What is oral lichen planus?

DermNet and Cleveland Clinic describe several forms, which often appear together:

• Reticular: the most common form. Fine white lines in a net or lace pattern, usually on both inner cheeks and sometimes on the tongue or gums. Often painless.
• Erosive (atrophic): red, inflamed, thinned areas, sometimes with open sores, often with white lines at the edges. Usually painful, especially with spicy, acidic, salty or crunchy food.
• Plaque type: solid white patches, more often seen in smokers, which can look like leukoplakia.

On the tongue it may show as white patches on the top surface or white lines along the sides. Unlike thrush, the white does not wipe off.

DermNet estimates lichen planus affects about 1-2% of adults, and about half of people with lichen planus on the skin also have it in the mouth. It is most common in adults over 45 and in women; Cleveland Clinic reports women are 3-4 times more likely to develop oral lichen planus.

The exact cause is unknown. The immune system attacks the cells lining the mouth. Things that can trigger or mimic it include:

• Medicines: a lichenoid drug reaction can follow some NSAIDs, blood pressure medicines, antimalarials and others
• Dental materials: contact reactions to amalgam (mercury), gold, nickel or acrylics, typically next to the filling
• Toothpaste flavors: particularly spearmint and cinnamon in some people
• Hepatitis C infection
• Stress and local injury, which can set off flares

Because plaque-type lichen planus and leukoplakia can look alike, a biopsy is often used to confirm the diagnosis and rule out precancerous change.

Reticular lichen planus that causes no symptoms may not need treatment beyond monitoring. For painful forms, a dentist or oral medicine specialist may use:

• Corticosteroids as gels, ointments, rinses or sprays applied to the mouth. Cleveland Clinic notes most people get major relief within a month of topical treatment.
• Calcineurin inhibitor ointments when steroids do not work
• Injections into a sore area or tablets for severe cases
• Removing a trigger, such as a dental material confirmed by patch testing, or a suspect medicine switched with the prescriber's agreement

DermNet notes it can clear within months or persist for years with flares and remissions. There is no permanent cure.

• Use a soft toothbrush and a mild, unflavored toothpaste without sodium lauryl sulfate, mint or cinnamon.
• Keep your teeth and gums very clean; DermNet lists meticulous oral hygiene among the usual measures.
• Avoid foods that sting: spicy, acidic, salty or crunchy foods and alcohol.
• Stop smoking.
• Be gentle with the tongue. Brushing or scraping over sore red areas can cause flares; clean only the parts that are comfortable.
• Do not stop prescribed medicines on your own if you suspect a drug reaction.

Cleveland Clinic states that about 1-4% of people with oral lichen planus develop oral cancer, with higher risk in the erosive form. DermNet describes the risk as rare but real. This is why regular check-ups are recommended even when you feel fine, and why any change should be reported promptly. Persistent ulcers or new lumps are usually biopsied.