Mouth Ulcers: Causes, When to Worry, Treatment That Actually Helps

Mouth ulcers — the painful, recurring sores on the inside of cheeks, lips, tongue, or gums — affect about 20% of UK adults at any given time. Most are minor and self-limiting. A small minority signal something that needs medical attention. Here is the diagnostic and treatment ladder.

The three main types

Minor aphthous ulcers (the common one)

Round or oval, 2–10 mm, white or yellow base with red border. Painful but self-limiting. Heal completely in 7–14 days without scarring. Account for about 80% of ulcer cases. Most patients have one to several at a time, sometimes recurring.

Major aphthous ulcers

Larger (10+ mm), deeper, last 2–6 weeks. Can scar on healing. Less common, often more disabling.

Herpetiform ulcers

Multiple tiny (1–3 mm) ulcers that cluster and may merge into larger lesions. Despite the name, not related to herpes virus.

Common triggers

Most aphthous ulcers have no single identifiable cause but recognised triggers include:

• Local trauma: biting the cheek or lip, sharp tooth edges, dental appliance friction. The most common single trigger.
• Stress and anxiety: well-documented association with ulcer outbreaks in susceptible patients.
• Certain foods: citrus, tomato, chocolate, nuts, spicy foods. Individual; not universal.
• Toothpaste containing sodium lauryl sulphate (SLS): some patients see substantial improvement on switching to SLS-free toothpaste.
• Hormonal changes: menstrual cycle, pregnancy.
• Vitamin and mineral deficiencies: B12, folate, iron, zinc deficiencies are well-documented in patients with recurrent ulcers.
• Certain medications: NSAIDs, beta-blockers, methotrexate.

When ulcers signal something else

Most ulcers are benign and self-limiting. The presentations that warrant medical attention:

• Single ulcer lasting more than 3 weeks: any persistent oral ulcer needs assessment to rule out oral cancer. The 3-week threshold is the standard NHS referral criterion.
• Hard, painless mass with overlying ulcer: different presentation from typical painful aphthous ulcers; high concern for malignancy.
• Ulcer with adjacent lymph node enlargement.
• Recurrent ulcers in unusual sites (hard palate, attached gum) which are less typical for aphthous origin.
• Multiple severe ulcers with systemic symptoms (fever, malaise, GI issues): may indicate Crohn’s disease, coeliac disease, Behçet’s syndrome, or other systemic conditions.
• Ulcers with associated genital ulcers or eye inflammation: Behçet’s syndrome consideration.
• Persistent ulcers in children with growth issues: coeliac disease screening appropriate.

The realistic treatment ladder

Self-care for typical aphthous ulcers

• Gentle saltwater rinses 3–4 times daily.
• Avoid trigger foods during outbreaks.
• Topical anaesthetic gel (benzocaine, lidocaine) for pain before meals.
• OTC ulcer paste (e.g. Bonjela, Anbesol) for symptom relief.
• SLS-free toothpaste trial if recurrent.

Pharmacy and prescription topicals

• Triamcinolone in orabase (a topical steroid in adhesive paste): reduces inflammation and accelerates healing.
• Chlorhexidine mouthwash (0.2%): antimicrobial, prevents secondary infection.
• Hyaluronic acid topical gels (e.g. Gengigel): mucosal healing support.
• Tetracycline mouthwash (prescription): mild antimicrobial effect, sometimes used for major aphthous ulcers.

Systemic treatment for severe recurrent cases

• Vitamin and mineral repletion if deficiencies confirmed.
• Short courses of oral steroids for major aphthous ulcers.
• Colchicine, dapsone, or thalidomide in refractory cases (specialist territory).
• Investigation and treatment of underlying systemic disease.

What does not help

• Antibiotics for typical aphthous ulcers (no infection to treat).
• Antiviral medication (most ulcers are not herpes).
• Aggressive cauterisation or chemical burning (may worsen and scar).
• “Ulcer toothpastes” with no active ingredient beyond placebo.

The cancer concern, addressed honestly

Oral cancer accounts for around 8,300 new cases annually in the UK and 2,700 deaths. Risk factors include smoking, alcohol consumption, HPV infection, and sun exposure (lip cancer specifically). Survival rates are dramatically better with early diagnosis (5-year survival around 80% for stage 1, dropping to 20–40% for advanced disease).

The 3-week ulcer rule is the practical screening tool. Any oral ulcer that has not healed in 3 weeks should be assessed by a dentist or GP. The vast majority turn out to be benign — but the few that are not benefit enormously from early diagnosis.

For UK patients

NHS provision for ulcer assessment is straightforward — your dentist or GP can examine and refer to oral medicine specialist if persistence or unusual features warrant. The 2-week wait pathway exists for suspected oral cancer; this is the appropriate route when concerning features are present. Most ulcers do not need specialist input.

Frequently asked questions

How long should a mouth ulcer last?

Typical minor aphthous ulcers heal in 7–14 days. Major aphthous ulcers can last 2–6 weeks. Any ulcer that has not healed in 3 weeks should be assessed by a dentist or GP — this is the standard NHS screening rule for oral cancer.

Are mouth ulcers contagious?

Aphthous ulcers (the common type) are not contagious — they are not caused by infectious organisms. Cold sores caused by herpes simplex virus are different and contagious; they appear typically on the lips rather than inside the mouth and have a vesicle stage before ulcerating.

Why do I keep getting recurrent ulcers?

Common contributors are stress, dietary triggers, sodium lauryl sulphate in toothpaste, vitamin deficiencies (B12, folate, iron), hormonal changes, and underlying systemic conditions. A blood test for nutritional status and a trial of SLS-free toothpaste are reasonable first steps. Persistent severe recurrence warrants oral medicine specialist assessment.

Should I get tested for vitamin deficiency if I have ulcers?

If recurrent (more than 3–4 episodes per year) or severe, yes. B12, folate, iron, ferritin, and zinc are the standard panel. Treating identified deficiencies can substantially reduce ulcer frequency in patients with this contribution.