White lines inside the cheek: is it lichen planus?

The inner surface of the cheek is one of the parts of the mouth most exposed to rubbing and biting; that is why white changes are common here. In a study in which 2,395 people were examined as part of the national mouth cancer screening programme in Slovenia, a change in the lining of the mouth was found in 27% of participants. Among the ten commonest findings were cheek-biting marks and the white line at the level where the teeth meet (linea alba), as well as lichen planus. So seeing something white in your cheek is not bad news in itself; what matters is the shape, position and behaviour of the white patch.

Oral lichen planus is a long-term condition that arises when the immune system turns on the cells of the layer lining the inside of the mouth. MSD Manuals describes its typical appearance in the mouth as lace-like, bluish-white lines and branches; these are called Wickham's striae. The NHS writes that white patches in the mouth are seen on the gums, the tongue or the inside of the cheeks. According to MSD, this type of mouth patch often causes no pain, and the person may not know it is there. It can also be seen in the mouth alone, without the skin being involved. The condition is not contagious.

Lichen planus appears in two main forms. In the net-like (reticular) type there are only white lines, and it usually causes no symptoms. In the erosive type, on the other hand, red, thinned areas or shallow sores form between the lines; according to MSD, these sores can be painful and recurring and can make eating and drinking difficult. The NHS, too, lists a burning or stinging feeling in the mouth, especially when eating and drinking, among the symptoms. When the gums are involved, they can look red and peeling and hurt when brushed. Both types can be seen together in the same person, or turn into one another from time to time; MSD writes that flare-ups and quiet periods are common.

How common is it? In a meta-analysis published in JAMA Dermatology that combined 46 studies, the frequency of oral lichen planus in the general population was calculated at 0.89%; but the confidence interval ran from 0.38% to 2.05%, meaning the true rate could be half this or twice this. It was more common in women than in men, and at 40 and over than in younger people: in the five clinical studies with age data, 0.62% under 40 and 1.90% at 40 and over. The authors stress that the differences between studies are large and that the figures should be interpreted with care. MSD states that up to 60% of women with lichen planus in the mouth may also have unnoticed lichen planus in the genital area.

There is a condition that resembles lichen planus but has a known cause: a lichenoid reaction. The cause is usually a medicine or a filling material in the mouth. MSD lists beta blockers, anti-inflammatory painkillers (NSAIDs), some blood pressure medicines (ACE inhibitors), some diabetes medicines (sulfonylureas), antimalarials, penicillamine and thiazide-type diuretics among the medicines that can trigger lichen planus. With a reaction to amalgam (silver-coloured) fillings, the white patch is typically seen in the area of the cheek that the filling touches directly, often on one side. In a 2026 meta-analysis combining 365 patients in 11 studies, replacing the amalgam filling with another material markedly increased the likelihood of the lesion healing; the benefit was greater in patients whose lesion touched the filling directly and whose patch test was positive. The authors also note that there were signs of publication bias and that the certainty of the evidence was moderate.

Three simple observations you can make at home roughly tell these conditions apart. The first is the stretch test: stretch your cheek outwards with your finger. According to a case report from the Netherlands, the milky white, greyish appearance called leukoedema almost completely disappears when the cheek is stretched, and it is a normal variation; no biopsy or treatment is needed. The lines of lichen planus do not disappear when stretched. The second is the wipe test: try gently wiping the white area with a clean piece of gauze. According to the NHS, with oral thrush the white patches come off when wiped, leaving red spots underneath that may bleed; leukoplakia, on the other hand, does not come off when wiped or scraped. The third is position and pattern: white running only along the level where the teeth meet, rough or peeling, suggests a friction and biting mark, while a symmetrical lace pattern in both cheeks suggests lichen planus.

The question of cancer risk is the one people most want answered, and the honest answer has two sides. In a meta-analysis combining 38,083 patients in 101 studies, the rate at which oral lichen planus turned into cancer was 1.43%; in lichen planus with epithelial dysplasia (disordered cell structure), this rate rose to 5.13%. Smoking and alcohol use, the lesion being on the tongue, the red and erosive type, and hepatitis C infection were factors that increased the risk. In another meta-analysis that applied the diagnostic criteria very strictly, however, the rate in 12,838 patients fell to 0.44%; these authors argue that the reported rates are exaggerated. The shared message of the two studies is the same: the risk is low but not zero, and that is why there is follow-up.

