50 Fun Facts About Sense of Smell

What did Apollo astronauts say Moon dust smelled like when their spacesuits carried it into the cabin?

Gunpowder is how the moonwalkers described the dust that rode back inside on their suits. Harrison Schmitt of Apollo 17 called his reaction to it lunar hay fever.

What name did two Australian scientists coin for the earthy scent of rain falling on dry ground?

Petrichor comes from oils that build up in rock and soil during dry spells and are set free by moisture. Isabel Bear and Dick Thomas named it in the journal Nature in 1964.

Which household fuel has had a rotten-egg odour added ever since a 1937 Texas school explosion?

Natural gas has no smell of its own, so the leak that filled the Texas school went unnoticed. Within weeks of the blast, a sulphur compound was being added as a warning.

Which spiky Southeast Asian fruit is banned from Singapore's public transport because of its lingering smell?

Durian is known across the region as the king of fruits. Its odour can hang about for days, so some hotels turn it away as well.

Which mammal carries nearly 2,000 working smell-receptor genes, about five times as many as humans have?

The African elephant has more than twice as many of these genes as a dog. Researchers in Tokyo found the total when they compared thirteen mammal species.

Which waxy substance from the gut of sperm whales was long prized for making perfume last longer?

Ambergris is thought to form around the sharp beaks of squid that the whale has swallowed. Perfume makers now mostly use a synthetic substitute.

Which green spring vegetable contains a sulphur compound that gives urine a strong smell soon after eating?

Asparagus owes the effect to asparagusic acid, a sulphur compound found in no other vegetable. A French treatise on food was already remarking on the smell in 1702.

Which children's modelling compound had its signature scent registered as a trademark by Hasbro in 2018?

Play-Doh began life in 1930s Cincinnati as a putty for wiping coal soot off wallpaper. It was relaunched as a toy once demand for the cleaner had shrunk.

Which Sumatran plant heats its towering flower spike to spread a stench of rotting flesh?

The titan arum warms its spike to about human body temperature, which helps the smell reach the carrion insects that pollinate it. Each bloom lasts only a day or so.

Which large hunting dog breed has been used to track people by scent since the Middle Ages?

The bloodhound was first bred to hunt deer and wild boar. Medieval Scottish stories tell of sleuth hounds being put on the trail of Robert the Bruce.

What is the medical term for a total loss of smell, a widely reported symptom of COVID-19?

Anosmia is risky as well as dulling, because it hides gas leaks, smoke and spoiled food. People who have it can still taste, but the flavours of a meal go missing.

Which German city gave its name to a citrus fragrance first mixed there by Giovanni Maria Farina?

Cologne became the perfume's name because Farina, an Italian, wanted to honour his new hometown. He wrote to his brother that the scent recalled an Italian spring morning after rain.

Which prized underground fungi were pigs traditionally used to sniff out beneath oak and hazel trees?

Truffles are now mostly hunted with trained dogs, because a pig tends to eat what it finds. Tests in 1990 found that both animals home in on dimethyl sulfide in the fungi's scent.

Which famous perfume did Ernest Beaux create in 1921 using aldehydes to boost its floral scent?

Chanel No. 5 kept the number of the sample that Coco Chanel picked from the glass vials Beaux set before her. She said the number five would bring good luck.

Which flightless New Zealand bird is the only bird with nostrils at the very tip of its beak?

The kiwi probes the ground with its long beak for worms and insects it cannot see. A keen sense of smell is unusual among birds.

Which aromatic resin from Boswellia trees was one of the gifts the Magi brought to the infant Jesus?

Frankincense is tapped from the trees two or three times a year, and the last taps give the most fragrant drops. Most of the world's supply now comes from the Horn of Africa.

Which sour citrus fruit, a staple of perfumery, gives Earl Grey tea its distinctive aroma?

Bergamot oil comes from the fruit's skin, and most of Italy's crop grows on one short stretch of the Calabrian coast. The fruit is thought to be a cross of lemon and bitter orange.

Which fish is thought to use smell to find the very stream where it hatched years earlier?

Salmon are thought to cross the open ocean by sensing the Earth's magnetic field, then follow the scent of their home river for the final stretch.

Which herb of the mint family gives off nepetalactone, a compound that repels mosquitoes, cockroaches and termites?

Catnip leaves about a third of cats completely unmoved. Leopards, cougars and lynxes have reacted to it much as pets do, while lions and tigers respond less reliably.

Which medical word for bad breath became widely known through 1920s advertisements for Listerine mouthwash?

Halitosis was coined by the physician Joseph William Howe in a book of 1874, decades before the mouthwash adverts turned it into a household worry.

What are chemical signals called, such as the airborne lure a female silkworm moth releases to attract mates?

Pheromones got their name in 1959, just after the German biochemist Adolf Butenandt identified the silkworm moth's lure, bombykol, as the first known example.

Which animal's spray is best removed with hydrogen peroxide and baking soda rather than tomato juice?

Skunk spray gets its stench from sulphur compounds, which the peroxide mix turns into odourless acids. The chemist Paul Krebaum devised the recipe in 1993.

Which toxic gas smells of rotten eggs at first but quickly deadens the sense of smell?

Hydrogen sulfide is so dangerous because the nose stops registering it, leaving victims unaware until it is too late. In tiny amounts it also helps give flatulence its smell.

Which poisonous gas from car exhausts, nicknamed the silent killer, has no smell, colour or taste?

Carbon monoxide earned the nickname among miners, who also called it whitedamp. It forms whenever a fuel such as wood, coal or petrol burns without enough air.

Which pungent gas do smelling salts release to jolt a person who has fainted back to alertness?

Ammonia inhalants are now banned in most boxing competitions, for fear the jolt could mask a serious injury. Some Victorian constables carried them to revive fainting women.

