Lichen planus is an itchy skin rash that is thought to be an immune reaction to certain triggers, states MayoClinic. Though fairly common, the exact reason why it occurs is unknown. Symptoms include mouth sores, skin sores, dry mouth, hair loss, metallic taste and nail ridges.
Lichen planus is neither serious nor contagious, but some rare types are more serious and painful, explains MayoClinic. It can be diagnosed and confirmed through skin or mouth lesion biopsy. To rule out hepatitis, blood tests may also be done. Usual treatments are topical and oral medications to reduce symptoms. Drugs that weaken or suppress the immune system are another option.