SymptomMouth & teeth
Mouth Sores: Causes, Types and Treatment
Mouth sores are painful or painless spots, ulcers, blisters or patches on the lips, gums, tongue, cheeks or roof of the mouth. Most are canker sores (aphthous ulcers), cold sores from the herpes virus, or small injuries from biting or braces, and heal within 1 to 2 weeks. A sore that lasts longer than 3 weeks, a white or red patch that will not rub off, or sores with fever and difficulty drinking need a doctor or dentist.
Also called: Mouth ulcers, oral ulcers, oral lesions, canker sores, stomatitis
At a glance
- What they are
- Ulcers, blisters or patches inside the mouth or on the lips.
- Most common types
- Canker sores, cold sores, injury ulcers, oral thrush.
- Usual healing time
- 1 to 2 weeks for canker sores and cold sores.
- Red flag
- A sore or patch lasting more than 3 weeks, especially in smokers or heavy drinkers.
- Treatment
- Salt-water rinses, numbing gels, avoiding irritants, antivirals or antifungals when needed.
When to get help
Call 911 or go to the ER
- Widespread mouth sores with blistering or peeling skin, red eyes or genital sores, especially after a new medicine (possible Stevens-Johnson syndrome)
- Mouth sores with difficulty breathing or swelling of the tongue or throat
See a doctor within a day or two
- A child or adult with painful mouth sores who cannot drink or has signs of dehydration (few wet diapers, no urine for 8 hours, dizziness)
- Mouth sores with high fever, or many sores on the gums in a young child (possible herpes gingivostomatitis)
- Mouth sores in someone on chemotherapy or with a weak immune system
- A cold sore near the eye or eye pain and redness
Book a routine appointment
- A mouth sore or ulcer that has not healed in 3 weeks
- A white or red patch that cannot be wiped off, or a lump in the mouth or on the lip
- Very frequent or very large canker sores, or sores with diarrhea, weight loss, genital sores or eye inflammation
- Sores from sharp teeth, dentures or braces that keep recurring
Usually safe to manage at home
- A single small canker sore that is healing within 2 weeks
- A cold sore on the lip in an otherwise healthy person
- A sore from biting your cheek or a burn from hot food
Types of mouth sores and how to tell them apart
| Type | Where | Appearance | Notes |
|---|---|---|---|
| Canker sore (aphthous ulcer) | Inside cheeks and lips, under tongue, soft palate | Round, white or yellow center with red halo | Not contagious; heals in 1 to 2 weeks |
| Cold sore (herpes simplex) | Lips and lip border; rarely gums or hard palate | Cluster of small blisters that crust | Contagious; tingling first |
| Traumatic ulcer | Where teeth, braces or dentures rub | Single ulcer, matches the irritation | Heals once the cause is removed |
| Oral thrush | Tongue, cheeks, palate | Creamy white patches that wipe off, leaving red areas | Babies, denture wearers, inhaled steroids, antibiotics |
| Hand, foot and mouth disease | Throughout mouth plus hands and feet | Small blisters and ulcers | Young children; fever |
| Herpangina | Back of the mouth and throat | Small blisters and ulcers | Children, summer; fever |
| Lichen planus | Inside cheeks, gums | Lacy white lines, sometimes red raw areas | Long-term; burning |
| Leukoplakia and erythroplakia | Anywhere | White or red patch that does not rub off | Can be precancerous |
| Oral cancer | Tongue sides, floor of mouth, lip | Persistent ulcer, lump or patch | Smokers, drinkers, HPV |
Common causes of mouth sores
Canker sores (aphthous ulcers)
Canker sores are the most common mouth ulcers. Minor ones are under 1 cm and heal in 7 to 14 days. Triggers include minor injury, stress, hormonal changes, certain foods (citrus, tomatoes, chocolate), toothpastes with sodium lauryl sulfate, and stopping smoking. Frequent canker sores can be linked to iron, vitamin B12 or folate deficiency, celiac disease or Crohn's disease.
Cold sores
Cold sores are caused by herpes simplex virus, usually HSV-1. After the first infection the virus stays dormant and reactivates with sunlight, colds, stress or menstruation. Tingling or burning on the lip comes first, then blisters that crust and heal in 7 to 10 days. They are contagious until fully crusted.
Injury and irritation
Biting your cheek or tongue, burns from hot food, sharp or broken teeth, new braces, ill-fitting dentures and aggressive brushing can all cause ulcers. They heal within 1 to 2 weeks once the cause is fixed.
