Dra. Cléo Salustiano In this article
SummaryCanker sore, herpes, bump or red spot: how to tell them apartWhat helps, what to avoid and when to seek careFAQRead nextCanker Sore on the Gums: What It Is, How Long It Lasts and Herpes vs. Canker Sore
Quick summary of this article+
A canker sore on the gums is a shallow ulcer with a white or yellowish base and a red halo that hurts when eating and brushing and usually heals on its own in one to two weeks. It is not contagious and prefers the looser lining of the mouth, while herpes appears as clustered blisters, more often on the firm gum and the roof of the mouth, and is contagious. A pus-filled bump near a tooth may be a fistula from an infection and needs treatment. A soft brush and gentle foods help; aspirin on the gum, alcohol and home cauterizing should be avoided. A sore lasting over two weeks needs an exam, and fever or spreading swelling calls for the emergency room. In Mooca, Dr. Cléo Salustiano (CRO-SP 170844) sees patients every day, from 8 a.m. to 10 p.m.
A canker sore on the gums is a small round or oval ulcer with a white or yellowish center and a red border, which hurts mainly when eating and brushing. Most of the time, it heals on its own in about one to two weeks and is not contagious. What calls for an assessment is a sore that does not heal within two weeks, keeps coming back, is very large, comes with fever or shows up as a pus-filled bump near a tooth, because then the cause may be something else, such as herpes, an abscess or another lesion.
At the office, many people call any mouth sore a "canker sore". But the gums can also have herpes, toothbrush injuries, bumps from a tooth infection and red spots from inflammation, and each one needs a different approach. Looking at where the lesion is, how it started and how long it lasts helps a lot to tell them apart.
Dr. Cléo Salustiano (CRO-SP 170844), a dentist in Mooca, explains what causes canker sores on the gums, how to tell them apart from herpes and other bumps, what helps at home, what to avoid and when to seek care.
This article comes from Dr. Cléo Salustiano's dental office in Mooca, São Paulo (care in English, Portuguese and Spanish). See the gum health page to learn how the treatment is done here and book your assessment.
Canker sore, herpes, bump or red spot: how to tell them apart
Canker sore (aphthous ulcer): it starts as a sore area and soon becomes a shallow ulcer with a white or yellowish base and a red halo. It usually appears on the looser lining of the mouth, such as the fold between the gum and the lip or cheek, the inside of the lips and the sides of the tongue. The causes are not fully understood; common triggers include minor injuries (toothbrush, bites, braces), stress, hormonal changes, some foods and, in some people, certain toothpastes. Canker sores do not spread from person to person.
Oral herpes: it usually starts with tingling or burning, followed by a cluster of small blisters that burst and turn into small sores. Inside the mouth, it appears more often on the firm gum attached to the teeth and on the roof of the mouth, while canker sores prefer the looser lining. Herpes is contagious, especially during the blister stage. In children, the first infection may come with fever, very swollen gums and difficulty eating, and needs to be assessed.
Bump on the gums: when it sits near the root of a tooth, sometimes releases pus or a bad taste and comes and goes, it may be a fistula, which is the drainage path of an infection in the tooth or gum. It often does not hurt, but it will not go away for good unless the cause is treated. See tooth abscess: what to do. Other firm, painless bumps may be benign growths or bony bumps, which the dentist assesses.
