Anosmia: The failure of the development of or the loss of the sense of smell. Causes include conditions that damage nerve pathways that carry sensation from the nose to the brain. The most common causes are aging, nasal and/or sinus disease, prior viral upper respiratory tract infections, and head trauma.
Leopold, Donald. "Disorders of Taste and Smell." Medscape.com. Jan. 15, 2016. <http://emedicine.medscape.com/article/861242-overview>.