Lichen planus is a common disease that causes inflammation (swelling and irritation) on your skin or inside your mouth. On your skin, lichen planus causes a rash that is usually itchy. Inside your mouth, it may cause burning or soreness.

Lichen planus isn't a dangerous disease, and it usually goes away on its own. But in some people, it may come back. It's not contagious; you can't pass it on to others.

The cause of the inflammation that leads to lichen planus is not known, but it's been linked to:

• Hepatitis C, a virus that attacks your liver.
• Certain medicines, including some used to treat high blood pressure, diabetes, heart disease, and malaria. They can cause a medicine reaction that appears similar to lichen planus.
• Reactions to metal fillings in your teeth.
• An autoimmune reaction, meaning the body's own defense system, the immune system, attacks your mouth and skin cells by mistake.

Lichen planus usually affects men and women in middle age. Equal numbers of men and women get lichen planus of the skin. But women are twice as likely to get the disease inside the mouth. The disease is rare in people who are very young or very old.

Symptoms of lichen planus depend on the part or parts of your body affected. Common symptoms include:

• Skin. The most common symptom is shiny red or purple bumps. The bumps are firm and usually very itchy. You may have just a few or many of them. Fine white lines or scales may accompany the bumps. They can happen anywhere. But they are most common on your wrists, arms, back, and ankles. Thick, scaly patches may appear on your shins and ankles. Sometimes bumps on your skin may appear in an area where your skin has been scratched or burned. Dark skin patches may replace skin bumps that fade. The patches usually fade away after many months.
• Mouth. Lichen planus inside your mouth looks like lacy patches of tiny white dots. The patches may be on the inside of your cheeks or on your tongue. They may not cause any other symptoms. In severe cases, redness and sores develop.
• Nails. Lichen planus may appear on a few, or all, of your fingernails and toenails. Thinning, ridges, splitting, and nail loss are signs of the condition.
• Scalp. Redness, irritation, and tiny bumps can form on your scalp. In some cases, hair may start to thin and patches of hair loss may happen.
• Genitals. Lichen planus on your genitals can cause bright red, painful areas.

Your doctor or dentist may diagnose lichen planus based on the changes on your skin or in your mouth. To make sure of the diagnosis, you may need these tests:

• Blood test. This can rule out other causes of your symptoms.
• Skin biopsy. Your doctor will remove some skin cells and send them to a lab. There, they'll be examined under a microscope.

If your biopsy shows lichen planus and you have no symptoms, you probably don't need treatment. In most cases, lichen planus will go away within 2 years. If you have symptoms, such as severe itching or sores in your mouth or genital area, treatment can help. If you have lichen planus on your scalp, treatment is important to prevent permanent hair loss.

Lichen planus has no cure and will likely go away on its own over time. But treatment can help ease your symptoms and speed healing. Possible treatments are:

• Antihistamine medicine to relieve itching.
• Steroids on your skin or in your mouth to fight inflammation. (You may also take steroids in pill form for severe cases.)
• A type of ultraviolet light treatment called PUVA.
• Retinoic acid, a medicine derived from vitamin A and usually used for acne.
• Tacrolimus and pimecrolimus, ointments used for eczema.

Some evidence suggests that oral lichen planus may be an early warning for oral cancer. Make sure you see your dentist for an oral exam at least twice a year. Lichen planus near the genitals can lead to pain.

You can't do much to prevent lichen planus. But once you have it, you can take steps to keep it from getting worse:

• Don't injure your skin.
• Apply cool compresses instead of scratching.
• Limit the stress in your life.

If you have oral lichen planus, you can do the following:

• Stop smoking.
• Don't drink alcohol.
• Maintain good oral hygiene.
• Don't eat any foods that seem to irritate your mouth.
• Have a dental exam twice a year.

If you have any symptoms of lichen planus, talk with your doctor. You may need to see a dermatologist for the most effective care.

• Lichen planus is a common disease that causes inflammation (swelling and irritation) on your skin or inside your mouth.
• It's associated with hepatitis C, reaction to metal fillings, an autoimmune disorder, and certain medicines.
• The most common symptom is shiny red or purple bumps on the skin.
• Inside the mouth, lichen planus looks like lacy patches of tiny white dots.
• People with oral lichen planus should have dental exams twice a year.
• A physical exam and a biopsy can diagnose this disease.
• Treatment may include medicines like steroids or retinoic acid.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new directions your doctor gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose of that visit.
• Know how you can contact your doctor if you have questions.