A primary disorder of the skin resulting in violaceous, polygonal, flat skin lesions that often pruritic (itchy). Seen commonly on the wrists, shins, lower back and genitalia. Involvement of the scalp may lead to hair loss. The cause of lichen planus is unknown, but may occur after the use of a drug (thiazide diuretics, phenothiazines, antimalarials). Treatment with topical corticosteroids is common. In most patients, spontaneous regression of the disease will be seen 6 months to 2 years after onset. Lichen planus (LP) is a disease of the skin and/or mucous membranes that resembles lichen. It is thought to be the result of an autoimmune process with an unknown initial trigger. Where the trigger is known, the term lichenoid lesion is used instead. There is no cure, but many different medications and procedures have been used to control the symptoms. An OSH glossary used in safety and health at work which is, adopted by ILO {102}. The term definition has been obtained from the secondary source