48 Fun Facts About Gross

What do house dust mites mostly eat?

Flakes of human skin work their way deep into mattresses, pillows and sofas, so that is where the mites gather; most people meet them while asleep in bed.

House dust mites never bite, so what sets off most dust-mite allergies?

Proteins in their droppings, mostly leftover digestive enzymes, cause the reaction once breathed in; one national survey found the allergen in the beds of about four in five American homes.

Demodex mites are eight-legged relatives of spiders that spend their lives where on the human body?

In facial hair follicles, tucked out of sight: researchers could see the mites on only 14% of volunteers, yet DNA tests found them on every adult they checked.

What is earwax mostly made of?

Shed skin cells, rich in the protein keratin, make up most of it; the ear canal's skin creeps outward like a conveyor belt, and chewing or talking helps work the wax out.

Human earwax comes in which two genetically determined types?

Wet and dry earwax are set by a single letter of DNA in one gene; the dry version, common in East Asia, also leaves people with far less armpit odour.

Over 99% of a fart is odourless gas, so what produces most of the smell in the remaining trace?

Sulfur compounds, led by rotten-egg hydrogen sulfide, matched the scores when two judges sniffed samples for a 1998 study; a charcoal-lined cushion then soaked up over 90% of those gases.

Which medical term names the rumbling of gas moving through your intestines?

Borborygmus comes from a Greek word coined to imitate the noise itself. The rumble is gas being squeezed along the gut, and it is loudest when there is no food inside to muffle it.

What compound is the main source of the smell of faeces, yet is used in low doses in perfumes?

Skatole takes its name from the Greek for dung, yet at low concentrations it smells floral: it occurs naturally in jasmine and orange blossom, which is why perfumers use it.

Which waste compound does the liver make from the toxic ammonia left over when the body breaks down protein?

Urea is the body's safe way to dump spare nitrogen: ammonia would poison the brain if it built up, so the liver converts it and the kidneys flush the result away.

Because it was essential for cleaning wool, which body fluid was taxed in ancient Rome?

Urine left to go stale gave launderers the ammonia that cleaned wool. When his son Titus complained about the tax, Emperor Vespasian held a coin to his nose and asked if it smelled.

The 'sponge on a stick' found in Roman public latrines has traditionally been assumed to be what?

A shared bottom-wiping tool is the classic reading: Seneca mentions the sponge stick, and latrines kept salt water or vinegar to rinse it. Some scholars now argue it only scrubbed the toilet.

Which English court official helped the king on the toilet and became hugely powerful as a result?

The Groom of the Stool brought the bowl, water and towels, and the privacy paid off: he became the king's private secretary, kept his personal accounts and decided who got in to see him.

Which grisly apothecary medicine did European painters also buy as a brown pigment?

Ground-up Egyptian mummies were thought to hold healing bitumen. To keep the trade supplied, dealers later passed off the dried bodies of executed criminals as the real thing.

The "Great Stink" of 1858, when the smell of sewage forced Parliament to act, happened in which city?

Joseph Bazalgette's resulting sewer system still serves nine million Londoners today.

Which famous scientist tested the filth of the Thames in 1855 by dropping pieces of white paper into it?

Michael Faraday wetted the scraps so they would sink and dropped some in at every pier; they vanished from sight before sinking an inch. Punch then drew him handing his card to Father Thames.

The earliest recorded reference to toilet paper, from around 589 AD, comes from which country?

China had paper to spare centuries before Europe: the scholar Yan Zhitui wrote that he dared not use sheets bearing the names of sages for toilet purposes, and by the 14th century it was being mass-produced.

Bed bugs home in on a sleeping person mainly by body warmth and what else?

Carbon dioxide in breath draws bed bugs to a sleeper, along with body warmth. Dirt plays no part, so a spotless bedroom suits them as well as a filthy one.

Head and body lice are thought to have split at which point in human history?

When humans began wearing clothes, some lice moved off the scalp and into the fabric, where body lice live and lay their eggs. Their DNA is now one of the few clues to when people first got dressed.

Cockroaches have no lungs, so what happens if one loses its head?

It can keep breathing because air enters through small holes in each body segment and the brain plays no part. It does not bleed out either, so a headless cockroach can live on for days.

Some cockroaches can survive on which unlikely food source?

The glue on postage stamps is a meal to a cockroach, as are soap, toothpaste, hair and book bindings. Being cold-blooded, they can also go about a month with no food at all.

What do rabbits and guinea pigs do with the soft, sticky pellets called cecotropes that they produce?

Rabbits and guinea pigs eat them as soon as they appear: microbes in the caecum make B vitamins and protein too far down the gut to be absorbed, so a second trip through is the only way to collect them.

Hagfish slime swells to what multiple of its volume in under half a second?

10,000 times is the measured figure, as coiled threads unspool and trap seawater. The slime clogs a predator's gills, and the hagfish ties itself in a sliding knot to scrape the goo off its own body.

Storks and vultures cool down by doing what onto their own legs?

Defecating on their bare legs stands in for sweating, which birds cannot do: the liquid evaporates and carries heat away.

Turkey vultures find carcasses by smelling which gas given off by early decay?

Ethyl mercaptan is the same stink added to odourless fuel gas so people can smell a leak, and oil company engineers noticed turkey vultures gathering wherever a pipeline was leaking it.

In which muscular organ does an owl press leftover fur and bones into the pellet it coughs up?

The gizzard holds back the fur and bones that stomach acid can't dissolve and squeezes them into a lump of its own shape. Unlike hawks, owls have no crop, so prey drops straight into the stomach.

Which reptile defends itself by squirting blood from the corners of its eyes?

