--- title: "Mouth sore? The common types and the signs to act on" description: "Canker sores and cold sores usually go away on their own. The common mouth sores, what causes each, and the signs that a dentist or doctor should look." canonical: https://oralbench.com/mouth-sores alternate_html: https://oralbench.com/mouth-sores language: en-US last_updated: 2026-09-27 type: guia --- # Sores inside the mouth: what kind it is and when to worry 1. [Home](https://oralbench.com/) 2. [Mouth & gums](https://oralbench.com/oral-health) 3. Sores inside the mouth: what kind it is and when to worry Canker sores, cold sores, thrush, leukoplakia: the common mouth sores have different causes and different next steps. This page sorts them out and flags the signs that shouldn't wait. By **OralBench editorial team**Updated September 27, 2026 ![Sores inside the mouth: what kind it is and when to worry](https://oralbench.com/img/guia-mouth-sores-640.webp) Short answer MedlinePlus lists cold sores, canker sores, thrush and leukoplakia among the common mouth problems, and dry mouth and cancer treatment can cause sores too. Canker sores and fever blisters typically "go away on their own in 1–2 weeks," according to the National Institute of Dental and Craniofacial Research (NIDCR). Canker sores have no known cause, cold sores come from the herpes simplex virus, and thrush is a yeast infection. NIDCR says a sore, lump or patch in your mouth that lasts more than two weeks is a reason to see a dentist or a doctor. ## Common mouth sores and what points to each MedlinePlus names cold sores, canker sores, thrush and leukoplakia among the common mouth problems. NIDCR adds two situations that bring sores with them: a dry mouth and cancer treatment. Type What you see Cause the sources give What the sources say to do Canker sore A round white or yellow sore with a red border, inside the lips or cheeks, on the gums or the tongue No known cause; possible triggers include a bite, stress, hormones, quitting smoking and low folic acid, iron or vitamin B12. Not contagious See a doctor if they keep coming back or make eating or drinking difficult Cold sore (fever blister) Small fluid-filled blisters, usually around the border of the lips The herpes simplex virus, usually type 1. Very contagious See a doctor if it lasts longer than a few weeks, you have a high fever, or your eye gets irritated Thrush White patches, redness or soreness The yeast Candida growing out of control, for example when you're sick or taking antibiotics Antifungal medicines "get rid of yeast infections in most people" Leukoplakia White patches on the cheeks, gums or tongue Excess cell growth; common in smokers A white or red patch that lasts more than two weeks needs a dentist or a doctor Sores from a dry mouth Mouth sores alongside a sticky, dry feeling in the mouth Too little saliva, often from medicines or from conditions such as Sjögren's disease, HIV/AIDS or diabetes See your dentist or doctor to find out why your mouth is dry Sores from cancer treatment Painful sores and ulcers during or after chemotherapy or head and neck radiation The treatment kills fast-growing cells, including the ones that line the mouth "Call your healthcare provider if your mouth hurts." MedlinePlus (National Library of Medicine) health topics "Mouth Disorders", "Canker Sores", "Cold Sores" and "Yeast Infections"; NIDCR (NIH) pages "Fever Blisters & Canker Sores", "Dry Mouth", "Cancer Treatments and Oral Health" and "Oral Cancer"; CDC, "Candidiasis Basics". All read on September 27, 2026. ## White sores, gum sores and blisters A white sore usually means one of a few things. A round, painful sore with a white or yellow center and a red border is the canker sore pattern. A white patch rather than a sore points elsewhere: thrush, which CDC describes as "white patches, redness or soreness," or leukoplakia, which MedlinePlus calls "white patches of excess cell growth on the cheeks, gums or tongue, common in smokers." NIDCR's oral cancer page puts "a white or red patch in your mouth" on its list of signs that shouldn't last more than two weeks. Gums have several suspects. Canker sores can form on the gums, MedlinePlus says cold sores inside the mouth usually sit on the gums or the roof of the mouth, leukoplakia can show up there, and cancer treatment can leave the mouth and gums sore. Blisters on or around the lips point to a cold sore: NIDCR describes fever blisters as "painful fluid-filled sores that form on the outside of the mouth around the lips." Blisters spread across the inside of your mouth don't fit that picture or the canker sore one neatly, so let a doctor take a look, especially if you also have a fever. ## Can stress