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“Smell”, from the “Allegory of the Senses” by Jan Brueghel the Elder , Museo del Prado
The domestic dog has one of the most sensitive olfactory organs

The smell ( lat. Olfactus , hence olfactory perception ) is the interpretation of the sensory excitations that are transmitted to the brain of an animal by the chemoreceptors of the nose or other olfactory organs . According to a recent study, humans should be able to differentiate between over a trillion odors.

In some areas of Switzerland the word Gout is also used for the smell , which also means taste and is related to the words gusto and goutieren .

Perception of smells

In mammals, the fragrances in the air reach the upper nasal cavity and the olfactory mucous membrane when they breathe in and more so when they smell (conscious feeling) . This is where the odor molecules are dissolved, making them chemically registerable for the cells. There are around 350 different types of receptors, each of which only responds to a specific group of scent molecules. The combination of the addressed receptors in the cells results in the odor mixture. Smelling - the sense of smell perception - depends on genetic and perceptual processes, the condition of the air and the learning ability of the brain .

Importance and diversity

Structural formula of the unpleasant smelling butyric acid

The sense of smell is essential for many animal species. For humans, the sense of smell is generally considered to be less important than seeing, hearing or touching, but its lack means a significant loss of quality of life.

The perceived smells or fragrances help living beings to identify food , spoilage (e.g. butyric acid as a sign of putrefaction , carrion odor, hydrogen sulphide from faeces), body odor of conspecifics (" stable odor ") and enemies, but also play a role in social behavior a major role. The sexual maturity or the mating behavior of female animals is the male animals mainly by pheromones signals (pheromones), and these are also suitable for communication and spatial orientation of an essential aids. Many animals set scent marks to mark out their territory or, like ants , follow the scent trail of their predecessors to the source of food. Most flowers emit fragrance to attract insects to pollinate. Pest control in fruit growing makes use of the effect of such pheromones, for example to limit the pairing of plum moths.

Smells can make you curious and are often associated with feelings, but emotions can also evoke associations with special smells. Interpersonal sympathy has to do with the proverbial “being able to smell yourself”. The sense of smell also warns humans and animals of material dangers. The highly toxic substance hydrogen sulfide (H 2 S), for example, has a very low odor threshold . Another warning substance is 2-methylisoborneol , which uses its odor to indicate its presence in putrid, inedible water and thus protects against the consumption of such water.


Although we can distinguish many smells, we usually cannot name them. This problem has been studied since ancient times . So Plato , Aristotle , Theophrast and Galen dealt with the question of how smells should be delimited and named. Smells can be divided into different scent categories from floral, ethereal and musky to sweaty and putrid. However, fragrance categorizations are always arbitrary.

One of the most frequently used classification systems for odors is the system according to John E. Amoore, which distinguishes between seven basic odors.

Basic odor typical odorous substance Occurrence
camphor-like Camphor Moth poison
musky Musk ketone Angelica
floral scented 2-phenylethanol Rose scent
menthol-like Menthone mint
ethereal 1,2-dichloroethane Dry cleaning agent
biting Formic acid Wine vinegar
foul 2-methylpropane-2-thiol rotten egg
Structural formula of ( R ) - (+) - limonene - the main odorant of lemon

But there are also other approaches to classification. Hennings odor prism (1915): The basic smells form the corners, the other smells can be represented as a mixture of neighboring basic smells and thus lie on the edges of the prism.

Basic odor typical odorous substance Occurrence from - to
flowery 2-phenylethanol Vanilla - geranium
fruity Limes Orange - lemon
resinous Bitumen - eucalyptus
spicy Clove - ginger
foul 2-methylpropane-2-thiol rotten egg

Günther Ohloff , who was one of the leading scientists in the field of aromatic substances, created another classification system for odor qualities :

Basic odors and the associated olfactory notes according to Ohloff
Basic odor: flowery fruity green spicy woody resinous animalistic earthy
associated olfactory notes
  • jasmine
  • rose
  • violet
  • mimosa
  • Orange blossom
  • lily of the valley
  • Citrus fruits
  • Apple
  • raspberry
  • strawberry
  • pineapple
  • Passion fruit
  • Beech leaves
  • Cucumbers
  • hay
  • Myrtle
  • Galbanum
  • cinnamon
  • anise
  • Vanillin
  • Cloves
  • pepper
  • Fighter
  • earth
  • Mould
  • ocean


The strength of the olfactory sensation evoked by different substances varies greatly. The higher the concentration of an odorous substance in the inhaled air, the stronger the sensation. Even an extremely small amount causes a sensation of smell. So bromine can still be smelled in a concentration of 33 milligrams of bromine in one cubic meter of air. Musk is still perceived when the nose is presented with less than 1 / 2,000,000 milligrams of a spirit musk extract ; less than a millionth of hydrogen sulfide is clearly perceived in the air. The sense of smell of many animals is much more finely developed. Butyl selenomercaptan and ethyl mercaptan are considered the most malodorous compounds in the world for humans .

With the duration of an olfactory impression, the olfactory mucous membrane gradually tires. If we stay in smelling air for a long time, the odor perception for the constant odor (so-called phasic reception ) disappears without the ability to perceive other smells decreasing. This is due to the material link. Every odor stimulus (odor substance = key) is recognized in one (or more) special odor receptors (= lock) that need a reactivation phase; the non-stimulated receptors with their nerves are still available. The designation of smells as pleasant or unpleasant, which is purely individual and arbitrary, is based in part on ideas that relate to the perception of smell. These ideas change with the physiological state of the body. The hungry , for example, smells a dining extremely pleasant to the nose, while the excited Saturated reluctance.

