Patients may experience reactions that are similar clinically and /or microscopically to lichen planus. These are called lichenoid reactions. The most common cause of lichenoid reactions is drugs.
A variety of systemic medications are known to induce these reactions and patients whose “lichen planus” developed following the administration of a new medication should consider the possibility that they are experiencing a lichenoid drug reaction.
Topically placed compounds, particularly those containing cinnamon, can produce similar reactions. Occasionally, but not often, dental restorative materials can produce lichenoid reactions.
Courtesy:Dr. John Wright