Mouth ulcers
Most mouth ulcers are temporary and heal on their own. The pattern matters more than any single sore: how often they appear, how long they last, where they sit in the mouth, and whether anything else has changed in your health.
An ulcer that does not heal in two weeks deserves a closer look. Recurrent ulcers in particular often point to something the mouth is responding to, whether a medication, a deficiency, or an underlying condition.
Most ulcers can wait for a routine visit. A few patterns warrant faster attention, especially when an ulcer is not healing or when other symptoms are present.
- An ulcer that has been present for more than two weeks
- An ulcer that is growing over time instead of healing
- Recurrent ulcers appearing every few weeks
- Widespread mouth ulcers covering large areas
- Ulcers that prevent you from eating or drinking adequately
- A painless non-healing ulcer on the tongue or floor of mouth
- An ulcer with hardened or irregular borders
- Ulcers paired with fever or feeling generally unwell
- Ulcers in a patient on chemotherapy or strong immunosuppressants (mucositis can become severe quickly)
- Difficulty swallowing because of mouth ulcers
| Pattern | What it often means | Why it matters |
|---|---|---|
| Single painful sore, heals in 1 to 2 weeks | Typical canker sore (aphthous ulcer) | Usually self-limiting; topical care speeds healing |
| Recurring ulcers every few weeks | Recurrent aphthous stomatitis or medication-related | Underlying contributor needs identifying |
| Cluster of small blisters on the lip | Cold sore (herpes simplex) | Contagious and managed differently than canker sores |
| Widespread ulcers during chemo or after starting a new medication | Drug-induced mucositis | Dose adjustment or topical care may be needed; coordinate with prescriber |
| Painless ulcer that has not healed in weeks | Needs prompt evaluation | Non-healing painless ulcers are the pattern of greatest concern |
Two of the most common types of mouth sores look different and have different causes. Canker sores (aphthous ulcers) appear inside the mouth on soft tissue: inner cheeks, tongue, soft palate, base of gums. They start as small painful spots and develop a white or yellow center with a red border. They are not contagious and the cause is often unknown.
Cold sores (caused by herpes simplex virus) typically appear on the lip border or just outside the mouth. They start as a cluster of small blisters that crust over. They are contagious through direct contact, especially during the blister phase. Antivirals can shorten an outbreak if started early.
The location (inside mouth vs lip border) is usually the giveaway. If the sores keep coming back in the same spot, that pattern often signals cold sores rather than canker sores.
Recurrent mouth ulcers can signal underlying conditions. Iron, vitamin B12, and folate deficiencies are among the most common. Inflammatory bowel disease (Crohn's especially) often includes oral ulcers as part of the disease pattern. Celiac disease can present with recurrent ulcers. Behcet's disease is a rarer cause but classic for recurrent oral and genital ulcers together.
A blood test panel and a careful history often identify the cause. Patients with frequent recurrence should not just keep treating the surface; finding the underlying contributor changes the long-term picture.
- Topical corticosteroids. Triamcinolone gel in Orabase or dexamethasone rinse, applied to active ulcers, reduces pain and speeds healing.
- Saltwater or baking soda rinses. One teaspoon in a cup of warm water, several times a day. Gentle and effective.
- Avoid alcohol-containing mouthwash. It burns ulcers and slows healing.
- Avoid trigger foods. Spicy, acidic, sharp, or very hot foods irritate active ulcers.
- Soft-bristle toothbrush. Hard brushing around an active ulcer prolongs healing.
- Magic mouthwash. A compounded rinse (lidocaine, antifungal, antihistamine) that helps with widespread ulcers or chemo mucositis.
The two-week rule is the simplest guide. Most ordinary ulcers heal in 1 to 2 weeks. An ulcer that has been present for longer, especially a painless one in a smoking or drinking history, warrants prompt evaluation rather than another round of over-the-counter treatment. The cost of a biopsy is small compared to the cost of a missed early diagnosis.
Recurrent ulcers also warrant a look beyond the surface. Treating the ulcer of the week without addressing the underlying cause leads to a long pattern of recurrence that often turns out to have an addressable explanation.
- For a fresh ulcer: saltwater rinses, soft toothbrush, avoid spicy and acidic foods, give it 1 to 2 weeks
- If it has been more than two weeks: schedule an exam
- If ulcers are recurrent: bring your medication list and recent labs to the visit
- If you started a new medication recently: tell your dentist or prescribing physician about the timing
- Seek urgent care if a painless non-healing ulcer, hardened borders, or systemic symptoms are present