Red spot on the gums: it may be inflammation from plaque (gingivitis), a small injury from brushing or flossing, or a small bleed under the gum surface. During pregnancy, the gum can form a reddish lump that bleeds easily. If the spot disappears within a few days with good hygiene, it is usually a minor injury or mild inflammation; if it persists, grows or bleeds a lot, it should be examined. The article swollen gums: what to do explains gum inflammation.
| Lesion | What it usually looks like | What to do |
|---|---|---|
| Canker sore | Shallow ulcer, white or yellowish base, red halo, on the looser lining | Local care; get it checked if it lasts over two weeks |
| Herpes | Clustered blisters that become sores, on firm gum or roof of the mouth; contagious | Avoid contact; get assessed, especially with fever |
| Fistula (pus bump) | Bump near a root, with pus or bad taste, that comes and goes | Assessment to treat the tooth or gum infection |
| Red spot | Inflammation, minor injury or small bleed | Careful hygiene; get it checked if it persists |
| Sore that does not heal | Lesion lasting more than two weeks | Examination by a dentist |
What helps, what to avoid and when to seek care
While the canker sore heals, it helps to brush with a soft toothbrush, carefully around the area; avoid acidic, very salty, spicy or crunchy foods that irritate the sore; prefer cold or lukewarm, soft foods; and keep your mouth clean, because plaque worsens inflammation. A gentle rinse with warm water and a little salt can make the area more comfortable. Protective gels and topical anesthetics sold at pharmacies should only be used as advised by a doctor, dentist or pharmacist and according to the label, and the same goes for pain relievers.
What to avoid: placing an aspirin tablet on the sore or gum, because it causes a chemical burn; rinsing with or applying alcohol, lemon, vinegar or undiluted baking soda to the sore; trying to "cauterize" the sore at home with any product; and popping or squeezing bumps on the gums. These remedies can make the lesion bigger, delay healing and hide signs of infection.
See a dentist if the sore does not heal within two weeks, if the sores are very large, many at once or keep coming back very often, if there is a pus-filled bump near a tooth, or if eating and drinking become difficult. Frequently recurring canker sores may be linked to nutritional deficiencies or general health conditions, and the dentist can guide further investigation with your doctor. Fever, swelling of the face or neck that is spreading, or difficulty swallowing or breathing require immediate care at an emergency room.
This content is for information only and does not replace an exam. Consult a dentist whenever a sore on the gums does not improve or comes with other symptoms. In Mooca, Dr. Cléo Salustiano sees patients every day, from 8 a.m. to 10 p.m., including Sundays and holidays, for gum health and dental emergencies in Mooca.
How long does a canker sore on the gums last?
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Most small canker sores heal on their own in about one to two weeks, and the pain usually eases in the first few days. Larger sores can take longer. If the sore has not healed within two weeks, see a dentist.
How can I tell a canker sore from herpes?
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A canker sore is usually a single sore or a few, shallow, with a white base and red halo, on the looser lining of the mouth. Herpes starts with tingling and clustered blisters that burst, and appears more on the firm gum and the roof of the mouth. If in doubt, the dentist can examine it.
What is a bump on the gums?
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It depends on where it is and what it looks like. A bump near a root, with pus or a bad taste, may be a fistula from a tooth or gum infection. Firm, painless bumps may be benign growths or bony bumps. Any bump that persists should be assessed.
What could a red spot on the gums be?
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It may be inflammation from plaque, a small injury from brushing or flossing, or a small bleed. With good hygiene, it usually disappears within a few days. If it persists, grows or bleeds a lot, book an exam.
Is a canker sore on the gums contagious?
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No. Canker sores do not spread from person to person. Herpes, however, is contagious, especially during the blister stage, so it is important to tell the two apart and avoid direct contact while herpes sores are present.
Can I put aspirin or baking soda on a canker sore?
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It is not recommended. Aspirin on the gum causes a chemical burn, and products such as alcohol, lemon, vinegar or undiluted baking soda can make the sore bigger. For relief, use a soft brush, gentle foods and pharmacy products only as advised by a professional and according to the label.
Where can I have a gum sore checked in Mooca?
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In Mooca, Dr. Cléo Salustiano (CRO-SP 170844) sees patients at Rua Hipódromo, 1141, near Bresser-Mooca station, Monday to Sunday, from 8 a.m. to 10 p.m., including holidays. Appointments via WhatsApp (11) 97409-7834, in Portuguese, English or Spanish.