The horned lizard eats stinging harvester ants, and a compound from their venom is thought to end up in its blood, which would explain why the squirt tastes foul to dogs, coyotes and wild cats.

Fulmar chicks defend the nest by spraying attackers with what?

Foul-smelling stomach oil gave the fulmar its name, from Old Norse words for foul and gull. On a predatory bird it sets and mats the wing feathers, which can leave the attacker unable to fly.

The Amazon's hoatzin is nicknamed the 'stinkbird' because it does what?

It ferments leaves in its gut like a cow, the only bird that does, brewing them with bacteria in an oversized crop. The result reeks of fresh manure, and the bulky crop makes it a clumsy flier.

Wombats are the only animal known to produce droppings of what shape?

Cubes take shape in the last stretch of the wombat's gut, where stiff and soft bands of the wall squeeze at different speeds. The physicists who worked it out won an Ig Nobel Prize in 2019.

Ambergris, a prized perfume fixative, forms in the digestive system of which animal?

The sperm whale eats squid, and scientists think it coats their sharp beaks in a fatty gut secretion. Fresh, the lump smells faecal; years of sun and salt water turn it sweet and earthy.

Which two chemicals react to make the bombardier beetle's boiling spray?

Hydroquinone and hydrogen peroxide sit together harmlessly until the beetle squeezes them into a chamber of enzymes. The blast nears the boiling point of water and fires in rapid pulses, like a V-1 flying bomb.

The female Surinam toad carries her eggs where until fully formed froglets emerge months later?

Embedded in the skin of her back, each egg gets its own pocket with a lid. The male rolls them on as the pair somersault underwater, and her skin grows up around them within hours.

Which biting pest does the female human botfly catch and load with her eggs to reach a person?

A mosquito does the delivery: the botfly catches one, attaches her eggs to its belly and lets it go. When it lands on a person to feed, the eggs hatch and the larvae burrow into the skin.

Honey is made by bees repeatedly doing what to nectar?

Regurgitating it from bee to bee dries the nectar until it is only about 18 per cent water. At that point mould and bacteria can't grow in it, which is why honey doesn't spoil.

The red food colouring carmine (E120), used in yogurt, sweets and lipstick, is made from what?

Crushed insects, to be exact: female cochineals from the prickly pear cacti of Mexico, dried and ground. The Aztecs dyed with them, and once Spain shipped the dye home in the 1520s it displaced kermes, Europe's older insect red.

The 'confectioner's glaze' that makes sweets shiny is a resin secreted by which insect?

The lac bug crusts tree twigs in southern Asia with the resin, better known as shellac. Melted into flakes, the same stuff was pressed into 78 rpm gramophone records until vinyl took over.

Kopi luwak coffee is made from beans that have passed through which animal?

The Asian palm civet is said to pick only the ripest coffee cherries. The price brought a grimmer method: reporters have found civets kept in battery cages and force-fed the fruit.

Casu martzu, a Sardinian sheep's-milk cheese banned from sale, contains what?

Live fly maggots do the ripening: cheese flies lay eggs in cracks in the pecorino, and the grubs digest it into a soft, creamy paste. Sardinians eat it grubs and all.

Iceland's pungent delicacy hákarl is the fermented meat of which animal, toxic if eaten fresh?

Shark, specifically the Greenland shark, whose fresh flesh is toxic. Weeks of fermenting break the toxins down, and by the time the meat has hung to dry it reeks of ammonia.

Surströmming, said to be one of the most putrid-smelling foods on earth, is fermented what?

Baltic herring keeps fermenting inside the sealed tin until it bulges. In 2006 airlines including British Airways and Air France banned the cans as potentially explosive, to the fury of Swedish producers.

Kiviak, a Greenlandic winter dish, is made by fermenting up to 500 whole small birds inside what?

A seal skin is stuffed with little auks, beaks and feathers included, then sewn shut, sealed with fat and left under a heavy rock for months. It is eaten during the Arctic winter, often at celebrations.

What kind of substance cures a century egg?

An alkaline mix of clay, ash and lime does the job heat normally does: over weeks it sets the raw white into a dark, translucent jelly.

The durian's smell has got it banned from public transport and many hotels in which two cities?

Singapore and Bangkok both bar the fruit from public transport. In 2018 an Indonesian airliner sat on the tarmac until sacks of durian were hauled out of the hold, after passengers revolted at the smell.

The word 'skunk' comes from an Algonquian word combining 'fox' with what?

To urinate plus fox: the Algonquian name amounts to 'urinating fox'. English borrowed it in the 1630s and later made it a verb, so to skunk an opponent is to beat them without letting them score.

Plutarch wrote that Egypt's sacred scarabs, all male, reproduced how?

By depositing semen into a ball of dung, the story went, since no female beetles were thought to exist. The ball rolling along looked like the sun crossing the sky, so the scarab became Khepri, god of the rising sun.

Bacteria were once said to outnumber your own cells ten to one; what is the newer estimate?

About as many: roughly 38 trillion bacteria to 30 trillion human cells. Most of the bacteria sit in the colon, so the researchers noted that one trip to the toilet may tip the balance back to human.

Through which body opening do sea cucumbers 'breathe', drawing water into their respiratory trees?

The anus pumps water in and out, and that current gives the sea cucumber away. Slender pearlfish follow it, back in tail first and spend the day hiding inside, slipping out at night to feed.

Naked mole-rat workers turn into devoted babysitters after eating hormone-rich droppings from whom?

The colony's queen is its only breeding female, and while she is pregnant her droppings carry the hormone estradiol. Workers that feed on them grow more responsive to crying pups, just in time for the litter.