle on the tissue under your tongue.
When OTC Treatments Aren’t Enough
If you have a large or especially painful ulcer that isn’t responding to home care after a week, a dentist or doctor can prescribe a steroid dental paste. These pastes contain a corticosteroid that reduces inflammation directly at the sore. You press a small amount onto the ulcer, and the paste adheres to the wet tissue, forming a protective film that also delivers the medication. Prescription-strength options work faster than over-the-counter products for stubborn or major canker sores.
For people who get frequent outbreaks, a doctor may order blood work to check vitamin B12, iron, and folic acid levels. In documented cases, patients with recurring canker sores had B12 levels roughly half of the lower normal limit. Correcting the deficiency through supplements or dietary changes resolved the ulcers in those patients. If your sores keep coming back every few weeks or months, a simple blood test can rule this out.
Reducing Future Outbreaks
If you’re prone to under-tongue ulcers, a few changes can lower the frequency. Switching to an SLS-free toothpaste is a low-risk experiment, and even if it doesn’t prevent sores entirely, it may reduce how much they hurt. Check that your diet includes good sources of B12 (meat, fish, eggs, fortified cereals), iron (red meat, spinach, lentils), and folic acid (leafy greens, beans). If you have a sharp tooth edge or rough dental appliance that repeatedly irritates the underside of your tongue, getting it smoothed or adjusted by a dentist removes a direct trigger.
Managing stress through sleep, exercise, or whatever works for you also matters. Many people notice their outbreaks cluster around exams, deadlines, or periods of poor sleep.
Signs That Need Professional Attention
The underside of the tongue and the floor of the mouth are among the most common sites for oral squamous cell carcinoma. That sounds alarming, but the distinction between a canker sore and something more serious is usually straightforward. A standard canker sore hurts, has a clean round or oval shape, and starts shrinking within a week or two.
Get a sore evaluated by a doctor or dentist if it lasts longer than two weeks without improving. Other warning signs include:
- A bump or firm lump under the skin where the ulcer is
- Red, white, or mottled patches that don’t go away
- Bleeding from the sore that persists
- Texture changes like rough patches, cracking, or crustiness
- Visible swelling or lumps in your neck, cheek, or jaw
Your doctor or dentist will visually examine the area and feel for firm tissue. If anything looks unusual, a biopsy can provide a definitive answer. Most ulcers under the tongue are completely harmless, but the two-week rule is a reliable guideline for knowing when to get a closer look.