Which city endured the Great Stink of 1858, when a reeking river nearly drove its parliament out?

London answered with Joseph Bazalgette's sewers, which carried the waste away from the Thames. Parliament's riverside curtains had been soaked in lime chloride to mask the smell.

Which mosquito-borne disease takes its name from the Italian for bad air, once blamed for causing it?

Malaria kept the name even after Ronald Ross proved in 1897 that mosquitoes, not foul marsh vapours, carry the parasite. It had also been known as marsh fever.

Who in 17th-century Europe wore long beaked masks stuffed with herbs and dried flowers?

Plague doctors hoped the scents would shield them from disease carried on the air. Despite its popular image, the beaked costume is not known from the medieval Black Death.

Which kitchen bulb lingers on the breath because a sulphur compound from it is exhaled through the lungs?

Garlic breath comes from allyl methyl sulfide, which passes from the blood to the lungs and out through the skin as well. Sipping milk with the meal has been shown to reduce it.

Which pungent cheese is ripened by a bacterium that also lives on human skin and causes foot odour?

Limburger smells so much like feet that mosquitoes are drawn to both equally, a finding that won an Ig Nobel Prize in 2006.

Which brain structure relays signals from sight, hearing, taste and touch, but is bypassed by smell?

The thalamus is skipped because smell signals run straight to the forebrain, which makes smell the only human sense wired that way.

Which compound made by soil microbes gives beetroot its earthy taste and scents freshly dug ground?

Geosmin is also why some tap water, and farmed fish such as carp and catfish, can taste muddy. The human nose picks it up at well under one part per billion.

Which American biologist shared the 2004 Nobel Prize with Richard Axel for discovering the nose's odour receptors?

Linda Buck and Axel showed in a landmark 1991 paper that hundreds of genes code for the odour sensors on the nerve cells of the nose.

Which wall of bone and cartilage divides the inside of the nose into left and right airways?

The septum is built from several bones and a plate of cartilage. One that sits well off-centre is known as a deviated septum.

What name is given to the lip-curling grimace many mammals make to draw scents towards the roof of the mouth?

The flehmen response was named in 1930 by Karl Max Schneider, director of Leipzig zoo and an authority on big cats. It pulls scents to a second smell organ above the palate.

Which American scavenging bird finds hidden carcasses by smell, a rare skill among birds?

The turkey vulture flies low to catch ethyl mercaptan, a gas given off as a carcass begins to decay. Its own defence is pungent too: it throws up half-digested meat at intruders.

What is the medical name for an olfactory hallucination, the smelling of an odour that is not really there?

Phantosmia usually conjures something unpleasant, such as burning or rot. An occasional phantom smell is normal and tends to pass on its own.

Which nut is the smell of the poison hydrogen cyanide said to resemble, though many people cannot detect it?

Almonds of the bitter kind are themselves a natural source of the poison. The ability to smell it is inherited, and a large share of people lack it.

Which insects release banana-scented isoamyl acetate when they sting, rallying nestmates to join the attack?

Honey bees give off the scent from the sting apparatus as a beacon that draws others to strike. The same compound occurs naturally in fruit and in fermenting beer and whisky.

Which French novelist gives his name to the way a smell can suddenly bring back vivid memories?

Marcel Proust described in Swann's Way how a madeleine dipped in linden tea brought his past flooding back. Psychologists call recall set off by an odour the Proust phenomenon.

Which director handed out scratch-and-sniff Odorama cards with his 1981 comedy Polyester?

John Waters gave each viewer a card with ten numbered spots to scratch on cue. The stunt was his tribute to the cinema gimmicks of the showman William Castle.

Which German author wrote Perfume, a novel about a murderer in 18th-century France with a superhuman nose?

Patrick Süskind's 1985 novel spent nine years on Der Spiegel's bestseller list and has sold more than 20 million copies. Its orphan hero's surname, Grenouille, is French for frog.

Which leaf-eating Amazon bird is nicknamed the stinkbird for the manure-like odour its digestion produces?

The hoatzin ferments leaves in the front of its gut, much as cattle do, and the process smells. Its chicks have claws on their wings for scrambling around branches.

Which Southeast Asian mammal, also called the bearcat, is known for smelling like hot buttered popcorn?

The binturong owes the smell to a compound in its urine, the very one created when popcorn pops. The animal lives in trees and has a bushy tail that can grip branches.

Which family of compounds, made from an acid and an alcohol, gives many fruits their sweet smells?

Esters are behind the aroma of apples, pears, pineapples and strawberries. That is why they are so widely used in artificial flavourings and fragrances that mimic fruit.

Which town in the south of France, home to a famous jasmine harvest, is called the world's perfume capital?

Grasse was a leather-tanning town before its glove makers turned to scent. In 1614 the king recognised their new guild of glover-perfumers.

Which country's fermented herring, surströmming, smells so strong that it is usually eaten outdoors?

Sweden has eaten the dish since at least the 16th century. Just enough salt goes in to stop the fish rotting while it ferments for six months or more.

Which gas, often smelled after a lightning strike, takes its name from a Greek word meaning to smell?

Ozone was named by the chemist Christian Friedrich Schönbein, who isolated it in 1839. He recognised its sharp odour as the one that often follows a bolt of lightning.

Which African rodents does the charity APOPO train to sniff out buried landmines and tuberculosis?

Giant pouched rats are too light to set off a pressure mine as they walk across it. APOPO picked the species for its long life and its African origin.

Which small hound breed forms a brigade that sniffs luggage at US airports for forbidden food and plants?

The Beagle Brigade began at Los Angeles International Airport in 1984. Its dogs are donated by owners and breeders or rescued from animal shelters.