cause mouth sores? It can set off canker sores. NIDCR lists "emotional stress" among the possible triggers, and MedlinePlus says canker sores "may also be triggered by stress." NIDCR also notes that a dry mouth "can happen to anyone occasionally," for example "when nervous or stressed." It's a dry mouth that doesn't go away that brings the real trouble. If stress-linked sores keep coming back, you're in the "frequently recurring" case where NIDCR says to see a doctor. ## Signs a mouth sore shouldn't wait ### It's been two weeks A sore, lump or thick patch in your mouth, lip or throat that lasts more than two weeks needs a dentist or a doctor, per NIDCR. ### A patch, not a sore White or red patches in the mouth are on the same two-week list. ### Fever, or your eyes With a cold sore, NIDCR says to see a doctor for a high fever or eye irritation, or if it lasts longer than a few weeks. ### It keeps coming back Canker sores that recur often, or that make eating or drinking difficult, are a reason to see a doctor. ### Your immune system is weakened CDC says a weakened immune system raises the risk of candidiasis, and MedlinePlus says yeast infections can be harder to clear when your immune system is weak. ## Easing the pain, and what supplement pages promise Relief is much the same for most of these sores, and our canker sore page lists what NIDCR and MedlinePlus suggest, along with the FDA's caution about numbing products and children. If your mouth is dry, NIDCR adds sipping water, sugarless gum or hard candy, and a humidifier at night. The bonus guides from GumAktiv and DentiCore promise to "get rid of" canker sores, ulcers and candida as if they were one problem; the table above shows they aren't, and the canker sore page sets those promises against what the labels contain. ## Frequently asked questions **What causes sores in the mouth?** The common ones are canker sores (no known cause, with possible triggers like a bite or stress), cold sores (the herpes simplex virus) and thrush (a yeast infection). A dry mouth and cancer treatment can also cause mouth sores. **What is a mouth ulcer?** The term covers more than one thing. Canker sores, which NIDCR says are "also called aphthous ulcers," are one kind, and NIDCR lists mouth ulcers among the effects of chemotherapy. Like any mouth sore, one that lasts more than two weeks needs a dentist or a doctor. **Why do I have a white sore in my mouth?** A round sore with a white or yellow center and a red border is typical of a canker sore. White patches are different: they may be thrush or leukoplakia, and a white or red patch that lasts more than two weeks needs a dentist or a doctor. **How long do mouth sores last?** Canker sores and fever blisters typically go away on their own in 1 to 2 weeks, NIDCR says; MedlinePlus says cold sores normally go away "in a few weeks." A sore that lasts more than two weeks should be seen by a dentist or a doctor. **Is a sore on my gum serious?** It depends on what's behind it. Canker sores can form on the gums, and cold sores inside the mouth usually show up on the gums or the roof of the mouth. A white or red patch, or a sore that's still there after two weeks, needs a dentist. **Do vitamins help mouth sores?** A lack of folic acid, iron or vitamin B12 is one possible canker sore trigger. Our canker sore page covers that link and what the supplement labels on this site leave out. ## Related pages Mouth & gums ### [Canker sores: what sets them off and what eases them](https://oralbench.com/canker-sores) A canker sore, also called an aphthous ulcer, is a painful white or yellow sore with a red border that forms only inside the mouth, and it isn't contagious. Read more Mouth & gums ### [Cold sore or canker sore: which one is it, and does it spread?](https://oralbench.com/cold-sore-or-canker-sore) A cold sore (fever blister) comes from the herpes simplex virus and is very contagious; a canker sore isn't contagious at all. Read more Mouth & gums ### [Dry mouth: find the cause first, then the relief](https://oralbench.com/dry-mouth) Xerostomia is the technical term for dry mouth: not having enough saliva to keep your mouth wet. Read more Reviews ### [DentiCore review: a readable label with an odd sales pitch](https://oralbench.com/denticore) DentiCore isn't a probiotic. Read more Updated September 27, 2026. [See our full method](https://oralbench.com/how-we-choose) --- ## OralBench - OralBench, published by Grupo Marfre Automação e Tecnologia (Contagem, Brazil) - Email: contact@oralbench.com - Home: https://oralbench.com/ - llms.txt: https://oralbench.com/llms.txt · llms-full.txt: https://oralbench.com/llms-full.txt · sitemap: https://oralbench.com/sitemap.xml