Why do I have brown spots on my tongue?

Start by working out whether the brown is on the tongue or in it.

• A brown coating covers a broad area, is usually thickest toward the back, and lightens when you scrape or brush. It is stain held in the film of bacteria and dead cells. If that is what you see, our guide to coated tongue covers it in detail.
• Brown spots are flat, separate patches or freckles. They keep their shape and color after cleaning because the pigment sits in the lining of the tongue.

The rest of this page deals with the second kind.

Physiologic (ethnic) pigmentation

Many people, particularly those with medium to dark skin, have patches of brown pigment in the mouth. On the tongue this often shows as brown tips on the small fungiform bumps near the tip and sides. A review of oral pigmentation published in PMC notes it tends to increase with age and needs no treatment.

Smoker's melanosis

Tobacco smoke stimulates pigment cells in the mouth. The same review reports smoker's melanosis in about 21.5-30% of smokers. It appears as multiple light brown to brown-black flat patches, most often on the front gums but sometimes on the tongue, and it usually fades slowly over months to years after stopping smoking.

Melanotic macule

This is the mouth's version of a freckle: a single flat, evenly colored tan to dark brown spot with a clear edge, usually smaller than 1 cm. It is benign. Inside the mouth, though, dentists often biopsy it once to be sure, because early melanoma can look similar.

Medicines

Drugs linked to brown, gray or blue-black mouth pigmentation include some antimalarials, hormones and oral contraceptives, minocycline, amiodarone, phenothiazines and some chemotherapy drugs. The timing usually gives it away: the color appears after starting the medicine and may fade after it is stopped.

Brown mouth spots are occasionally the first visible sign of something beyond the mouth:

• Addison's disease. When the adrenal glands do not make enough hormone, the body raises a hormone that also stimulates pigment. Patchy brown areas can appear across the inside of the mouth, often before skin darkening. The NHS lists extreme tiredness, weight loss, salt craving, dizziness on standing and darker skin patches as other symptoms. This needs blood tests and treatment from a doctor.
• Peutz-Jeghers syndrome. An inherited condition in which small dark freckle-like spots appear on and around the lips and inside the mouth in childhood. MedlinePlus explains it is linked to polyps in the gut and a higher lifetime cancer risk, so it is managed with regular screening.
• Laugier-Hunziker syndrome. A rare, harmless condition causing brown spots on the lips, cheeks and tongue in adulthood, sometimes with dark streaks in the nails. It is diagnosed only after other causes are excluded.

• If you smoke, stopping is the one change that can make smoking-related brown patches fade, and it lowers your oral cancer risk.
• Rinse with water after coffee, tea or red wine to reduce surface staining of the coating.
• Clean the top of the tongue daily so stain does not build up on top of any natural pigment and confuse the picture.
• Take a clear photo of the spot in daylight. Compare it every few weeks so you can tell your dentist whether it has changed.

There is no home remedy that lightens true pigment, and products claiming to "whiten" the tongue will not change it.

A dentist will ask how long the spot has been there, whether you smoke, which medicines you take and whether there are similar spots elsewhere (lips, gums, skin, nails). Many brown spots can be diagnosed on sight. If a single spot has no clear explanation, a quick biopsy under local anesthetic is the standard way to confirm it is harmless. If several new patches appear with general symptoms, you may be referred for blood tests, including adrenal hormone tests.