What causes loss of taste and smell?

Anosmia: Taste is mostly dependent on the sense of smell. Loss of that sense is called anosmia. A very common cause is head trauma, due to shearing of the tiny nerves from the nose going into the brain through a perforated cribiform plate at the base of the skull. Sudden jarring can sever those nerves. There are other conditions and medications that can impair this sense, too.