LOSS OF SMELL
Loss of small, or anosmia, is a lack of functioning olfaction, or in other words, an inability to perceive odors. It can be either temporary or permanent. A related term, hyposmia, refers to decreased ability to smell, while hyperosmia refers to an increased 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, grape, garlic, vanilla and cinnamon.
A temporary loss of smell can be caused by obstruction of the nasal cavities by swelling or polyps or because of an infection. In contrast, 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 brain areas that process smell. The lack of the sense of smell at birth, usually due to genetic factors, is referred to as congenital anosmia. 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 damage to olfactory receptor neurons due to use of certain types of nasal spray such as zinc containing sprays.
Anosmia can have a number of detrimental effects. Patients with sudden onset anosmia may find food less appetizing, though congenital anosmics rarely complain about this. Loss of smell can also be dangerous because it hinders the detection of gas leaks, fire, and spoiled food. The common view of anosmia as trivial can make it more difficult for a patient to receive the same types of medical aid as someone who has lost other senses, such as hearing or sight. Losing an established and sentimental smell memory (e.g. the smell of grass, of the grandparents' attic, of a particular book, of loved ones, or of oneself) has been known to cause feelings of depression.