Olfactory fatigue, also known as odor fatigue, olfactory adaptation, and noseblindness, is the temporary, normal inability to distinguish a particular

odor An odor (American English) or odour (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is caused by one or more volatilized chemical compounds ...

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

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.

Anosmia Anosmia, also known as smell blindness, is the loss of the ability to detect one or more smells. Anosmia may be temporary or permanent. It differs from hyposmia, which is a decreased sensitivity to some or all smells. Anosmia can be due to a num ...

is the permanent loss of the sense of smell, and is different from olfactory fatigue. It is a term commonly used in

wine tasting Wine tasting is the sensory examination and evaluation of wine. While the practice of wine tasting is as ancient as its production, a more formalized methodology has slowly become established from the 14th century onward. Modern, professional w ...

, 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 Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduced ...

, for example, in the perception of odors from people,

tobacco Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...

, and cleaning agents. Since odor detection may be an indicator that exposure to certain chemicals is occurring, olfactory fatigue can also reduce one's awareness about

chemical hazard A chemical hazard is a (non-biological) substance that has the potential to cause harm to life or health. Chemicals are widely used in the home and in many other places. Exposure to chemicals can cause acute or long-term detrimental health eff ...

exposure. Olfactory fatigue is an example of

neural adaptation Neural adaptation or sensory adaptation is a gradual decrease over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if a hand is rested on a table, the ta ...

. 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'.

Mechanism

After olfactory neurons depolarize in response to an odorant, the G-protein mediated second messenger response activates adenylyl cyclase, increasing cyclic AMP (cAMP) concentration inside a cell, which then opens a cyclic nucleotide gated cation channel. The influx of Ca²⁺ ions through this channel triggers olfactory adaptation immediately because

Ca2+/calmodulin-dependent protein kinase II /calmodulin-dependent protein kinase II (CaM kinase II or CaMKII) is a serine/threonine-specific protein kinase that is regulated by the /calmodulin complex. CaMKII is involved in many signaling cascades and is thought to be an important mediator ...

or CaMK activation directly represses the opening of cation channels, inactivates adenylyl cyclase, and activates the

phosphodiesterase A phosphodiesterase (PDE) is an enzyme that breaks a phosphodiester bond. Usually, ''phosphodiesterase'' refers to cyclic nucleotide phosphodiesterases, which have great clinical significance and are described below. However, there are many oth ...

that cleaves cAMP. This series of actions by CaMK desensitizes olfactory receptors to prolonged odorant exposure. An ORN or an Olfactory Receptor Neuron alert goes off to detect the smell. When the nose is covered taste is a lot harder because the air we breathe goes into the mouth as well. A common idea is that vanilla smells sweet and that is because we taste sweet when we eat vanilla flavorings.

Mitigating scent effects on olfactory fatigue

According to a study by Grosofsky, Haupert and Versteeg, "fragrance sellers often provide coffee beans to their customers as a nasal palate cleanser" to reduce the effects of olfactory adaptation and habituation. In their study, participants sniffed coffee beans, lemon slices, or plain air. Participants then indicated which of four presented fragrances had not been previously smelled. The results indicated that coffee beans did not yield better performance than lemon slices or air.

References

External links

* {{cite journal , vauthors = Kristensen HK, Zilstorff-Pedersen K , title = Quantitative studies on the function of smell , journal = Acta Oto-Laryngologica , volume = 43 , issue = 6 , pages = 537–44 , date = December 1953 , pmid = 13138121 , doi = 10.3109/00016485309119884 Building biology Olfaction Wine tasting

Mechanism

Mitigating scent effects on olfactory fatigue

See also

References

External links