What causes spots on the side of the tongue?

The sides of the tongue rest against the teeth all day. Every time you chew, talk or clench, they rub against tooth edges, fillings, braces or dentures. That makes them the natural place for bite marks, friction patches and ulcers. The sides toward the back also carry foliate papillae, a set of vertical folds with taste buds that can look like red ridges or lumps when they are irritated.

The same spot is also where thickened white patches and early cancers most often appear. A review in PMC notes that most tongue cancers arise on the lateral border of the front two-thirds of the tongue. So side-of-tongue spots deserve a slightly lower threshold for getting checked than spots on top.

Biting and sharp edges

A bite leaves a sore red or white mark that heals within one to two weeks. A broken tooth, rough filling or new orthodontic wire can cause a repeat sore in exactly the same spot. If a sore keeps reappearing where it touches a tooth, the tooth needs smoothing.

Canker sores

Small round ulcers with a white or yellow base and a red rim are common on the sides. They hurt, usually more than you would expect, and heal in 1-3 weeks.

Enlarged foliate papillae

These normal folds can swell after spicy food, infection or rubbing, and some people notice them for the first time and worry. They are on both sides, in the same position, and settle when the irritation stops.

Tooth indentations

A wavy edge with small pale or reddish dents matching your teeth is scalloped tongue, often from clenching, grinding or tongue swelling. It is not a spot disease, but it can look like a row of marks.

• Frictional keratosis: a rough white area where the tongue repeatedly rubs a tooth or appliance. It usually fades once the cause is fixed.
• Oral hairy leukoplakia: DermNet describes white, ridged or corrugated plaques on one or both sides of the tongue that do not wipe off. It is caused by Epstein-Barr virus, mostly in people with a weakened immune system, including HIV, and can be the first sign of HIV. It is not precancerous.
• Leukoplakia: a white patch that cannot be rubbed off and has no other explanation. Cleveland Clinic notes leukoplakia on the tongue or floor of the mouth is more likely to become cancerous than on the gums. See leukoplakia.
• Lichen planus: white lacy lines, often on the inside of the cheeks as well, sometimes with red sore areas. See oral lichen planus.
• Thrush: creamy patches that wipe off, leaving red spots.

• Run your tongue along your teeth: if you find a sharp edge next to the spot, book a dentist to smooth or repair it.
• Rinse with warm salt water and avoid spicy, acidic and crunchy food while it heals.
• If you clench or grind, notice it during the day and ask your dentist about a night guard.
• Avoid tobacco and limit alcohol; together they multiply the risk of mouth cancer, according to the American Cancer Society.
• Check the spot after 2 weeks. A healing sore should be clearly smaller.

A dentist will feel the area as well as look at it; firmness under a sore is an important sign. They will check your teeth for rough edges and look at the rest of your mouth. Patches without a clear cause are usually biopsied, and the NHS notes that a dentist can also help with ulcers, lumps, patches or pain in the mouth before you see a GP. Early tongue cancers found on the side are far easier to treat than late ones.