Loss of the sense of smell. Do not confuse this term with, insomnia, which is loss of sleep. Hyposmia is a diminished (lowered) sense of smell. Anosmia can be considered complete hyposmia. Dysosmia is a distorted sense of smell. Additional Info: Anosmia can be temporary or permanenent and can be induced by chemical exposure, head or brain injury, illness and other factors. Although it may at first glance appear to have no major impact or even some benefit in everyday life, anosmia means doing without the little joys of life - the scent of food, fresh air, fine wine etc. Anosmia can even be fatal. How? (1) Certain toxic chemicals have strong detectable odors at low levels. But at higher levels, these saturate your smell receptors ("olfactory fatigue") and you can no longer smell the material. See: MSDS Relevance below. (2) An anosmic person can not smell smoke in a burning building. (3) An anosmic person might not detect that the food he is eating is spoiled. In June of 2009, the US Food and Drug Administration issued a warning for people to stop using three versions of an over-the-counter (OTC) cold "remedy" called Zicam, which was reported to have caused over 130 cases of anosmia, some after just one dose. This incident highlights the need for FDA regulation of herbal supplements and other such (homeopathic) "remedies" that are not currently subject to any government oversight in the US. A preliminary study found that olfactory (smelling) loss brought on by upper respiratory infections can be lessened or reversed through the use of a glucocoricoid (steroid) medication (Archives of Otolaryngology - Head and Neck Surgery, 2009, 135(10), 1000-1004. DOI: 10.1001/archoto.2009.141). MSDS Relevance: If a substance can cause anosmia, do not rely on the odor to detect it! For example, hydrogen sulfide, H2S, has the distinctive odor of rotten eggs at or below 10 parts per million (ppm) in air, but most people can not detect it at higher concentrations. If you were exposed to an H2S leak and the concentration went above 10 ppm, you might be lulled into thinking that the leak had stopped because you could not smell it anymore. Unfortunately, H2S can be fatal at concentrations of several hundred ppm. Likewise, even the ethyl mercapatan odorant used in natural and propane gas can fade over time due to rust, air or water in the tanks, fuel lines, or pipelines. Even concrete can absorb odorant, so if one smells gas in a basement, turns off the source and leaves, he might think everything is OK when he returns and discovers the smell is gone (but not the gas) and BOOM. Even if you don't have anosmia, relying on odor alone can have fatal consequences. See: The last two links below for examples. See also: Acute Toxicity, Chronic Toxicity, Neurotoxin, Hyposmia