There is also a link between lichen planus and hepatitis C. MSD writes that lichen planus in the mouth can be seen together with hepatitis B, hepatitis B vaccination, hepatitis C and primary biliary cholangitis, a liver disease, and that liver tests and tests for hepatitis B and C may be done after diagnosis. In the meta-analysis of 38,083 patients, hepatitis C infection was among the factors that increased the risk of turning into cancer. So if you have been diagnosed with lichen planus, it is a fair question to ask your doctor whether these tests are needed in your case.

The first list is the typical behaviour of harmless or quiet conditions; even so, these should be shown to your dentist once. If a single item from the second list applies to you, do not put off the appointment.

Diagnosing a white patch in the cheek usually starts with looking, but does not end there. The order is as follows.

1. 1

   History and list of medicines

   You are asked how long the white patch has been there, whether it causes pain or burning, about smoking and alcohol, and about cheek-biting and teeth-clenching habits. Take a list of all the medicines you use; MSD lists some blood pressure, pain and diabetes medicines among the causes of a lichenoid reaction.

2. 2

   Examination of the whole mouth and the skin

   Both cheeks, the sides of the tongue, the gums and the palate are examined together, and the clinician looks at whether the lines are symmetrical. Skin findings such as purplish-red bumps on the wrists, thinning and ridging of the nails, or areas of hair loss on the scalp also support the diagnosis if present.

3. 3

   Stretching and wiping

   Leukoedema is told apart by stretching the cheek, and thrush by wiping the white area. Whether the white patch touches a filling, and what the filling is made of, are noted.

4. 4

   Biopsy

   MSD writes that because there are other conditions in the mouth that resemble lichen planus (such as thrush and leukoplakia), the diagnosis is usually confirmed by biopsy. A small piece is taken from the numbed area and examined under the microscope; this examination also shows whether there is dysplasia.

5. 5

   Blood tests and patch testing

   After diagnosis, the doctor may request liver tests and tests for hepatitis B and C. If the white patch touches an amalgam filling, a patch test looking for an allergy to the filling material may be considered.

6. 6

   Follow-up plan

   Once diagnosed, the condition is not a file that is closed in one go. Your clinician decides the interval between check-ups according to the type of lesion, whether there is dysplasia and your risk factors; ask about this interval clearly and write it down.

There is no single treatment for a white patch in the cheek; what is done depends on the diagnosis.

The following are wrong decisions often seen with this complaint. We set them out so that, whichever clinician you see, you can ask the right questions.

The timescales vary widely depending on the diagnosis. The sequence below is for diagnosed oral lichen planus; the plan of the clinician following you takes priority.

1. The first weeks after diagnosis

   If there is burning, the NHS recommends cutting down on salty, spicy and acidic food, switching to an alcohol-free mouthwash and brushing your teeth carefully twice a day. The prescribed local treatment begins.

2. Over the months

   Erosive areas can calm down with treatment, but the white lines often stay. This does not mean the treatment has failed; the goal is a mouth without pain or sores.

3. Over the years

   The NHS writes that lichen planus in the mouth can last several years; MSD states that flare-ups and quiet periods are common. Check-ups continue through all of these periods.

We do not give a single figure here, because behind a white patch in the cheek there may be a variation that needs no procedure at all, or lichen planus that calls for a biopsy and long follow-up. These are the items that determine the scope:

How the diagnosis is made clear

Some conditions are told apart by examination; if lichen planus or leukoplakia is suspected, a biopsy and pathology examination are needed.

Whether there are symptoms

With the type that causes no symptoms, watching alone is enough; with the erosive type, medicine and more frequent check-ups may be needed.

Further tests

Hepatitis and liver tests, or a patch test, go into the plan as the clinician decides.

Filling or tooth corrections

Replacing a filling that touches the white patch or smoothing sharp tooth edges are separate items.