Infections
- Oral thrush: a yeast infection common in babies, older adults with dentures, people using steroid inhalers without rinsing, and after antibiotics.
- Hand, foot and mouth disease: mouth sores with spots on hands and feet in young children.
- Primary herpes gingivostomatitis: a first herpes infection in young children, with fever, swollen red gums and many painful sores. Children may refuse to drink.
- Syphilis and HIV can cause mouth ulcers.
Medical conditions and medicines
- Behçet's disease: recurring mouth and genital ulcers with eye inflammation.
- Inflammatory bowel disease and celiac disease.
- Lichen planus and other autoimmune skin conditions.
- Chemotherapy and radiotherapy (mucositis).
- Medicines: NSAIDs, some blood pressure medicines, methotrexate and nicorandil.
- Low white blood cell counts.
Oral cancer
Oral cancer can start as an ulcer that does not heal, a red or white patch, or a lump. Risk is highest with smoking, chewing tobacco or betel nut, heavy alcohol use and HPV infection. Any sore lasting over 3 weeks should be seen by a dentist or doctor.
How mouth sores are diagnosed
Most are diagnosed by appearance and history. A dentist or doctor may:
- take a swab for herpes or thrush
- order blood tests for iron, vitamin B12, folate and celiac disease if canker sores are frequent
- take a biopsy of a sore or patch that has lasted more than 3 weeks
How to get rid of mouth sores
Home care
- Rinse with warm salt water (half a teaspoon of salt in a cup of warm water) several times a day.
- Use an over-the-counter numbing gel or protective paste on the sore, following the label.
- Avoid triggers: spicy, acidic, salty or crunchy foods, and very hot drinks.
- Use a soft toothbrush and an SLS-free toothpaste.
- Take acetaminophen (paracetamol) or ibuprofen for pain, following the label dose. No aspirin for children or teenagers.
- Drink plenty of fluids. For children, cold drinks and ice pops help.
Medical treatments
- Canker sores: antimicrobial or steroid mouthwashes and pastes for frequent or severe sores. Correcting any deficiency.
- Cold sores: antiviral cream or tablets, most effective at the first tingle.
- Oral thrush: antifungal gel, drops or tablets.
- Lichen planus: steroid gels or mouthwashes.
- Ulcers from teeth or dentures: dental repair or adjustment.
Preventing mouth sores
- Protect your lips from sun with an SPF lip balm to reduce cold sores.
- Do not share cups or utensils, or kiss others, during a cold sore outbreak.
- Rinse your mouth after using steroid inhalers.
- Have dentures and braces adjusted if they rub.
- Avoid tobacco and limit alcohol.
- See a dentist regularly.
Frequently asked questions
What causes mouth sores?
The most common causes are canker sores, cold sores, injuries from biting or dental appliances, and thrush. Less often they come from viral infections like hand, foot and mouth disease, vitamin deficiencies, celiac or Crohn's disease, Behçet's disease, medicines or, rarely, oral cancer.
How long do mouth sores last?
Most canker sores and cold sores heal within 1 to 2 weeks. Injury-related sores heal once the cause is removed. A mouth sore lasting longer than 3 weeks should be checked by a dentist or doctor to rule out a more serious cause.
What is the difference between a canker sore and a cold sore?
Canker sores form inside the mouth, are not contagious and are round ulcers with a white center and red edge. Cold sores are caused by the herpes virus, usually appear on the outside of the lips as blister clusters, and are contagious.
When should I worry about a mouth sore?
Worry if a sore lasts more than 3 weeks, keeps getting bigger, is a white or red patch that will not rub off, bleeds easily, or comes with a lump in the neck, weight loss, or difficulty swallowing. Also seek help if pain stops you drinking.
Are mouth sores a sign of a vitamin deficiency?
Sometimes. Frequent canker sores can be associated with low iron, vitamin B12 or folate, as well as celiac disease. If you get recurring sores, ask your doctor for blood tests. Correcting a deficiency can reduce how often they occur.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Oral Medicine: Canker sores (aphthous ulcers)
- American Dental Association (MouthHealthy): Mouth sores
- NHS: Mouth ulcers
- MedlinePlus: Mouth sores
- National Institute of Dental and Craniofacial Research: Oral cancer
- CDC: Hand, foot, and mouth disease