Few people have never had a sore in their mouth. Scald it on hot soup or bite the inside of your cheek and it throbs for a few days before healing without your noticing. That is why mouth sores are easy to brush off, and it is precisely that familiarity that makes one signal easy to miss: a sore that, unlike usual, simply will not heal and lingers. Fortunately, because oral cancer arises in the mouth, it sits in a place easy to inspect with your eyes, so with just a little ongoing attention there is a good chance of catching it early.
The most widely used threshold is 'two weeks.' Common aphthous ulcers and bite injuries usually heal within one to two weeks. But if a mouth ulcer that appeared for no clear reason stays unchanged or even grows over more than two weeks, it is worth being seen. The absence of pain is no reason to relax, either. Early oral cancer is often painless, so it is easy to let time slip by, thinking it must be fine since it does not hurt.
Shape and color offer clues, too. If a white patch (leukoplakia) or a red patch (erythroplakia) that does not rub or peel off appears on the lining of the mouth and will not go away, it deserves a careful look. Red patches in particular are known to carry a higher chance of change than white ones. A lump that feels firmer than the surrounding tissue when touched, and unexplained bleeding that keeps coming from a spot that will not heal, are also best not ignored.
You can do a self-check calmly in front of a mirror in good light. First turn the lips out and look inside and out, then follow along the upper and lower gums. Stick out your tongue and look at the top, bottom, and both sides; the sides and underside of the tongue in particular are common sites for oral cancer, so check them thoroughly. Gently feel the inside of your cheeks with a finger to see whether there is any unusual lump or thickened area, and take a full turn around the roof of the mouth and the floor beneath the tongue. Making it a habit about once a month while brushing your teeth keeps it from being a burden.
Knowing the factors that raise the risk also helps. Smoking and drinking clearly increase the risk of oral cancer, and doing both together raises it further. An ill-fitting denture or a sharp tooth edge that keeps irritating the same spot, and habits such as chewing tobacco or betel nut enjoyed in some regions, are also counted as risk factors. If any of these apply to you, checking yourself more often brings peace of mind.
It helps to remember that a self-check is, at most, a habit for noticing warning signs early, not a tool for making a diagnosis. Finding a suspicious spot does not mean it is cancer, but if you have a sore that crosses the two-week rule, a patch that will not disappear, or a firm lump, the surest course is to have it confirmed at a dental clinic, an ear-nose-throat clinic, or an oral and maxillofacial surgery department. The earlier it is found, the easier the treatment.
This article shares general medical information in plain language and does not replace individual diagnosis or treatment. If you have any symptom that concerns you, please be sure to seek care at a medical facility.