Lichen planus is a disease in which there is an itchy, swollen rash on the skin or in the mouth.

The exact cause of lichen planus is unknown. However, it is likely to be related to an allergic or immune reaction.

Risks include:

• Exposure to medications, dyes, and other chemical substances (including gold, antibiotics, arsenic, iodides, chloroquine, quinacrine, quinide, phenothiazines, and diuretics)
• Disorders such as hepatitis C

Lichen planus generally affects middle-aged adults. It is less common in children.

• Mouth lesions
  • Tender or painful (mild cases may have no discomfort)
  • Located on the sides of the tongue or the inside of the cheek
  • Occasionally located on the gums
  • Poorly defined area of blue-white spots or "pimples"
  • Lines of lesions that form a lacy-looking network
  • Gradual increase in size of the affected area
  • Lesions occasionally form painful ulcers
• Skin lesions:
  • Usually located on the inner wrist, legs, torso, or genitals
  • Itchy
  • Symmetrical
  • Single lesion or clusters of lesions, often at sites of skin trauma
  • Papule 2 - 4 cm in size
  • Papules clustered into a large, flat-topped lesion
  • Lesions have distinct, sharp borders
  • Possibly covered with fine white streaks or scratch marks called Wickham's striae
  • Shiny or scaly appearance
  • Dark colored -- reddish-purple (skin) or gray-white (mouth)
  • Possibility of developing blisters or ulcers

Other symptoms include:

• Dry mouth
• Hair loss
• Metallic taste in the mouth
• Ridges in the nails (nail abnormalities)

The health care provider may make the diagnosis based on the appearance of the skin or mouth lesions.

A skin lesion biopsy or biopsy of a mouth lesion can confirm the diagnosis. Blood tests may be done to rule out hepatitis.

The goal of treatment is to reduce your symptoms and speed healing of the skin lesions. If symptoms are mild, you may not need treatment.

Treatments may include:

• Antihistamines
• Immune-suppressing medications, such as cyclosporine (in severe cases)
• Lidocaine mouth washes -- to numb the area temporarily and make eating more comfortable (for mouth lesions)
• Topical corticosteroids (such as clobetasol) or oral corticosteroids (such as prednisone) -- to reduce inflammation and suppress immune responses. Corticosteroids may be injected directly into a lesion.
• Topical retinoic acid cream (a form of vitamin A) and other ointments or creams -- to reduce itching and inflammation and aid healing
• Dressings may be placed over topical medications to protect the skin from scratching.
• Ultraviolet light therapy may be helpful in some cases.

Lichen planus is generally not harmful and may get better with treatment. However it may last for weeks to months, and may come and go for years. It usually clears up within 18 months.

Long-standing mouth ulcers may develop into oral cancer.

Call your health care provider if:

• Your symptoms continue
• The skin or mouth lesions change in appearance
• The condition continues or worsens even with treatment
• Your dentist recommends adjusting your medications or treating conditions that trigger the disorder