Lichen planus: Causes

What causes lichen planus?

We still don’t know the exact cause. It’s thought that lichen planus develops when a person’s immune system mistakes a part of their body as foreign. When this happens, the person’s immune system attacks healthy cells in their body.

It’s not clear why the immune system attacks. When someone has lichen planus, it may be that an infection, which people often don’t know they have, provokes the immune system. This, in turn, causes the immune system to attack. More research is needed to know for sure.

While looking for the cause of lichen planus, researchers have discovered the following:

• Lichen planus can run in families. Some people may be more likely to develop this condition because it’s in their genes. There have been several reports of lichen planus running in families. We know that a rare type of lichen planus, called familial bullous lichen planus, runs in families.
  
  If blood relatives have lichen planus, it doesn’t guarantee that you’ll develop it. It means you have a greater likelihood of developing it.

• There may be a link between lichen planus and the hepatitis C virus. Some people with hepatitis C also have lichen planus. For this reason, your dermatologist may check to see whether you have this virus.

• Some medications can cause a rash that looks like lichen planus. These medications include diuretics (treatment for high blood pressure and heart disease), pain relievers, and medication taken to prevent malaria. That’s why it’s so important to tell your dermatologist about every medication that you take.

• In the mouth, a metal filling may be the cause. This is due to an allergic reaction. It’s rare, but it can happen. If this is the cause, replacing metal fillings with non-metal fillings may be an option. Be sure to discuss this option with your dermatologist and dentist.

Who gets lichen planus?

Anyone can get lichen planus. However, it seems most common in middle-aged adults. Few children develop lichen planus.

If you are concerned that you may have lichen planus, it’s important to find out. Some people need treatment to prevent the condition from worsening or to speed up healing. Treatment can also bring relief if symptoms bother you.

To find out how dermatologists diagnose and treat this condition, go to Lichen planus: Diagnosis and treatment.

References
Laeijendecker R, Dekker SK, et al. “Oral lichen planus and allergy to dental amalgam restorations.” Arch Dermatol. 2004 Dec;140(12):1434-8.

Pelet del Toro N, Strunk A, et al. “Prevalence and treatment patterns of lichen planus.” J Am Acad Dermatol. 2024 Nov 21:S0190-9622(24)03236-5. Epub ahead of print.

Shiohara T, Mizukawa Y. “Lichen planus and lichenoid dermatoses.” In: Bolognia JL, et al. Dermatology. (fourth edition). Mosby Elsevier, China, 2018: 188-90.

Tziotzios C, Lee JYW, et al. “Lichen planus and lichenoid dermatoses: Clinical overview and molecular basis.” J Am Acad Dermatol. 2018 Nov;79(5):789-804.

Written by:
Paula Ludmann, MS

Reviewed by:
DiAnne Davis, MD, FAAD
Elisa Gallo, MD, FAAD
William Warren Kwan, MD, FAAD
Shari Lipner, MD, PhD, FAAD

Last updated: 1/27/25