How to Treat a Mouth Ulcer: Home Remedies, OTC, and When to See a Dentist

A painful sore inside your mouth — a canker sore or mouth ulcer — usually heals on its own within two weeks, but the right home remedies and over-the-counter products can ease the pain and shorten the worst days.¹² Most ulcers need nothing more than a saltwater rinse and time. A few need prescription treatment or a dentist’s evaluation. Here’s how to tell which kind you have, and how to treat it.

Most mouth ulcers are minor canker sores that heal in 1–2 weeks; major ulcers, herpetiform clusters, and contagious cold sores need different care — see our mouth ulcers overview to identify which type you have. Triggers like stress, oral injury, food sensitivities, SLS toothpaste, and vitamin deficiencies can bring on canker sores — our canker sores guide covers causes in depth.

• How do I get rid of a mouth ulcer fast? — Nothing makes a mouth ulcer disappear in 24 hours, but a warm saltwater rinse 2–3 times a day, an OTC benzocaine gel, and avoiding acidic and spicy foods can ease pain and reduce irritation while the ulcer heals.²
• How long do mouth ulcers last? — Minor canker sores (the most common kind) heal in 7–14 days.¹³ Major ulcers can take 2–6 weeks and sometimes leave a scar. Herpetiform clusters often clear within 1–2 weeks, though merged areas take longer.⁴ Any ulcer that lasts longer than 3 weeks should be seen by a dentist.
• What is the best over-the-counter treatment for a mouth ulcer? — Topical anesthetics with benzocaine (e.g., Orajel) numb the area; hydrogen peroxide mouth-sore rinses (e.g., Colgate Peroxyl) help cleanse the ulcer; protective pastes (e.g., Orabase) shield it while it heals.⁵
• When should I see a dentist for a mouth ulcer? — If the ulcer is larger than 1 cm, lasts more than two weeks, comes with a fever, recurs three or more times a year, or simply will not heal — a sore that won’t close up, especially with bleeding, a lump, or red or white patches, is the red flag for oral cancer.⁶

How to Treat a Mouth Ulcer at Home

Start with a warm saltwater rinse. Dissolve ½ teaspoon of table salt in 1 cup of warm water, swish for 30 seconds, then spit. Repeat 2–3 times a day, especially after meals.²⁷ It’s a low-risk first step that dental and medical sources consistently recommend, and it soothes the area by reducing irritation while the ulcer heals.

A few other home approaches that have at least some support:

• Baking soda paste — Mix ½ teaspoon of baking soda with a few drops of water to form a paste. Dab it on the ulcer 3–4 times a day. The mild alkalinity neutralizes acidic foods that aggravate the sore.⁷
• Diluted hydrogen peroxide rinse — A 1:1 mix of 3% hydrogen peroxide and water, used as a rinse and spit, can reduce bacterial load on the ulcer. Use no more than twice a day, and never swallow.⁵
• Honey — Dabbing a small amount of medical-grade honey on the ulcer 3–4 times daily has shown some benefit in small trials. Do not give honey to children under 12 months because of botulism risk.
• Aloe vera gel — Pure aloe gel applied directly to the ulcer may ease pain and shorten healing in small studies.
• Ice chips — Sucking on a small ice chip held against the ulcer numbs the area for short bursts of relief, especially before meals.

While the ulcer heals, eat cool, soft, low-acid foods: cooked oats, mashed potato, scrambled eggs, smoothies made with non-citrus fruit. Avoid yogurt and citrus — both are more acidic than they feel — along with crunchy chips, spicy dishes, and very hot drinks. Stay hydrated, and switch to an SLS-free toothpaste if your usual one seems to trigger flares. There is no quick fix for a mouth ulcer; the goal is pain relief and protecting the sore while it heals.²

Over-the-Counter Mouth Ulcer Treatments

The most effective over-the-counter products are topical oral anesthetics — gels and liquids that contain benzocaine. Dab a small amount directly on the ulcer with a clean fingertip or cotton swab, up to four times a day. Benzocaine numbs the sore so you can eat, drink, and brush without flinching, but it does not shorten healing.⁵⁸ Lidocaine works the same way but is prescription-only as an oral rinse or viscous solution in the U.S., so it belongs in the next section.

