Anosmia

Anosmia is the lack of olfaction, or a loss of the sense of smell. It can be either temporary or permanent. A related term, hyponosmia refers to a decrease in the ability to smell. Some people may be anosmic for one particular odor. This is called "specific anosmia" and may be genetically based. Anosmia can be diagnosed by doctors by using scratch-n-sniff odor tests or by using commonly available odors such as coffee, lemon, and cinnamon.

A temporary loss of smell can be caused by a stuffy nose while a permanent loss of smell may be caused by death of olfactory receptor neurons in the nose, or by brain injury in which there is damage to the olfactory nerve or damage to the areas of brain itself that process smell (see olfactory system). Anosmia may be an early sign of degenerative brain diseases such as Parkinson's disease and Alzheimer's disease. Another specific cause of permanent loss could be from loss of olfactory receptor neurons due to use of zinc based nasal sprays. See here for an example.

Anosmia can have a number of detrimental effects on a person [1]. Patients with anosmia may find food less appetizing and life less appealing. This often leads to depression. Loss of smell can be dangerous also because it hinders the detection of gas leaks, fire, and rotten food.