Social importance

Some smells are of high cultural importance, as is the case with incense as a gift of the Three Kings . The term aroma means in ancient Greek (ἄρωμα ároma ), spice 'or' fragrant herb 'and expresses such a positive evaluation. The similarity of odorous substances from spices such as cinnamon or vanilla with human “pheromones” has an euphoric effect.

Often unpleasant smells are supposed to be masked by perfumes . These include bad breath (metabolic products of bacteria as a result of poor oral hygiene or from foods such as garlic), flatulence, sweat (containing butyric acid). Perfume production is an important branch of the cosmetics industry. Intense body odors, including applied perfumes, can, however, be very annoying within groups of people (choir, school class).

Talkative olfactory metaphors are often used when expressing vague rejection:

  • "I can't smell it"

Physiological measurement

Dynamic olfactometry , which is standardized by the EN 13725: 2003 standard, has established itself as the measurement method for odors . This determines how much an odor sample has to be diluted in order to reach the odor threshold , i.e. the concentration at which the odor is only perceived by half of a panel of testers. This dilution ratio represents the numerical value of the odorant concentration; its unit is GE E / m 3 (“ European odor unit per cubic meter”). Even if the concentration of an odorous substance is below the detection limit of a chemical-physical measurement method, there is still the possibility that an odor sensation will still be caused.

The olf was proposed as a further unit of smell . The level of contamination produced by an adult person with 1.8 square meters of skin surface in a sedentary occupation with a hygiene level of 0.7 baths per day (this corresponds approximately to one shower / bath every 36 hours) is indicated with an olf.

See also


  • C. Bushdid, MO Magnasco, LB Vosshall, A. Keller: Humans Can Discriminate More than 1 Trillion Olfactory Stimuli . In: [1]
  • Thomas Hummel, Antje Welge-Luessen: Smell and taste disorders . Thieme, Stuttgart, 2008
  • Bavarian State Office for the Environment: Odors and unpleasant odors . In: Odors and odor nuisance - Bayern.de ( Memento from June 25, 2006 in the Internet Archive )
  • Julius Bernstein : The five senses. Leipzig 1875.
  • Thomas Braun: Chemical Senses . In: Thomas Braun et al .: Short textbook Physiology . Elsevier, Urban & Fischer, 2007.
  • Renate Cervinka, Ernst Neudorfer: Psychometric recording of odor nuisance . In: Hazardous substances - keeping the air clean , 65 (6), 2005 ISSN  0949-8036 pp. 271–274
  • Hippolyte Cloquet: Osphresiology or the study of smells, of the sense of smell etc. Verlag des Landes-Industrie-Comptoirs, Weimar 1824 Scan , ebook at Bayerische Staatsbibliothek , Munich 2009 (free of charge)
  • Wilhelm Hack : Smell and the organ of smell. A popular lecture given at Freiburg and Karlsruhe in the spring of 1885. JF Bergmann, Wiesbaden 1885 full text, online access to vd. File formats, e.g. B. Daisy.zip
  • Hannah Monyer: In the jungle of fragrances In: Magazine of the University of Heidelberg , Ruperto Carola , Heft 3, 2005
  • Tim C. Pearce et al. Nagle (Editor): Handbook of Machine Olfaction. Electronic Nose Technology , Wiley-VCH, Wiesbaden 2002, ISBN 3-527-30358-8 .
  • Jürgen Raab: Sociology of Smell . UVK, Konstanz 2001, ISBN 3-89669-980-6
  • Max von Vintschgau: Physiology of the sense of smell . In Ludimar Hermann Hg .: manual of the physiology of the sensory organs . Manual of Physiology, Vol. 3, 2nd CW Vogel, Leipzig 1880, pp. 143-286 online
cultural-historical representations

Web links

Wiktionary: Smell  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. C. Bushdid, MO Magnasco, LB Vosshall, A. Keller: Humans Can Discriminate More than 1 Trillion Olfactory Stimuli. Science 21, March 2014, Vol. 343, No. 6177, pp. 1370-1372. doi : 10.1126 / science.1249168
  2. ^ Georg Wöhrle: Ancient efforts for a system of smells . In: Würzburg Yearbooks for Classical Studies (NF) . No. 13 , 1987, pp. 95-100 .
  3. Harry T. Lawless: Exploration of fragrance categories and ambiguous odors using multidimensional scaling and cluster analysis. In: Chemical Senses , Vol. 14, No. 3, 1989, pp. 349-360. doi : 10.1093 / chemse / 14.3.349 .
  4. Odors and odor nuisance ( Memento from June 25, 2006 in the Internet Archive )
  5. How does smelling actually work? www.inb.uni-luebeck.de, May 25, 2014.
  6. ^ Günther Ohloff: Earthly scents, heavenly lust. A cultural history of fragrances . Birkhäuser, Basel, ISBN 3-7643-2753-7 , page 11.
  7. Guinness World Records 2009 .
  8. DIN EN 13725: 2003-07 air quality; Determination of the odor concentration with dynamic olfactometry; German version EN 13725: 2003. Beuth Verlag, Berlin. P. 4.
  9. VDI 3881 sheet 1: 1986-05 olfactometry; Odor threshold determination; Fundamentals (olfactometry; odor threshold determination; fundamentals). Beuth Verlag, Berlin. P. 3.
  10. Youth book. Quotes with reference to childhood smells from the book in the review by Martin Jürgens , Entfarben der Kindheit , specifically , 10, 2016, p. 17.