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Olfactory fatigue, also known as odor fatigue or olfactory adaptation, is the temporary, normal inability to distinguish a particular odor after a prolonged exposure to that airborne compound. For example, when entering a restaurant initially the odor of food is often perceived as being very strong, but after time the awareness of the odor normally fades to the point where the smell is not perceptible or is much weaker. After leaving the area of high odor, the sensitivity is restored with time. Perfume counters will often have containers of coffee beans which tend to "reset" olfaction. Anosmia is the permanent loss of the sense of smell, and is different from olfactory fatigue.
It is a term commonly used in wine tasting, where one loses the ability to smell and distinguish wine bouquet after sniffing at wine(s) continuously for an extended period of time. The term is also used in the study of indoor air quality, for example, in the perception of odors from people, tobacco, and cleaning agents.
Olfactory fatigue is an example of neural adaptation or sensory adaptation. The body becomes desensitized to stimuli to prevent the overloading of the nervous system, thus allowing it to respond to new stimuli that are ‘out of the ordinary’.
The sense of smell is considered to be one of the least developed senses humans possess.
Improving olfactory sense
Olfactometrical method and clinical studies
Sachs mentions the earliest reference as old as early nineteenth century. The primitive stages in curing the condition in humans were through the clinical experiments. The Ellsberg method was one of the first to determine the threshold value for odours substances. Till date olfactometry method proposed by him is known to be one of the best methods to stimulate the threshold of olfactory senses and determine the decaying of the senses once there has been a continuous supply of same smell.
Rejuvenation through coffee
One solution put forth to rejuvenate the olfactory sense from olfactory fatigue is the use of coffee beans. In their research, Yaser Dorri, Maryam Sabeghi and Biji T. Kurien hypothesized “that smelling coffee not only refreshes olfactory sensory receptors but also stimulates appetite. Our effort to smell coffee beans for about 3–4 min after cooking enabled our sensory smell to be refreshed and thereby increasing our appetite greatly” (2006). Current Theories of smell suggest that molecules which look identical may tend to smell different, which can be due to the chemical makeup of the molecules and potential aromas packed within the minute particles. This is often referred to as isomers of the same molecules.[dubious ] Yaser Dorri, suggest that unique molecular structure of the coffee odorants could be the reason of detachment of these potent aromas from food and attachment of these strong odorants to the olfactory senses.
- American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
- Building Indoor Environment
- Thermal comfort
- Odors chapter, Fundamentals volume of the ASHRAE Handbook, ASHRAE, Inc., Atlanta, GA, 2005