Beyond anesthetics, four OTC categories help in different ways:

• Hydrogen peroxide mouth-sore rinses — Products like Colgate Peroxyl help cleanse the area and reduce bacteria around the ulcer, which may shorten the painful phase. Follow the label, typically twice a day. Chlorhexidine rinses such as Peridex are prescription-only in the U.S. and should be used only if a dentist or doctor recommends them.⁵⁸
• Protective pastes and patches — Pastes containing carmellose (Orabase) form a thin film over the ulcer to shield it from food, drink, and the tongue. A dissolvable patch works the same way and stays in place for hours.
• Anti-inflammatory gels — Choline salicylate gels (Bonjela and similar, more widely sold in the UK and Australia) reduce inflammation and pain. They are not for children under 16.
• Baking soda and saltwater rinses, store-bought — Many drugstore “mouth sore” rinses are simply buffered sodium bicarbonate. A homemade rinse works just as well and costs nothing.

A safety note on benzocaine: Do not use benzocaine products in children under 2. Adults and older children should follow the Drug Facts warnings — rare but serious cases of methemoglobinemia, a blood-oxygen disorder, have been linked to overuse.⁹

If you get mouth ulcers three or more times a year, ask your dentist or doctor whether to check your vitamin B12, iron, or folate levels. Vitamin B12 supplementation can reduce recurrence in people who are deficient, but it is not a treatment for the ulcer you have today.¹⁰

Prescription Treatments for Severe or Recurrent Mouth Ulcers

For an ulcer that is unusually large, painful, or one of many that keep coming back, prescription treatments work where OTC products fall short. Most options aim at the inflammation driving the sore, not the pain.

• Topical corticosteroids — Triamcinolone acetonide 0.1% in Orabase (a steroid in a sticky paste) is the most commonly prescribed first line. Stronger options include clobetasol gel and dexamethasone rinses for ulcers that don’t respond.¹¹¹²
• Prescription rinses — A dentist or doctor may prescribe chlorhexidine (Peridex) to reduce bacteria around the ulcer, or a lidocaine rinse for pain relief. Either is sometimes combined with a steroid when the ulcer is extensive or particularly painful.⁸
• Cautery — A dentist or doctor may use silver nitrate or a dental laser to seal a stubborn ulcer in a single in-office visit. It does not speed healing of the tissue underneath, but it shuts down the pain quickly.⁵
• Systemic medications — For severe recurrent aphthous stomatitis that fails topical therapy, doctors sometimes prescribe colchicine, oral prednisone, or — as a last resort — thalidomide. Thalidomide carries a serious teratogenicity warning and is reserved for refractory cases under specialist supervision.¹¹
• Nutritional support — If blood work shows a deficiency, your doctor may prescribe B12, iron, or folate supplementation alongside topical treatment.¹⁰

If your dentist suspects an underlying condition — Crohn’s disease, celiac disease, Behçet’s syndrome, lupus, or HIV — driving your recurrent ulcers, you’ll be referred for that workup. Treating the underlying condition usually quiets the ulcers.

When to See a Dentist About a Mouth Ulcer

Most mouth ulcers heal on their own within two weeks. See a dentist or doctor if:

• The ulcer lasts more than 2–3 weeks — Persistent ulcers can signal an underlying condition or, rarely, oral cancer.⁶
• The ulcer is larger than 1 cm or unusually painful — Major aphthous ulcers respond best to prescription corticosteroids and should not be left to heal alone.¹¹
• You get 3 or more ulcers per year — Recurrent aphthous stomatitis can signal vitamin deficiency, food sensitivity, or systemic disease and warrants a workup.¹⁰
• The sore won’t heal, bleeds, or has red or white patches around it — A sore that won’t go away — whether or not it hurts — can be an early sign of oral cancer. See our canker sore vs. cancer guide for the differences.⁶
• You have a fever, swollen lymph nodes, or trouble swallowing — These point to an infection — such as HSV cold sores, hand-foot-and-mouth disease, or herpangina in children — rather than a simple canker sore.
• The sore appears on the outside of the lip or face — That’s likely a cold sore (HSV), not a canker sore, and is treated differently.

Bring a short list to the appointment: how long the ulcer has been there, how many you’ve had in the past year, any medications you take, and any other symptoms you’ve noticed. That history is what helps your dentist tell a simple canker sore from something that needs further evaluation.