Toxic exogenous ligands such as TCDD enhance the degeneration of dopaminergic neurons in the midbrain owing to enhanced oxidative stress, thereby inducing experimental Parkinson’s disease; in contrast, several phytochemicals such as a flavonoid called tangeretin as well as natural compounds from the plant Withaferin sominifera act via AhR to protect against Parkinson’s symptoms in several models of this disease [235,236]. The gene discussed is AHR; the disease is Parkinson disease.