What Causes Lichen Planus?

Lichen planus is an "eruption of flat-topped, shiny, violaceous papules on flexor surfaces, male genitalia, and buccal mucosa of unknown cause; may form linear groups; microscopically characterized by a bandlike subepidermal lymphocytic infiltrate. Spontaneous resolution is common after months to years."

The word lichen refers to the lichen plant which grows on rocks or trees, while the word planus in Latin means "flat".

Lichen planus is an inflammatory skin condition, characterized by an itchy, non-infectious rash of small, polygonal (many sided) flat-topped pink or purple lesions (bumps) on the arms and legs. Other parts of the body may also be affected, including the mouth, nails, scalp, vulva, vagina, and penis. Involvement in the scalp can result in hair loss - sometimes permanent. 

According to the National Institutes of Health (NIH), USA, lichen planus affects between 1% and 2% of the American population. According to the National Health Service (NHS), UK, around 1 in every 50 people is affected by lichen planus. 

Nobody knows what the exact causes of lichen planus are. We know it can be triggered by taking certain medications, including thiazide diuretics, antimalarials and phenothiazines (a group of tranquilizing drugs with antipsychotic actions). A significant number of skin specialist doctors (dermatologists) believe it might be classified as an autoimmune disease. A higher-than-normal percentage of people with hepatitis C and some other liver diseases have lichen planus. 

Oral lichen planus is more common in women than in men. Skin lichen planus affects both sexes equally. It typically occurs in people over 30 years of age. About half of all affected people have oral lichen planus (symptoms in the inner surface of the mouth). Oral lichen planus typically occurs inside the cheeks, but may also affect the lips, gums and tongue.

Lichen planus:

• Does not appear to be an hereditary condition - you cannot pass it on to your children
• Is not an infectious condition - you cannot catch it from somebody with the condition
• Is not a form of cancer
• Occurrence does not seem to be linked to nutrition. However, spicy foods, citrus juices, and tomato products may aggravate symptoms if there are open sores in the mouth.