The tongue appears white or pale yellow and coated when the surface is colonised by bacteria or fungi, and dead cells become trapped between the small nodules on the tongue.

A coated tongue is not a disease and is not usually a sign of anything serious. It’s usually only temporary.

You can try gently brushing it with a tongue scraper and drinking plenty of water to help it improve.

However, sometimes a coated tongue can indicate an infection or more serious condition. You should see your GP for advice if:

• you’re concerned about changes to the appearance of your tongue
• your tongue hurts (read about the causes of tongue pain)
• your coated tongue persists for longer than two weeks

You can read on to learn more about the possible causes of a coated tongue, but do not use this to diagnose yourself with a condition – always leave that to your GP.

Note that in a minority of people, a coated tongue may never return to its normal colour or texture, even after treatment. 

Common causes of white plaques on the tongue

Leukoplakia

Leukoplakia is a common condition that results in a painless white patch in the mouth, which sometimes appears on the tongue.

This white patch seems to be the result of too many cells being produced from the lining of the mouth and a protein called keratin being deposited. Leukoplakia can develop when the tongue has been irritated, and is linked with drinking too much alcohol and also with smoking.

Although not usually dangerous, in a few cases leukoplakia turns cancerous, often many years or even decades after it first appears. It is important that your mouth is regularly examined by a dentist or doctor to ensure that any leukoplakia is not increasing in size or changing, or that new areas of leukoplakia are not developing. Read more about leukoplakia.

Your dentist or specialist will usually be able to tell the difference between a white tongue caused by leukoplakia and a coated tongue.

Oral lichen planus

Oral lichen planus (lichen planus of the mouth) is a long-term disorder of the immune system that causes white lacy streaks and white patches in the mouth, including on the tongue. 

Mild cases do not usually cause any pain or discomfort, although it can cause burning sensations and discomfort in the mouth, painful red gums and sore patches in the lining of the mouth.

The exact cause of oral lichen planus is unknown. It does not run in families and cannot be passed on to other people. 

Mild cases will not need any treatment. More severe cases can be managed with an antiseptic mouthwash plus steroid sprays or steroid tablets dissolved in water to make a mouth rinse.

Learn more about lichen planus.

Oral thrush

Oral thrush is a yeast infection in the mouth caused by a fungus. It can cause a burning sensation on the tongue as well as sore white plaques that can be scraped off (although it may sometimes appear as a red patch).

You are more likely to develop oral thrush if you:

• have recently taken antibiotics or steroid medication
• use steroid inhalers to control asthma 
• have diabetes
• have a weakened immune system
• wear dentures 

You should see your GP if you think you have oral thrush. If it is left untreated, the symptoms will persist and your mouth will continue to be uncomfortable. Treatment is with antifungal medicines.

Read more about oral thrush.

Syphilis

Syphilis is a bacterial infection usually caught by having sex with someone who is infected.

Syphilis can cause a small painless sore or ulcer on the tongue if caught from having oral sex. This appears from 10 days to 3 months after exposure to the infection. Treatment is with a single dose of penicillin.

If left untreated, syphilis may lead to white plaques on the tongue called syphilitic leukoplakia.

Read more about syphilis.