Mouth Ulcers: Causes and When to Worry

Most mouth ulcers are harmless, either aphthous ulcers (canker sores) or small injuries from biting your cheek or a sharp tooth, and they heal on their own within one to two weeks. You should see a doctor or dentist if an ulcer lasts longer than three weeks, is unusually large, bleeds, keeps coming back, or appears with a red or white patch or a lump, and you should be especially careful if you smoke or chew tobacco, gutka, paan or areca nut.

Mouth ulcers are one of the most common reasons people in India reach for a gel from the chemist. Usually that is fine. But the mouth is also where one of India’s most common cancers starts, and an early cancer can look like an ordinary ulcer. This guide helps you tell the difference.

What are the common causes of mouth ulcers?

The NHS explains that most single mouth ulcers are caused by things you can try to avoid:

• Biting the inside of your cheek
• Badly fitting dentures, braces, rough fillings or a sharp tooth
• Cuts or burns from hard food or hot drinks
• Damage from a toothbrush or irritating toothpaste
• A food intolerance or allergy
• Feeling tired, stressed or anxious

Other triggers you cannot always control include hormonal changes such as pregnancy, your genes, deficiencies of iron, zinc, folic acid, vitamin B12 or vitamin D, and some medicines, including certain anti-inflammatory painkillers. The NHS also notes that some people develop mouth ulcers when they first stop smoking. This is temporary and not a reason to keep smoking.

What is an aphthous ulcer?

Aphthous ulcers are the most common type of ulcer inside the mouth. DermNet estimates that about 20 percent of people get them at least occasionally, often starting in childhood or the teenage years. Around 40 percent of people who get them have a family history.

They are typically round or oval, punched out sores with a white, yellow or grey base and a red halo, on the inside of the lips and cheeks or under the tongue. They can be very painful, especially with citrus fruit or spicy food. DermNet describes three types:

Type	How common	Size	Healing time
Minor aphthous ulcers	About 80 percent	Under 5 mm	1 to 2 weeks, no scar
Major aphthous ulcers	Less common	Often over 10 mm	Weeks to months, may scar
Herpetiform ulcers	Uncommon	Many pinpoint ulcers	Up to a month

Aphthous ulcers are not contagious. They are different from cold sores, which appear on or around the lips and often start with tingling. Our guide to cold sores explains the difference.

Which mouth ulcers need a doctor or dentist?

The NHS advises seeing a dentist or doctor if a mouth ulcer:

• Lasts longer than 3 weeks
• Is different from ulcers you have had before, for example bigger than usual or near the back of the throat
• Bleeds or becomes more painful and red, which may suggest infection

It also advises seeing a doctor if you have ulcers elsewhere on your body, such as the skin or genitals, or painful, red or swollen joints. Repeated mouth and genital ulcers together can point to conditions such as Behçet disease, which DermNet lists among the systemic causes of aphthous ulcers along with coeliac disease, Crohn disease and ulcerative colitis.

Warning signs of mouth cancer

The NHS lists these possible symptoms of mouth cancer:

• A mouth ulcer that lasts more than 3 weeks
• A red or white patch inside the mouth
• A lump inside the mouth or on the lip
• Pain in the mouth that does not go away
• Difficulty swallowing or speaking, or a hoarse voice
• A lump in the neck or throat
• Losing weight without trying

DermNet notes that early oral cancers are often painless and go unnoticed, which is why they are frequently found late. Most of these symptoms have harmless causes, but they should always be checked, because cancer found early may be easier to treat.

Why does tobacco use change the advice?

This is especially important in India. DermNet notes that oral cancer is particularly common in India, Pakistan and Bangladesh, and that in some parts of India it accounts for a large share of all cancers. The World Health Organization (WHO) lists tobacco, alcohol and areca nut (betel quid) use among the leading causes of oral cancer.

Risk factors include:

• Smoking cigarettes or bidis
• Chewing tobacco, gutka, khaini or paan with tobacco
• Chewing areca nut (supari), even without tobacco
• Regular alcohol use, which adds to the risk from tobacco

White patches inside the mouth called leukoplakia are linked to smoking, alcohol and betel quid chewing, and to oral submucous fibrosis. DermNet explains that some leukoplakia can turn out to be precancerous or cancerous, which is why a biopsy is needed to assess it.

If you use any of these products, do not wait three weeks to get a non healing sore, a white or red patch, or a stiff, burning mouth looked at. And it is never too late to stop. Doctors, dentists and tobacco cessation services can help.

How do I care for a simple mouth ulcer at home?

The NHS suggests:

Do

• Use a soft bristled toothbrush
• Drink cool drinks through a straw
• Eat softer foods
• Rinse with a warm salt water mouthwash and spit it out
• Eat a healthy, balanced diet and have regular dental check ups

Avoid

• Very spicy, salty or acidic food, including achaar and chutneys during a flare
• Rough, crunchy food
• Very hot or acidic drinks
• Toothpaste containing sodium lauryl sulphate, which DermNet also lists as a possible trigger

A pharmacist can suggest an antimicrobial mouthwash or a pain relieving gel. Avoid applying random creams, powders or home remedies such as alum or tobacco to an ulcer.

What will a doctor or dentist do?

They will look at the ulcer, check your teeth and fillings, and may feel your neck. Depending on the history, they may:

• Arrange blood tests for blood count, iron, vitamin B12 and folate if ulcers are frequent or severe
• Take a swab to look for thrush or a viral infection
• Take a small biopsy of a non healing ulcer or patch
• Prescribe a stronger mouthwash, gel or other treatment for severe or recurrent ulcers

Some skin conditions also affect the mouth. Oral lichen planus can cause white, lacy patches and sore erosions. Our guide to lichen planus explains more.

When are mouth sores an emergency?

Go to the nearest emergency department, or call 112 for emergencies or 108 for an ambulance, if mouth sores come with:

• A spreading rash, blisters or peeling skin
• Sore, red eyes or sores on the genitals
• Fever and feeling very unwell, especially after starting a new medicine in the past few weeks
• Swelling of the lips, tongue or throat, or difficulty breathing or swallowing

These can be signs of a serious drug reaction such as Stevens Johnson syndrome or a severe allergic reaction. Our guides to skin rash from medicines and skin red flags that need urgent care explain more.

When to see a dermatologist

See a dermatologist, dentist or doctor if:

• An ulcer has not healed in 3 weeks
• You get ulcers very often, or they are large and leave scars
• You also have ulcers on the genitals or skin, painful joints, eye symptoms or gut symptoms
• You have a white or red patch, a lump, or a burning, stiff mouth, especially if you use tobacco or areca nut
• You have skin rashes, hair loss or nail changes along with mouth sores

Most mouth ulcers are a short lived nuisance, but a few need prompt attention. For non urgent concerns, Dr. Maria offers online consultations and can advise whether you need an in person examination or a biopsy.