It's also possible to get patches on the floor or roof of your mouth.
There are also a number of other causes of white patches on the tongue.
If you have leukoplakia, there's a small risk it could progress to mouth cancer over time.
This is why it's very important to see your dentist or GP if you have a white patch in your mouth.
Your dentist or GP will examine the patch and be able to rule out other possible causes like a fungal infection of the mouth (oral thrush) or cheek biting.
You may be referred to a specialist for a biopsy. A small piece of tissue from the patch will be removed and checked for abnormal cells.
Treatment for leukoplakia is not always needed, but you'll have regular check-ups to make sure the patch is not getting bigger.
The patch may get smaller or go away if you:
An operation is sometimes needed to remove the patch if there's a risk it could become cancerous.
The patch can be removed in a number of ways, including using a laser or a surgical scalpel. Your mouth should heal quickly afterwards.
In the UK, leukoplakia is mostly caused by smoking. But sometimes the exact cause is not known.
There are things you can do to reduce your risk of getting leukoplakia. These may also reduce your chances of getting mouth cancer.
Hairy leukoplakia is a type of leukoplakia caused by the Epstein-Barr virus.
It often affects people with a weakened immune system, particularly those with HIV and AIDS or who have had an organ transplant and are taking immunosuppressant medication.
It causes fuzzy white patches, often on the sides of the tongue, that look folded or ridged. They are not painful and cannot be brushed or scraped away.
Antiviral medications, or treatments applied directly to the patch, may be prescribed to treat hairy leukoplakia.
Unlike other types of leukoplakia, hairy leukoplakia does not carry a risk of mouth cancer.