OLP is regarded as a multifactorial pathology with a plethora of triggering and exacerbating agents, including drugs (angiotensin-converting enzyme inhibitors, non-steroidal anti-inflammatory drugs), dental restorative materials (amalgam, composite resins), psychological stress, trauma (Koebner’s phenomenon), nutritional deficiencies (iron, B12, vitamin A, C, D, E, and B12 deficiency), viruses (hepatitis C virus, Epstein-Barr virus, varicella zoster virus), and genetic polymorphisms. The gene discussed is ACE; the disease is nutritional deficiency disease.