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50 free Gross trivia questions with answers — science & nature quiz, new questions added Aug 2026.
48 free gross trivia questions with answers. This gross trivia quiz is a tour of the disgusting side of biology and history, all of it true. It starts with you: what lives in your bed, what lives on your face, what earwax is made of and what actually makes a fart smell. Then it moves to the animals that out-gross us: rabbits that eat their own droppings, lizards that squirt blood from their eyes, birds that poop on their legs to cool down, beetles that fire boiling spray, and the whale by-product that ends up in perfume. There is a food section that is not for the squeamish (maggot cheese, fermented shark, civet coffee, birds fermented in a seal) and a history section on Roman toilet sponges, powdered-mummy medicine, the courtier who wiped the king and the summer London's river stank so badly Parliament fled. About forty percent of the questions are easy enough for a family car ride, and none of them is graphic beyond 'eww'. Every answer has been checked against a primary source and shows its citation once you have answered.
30 of 50 questions with answers and explanations. Play the quiz
Q 01What do house dust mites mostly eat?
Flakes of human skin
A single mite produces about 2,000 droppings in its ten-week life, and those droppings are the allergen, not the mite.
Q 02Detectable dust-mite allergen was found in the beds of roughly what share of surveyed US homes?
84%
Europe fared a little better at 68 percent; the mites simply prefer humid places.
Q 03Demodex mites live in the hair follicles of your face. Roughly what share of elderly people carry them?
Two-thirds
A small 2014 study found them on every adult tested; they eat skin cells and oil, and mate at the mouth of the follicle.
Q 04What is earwax mostly made of?
Shed skin cells
On average about 60 percent of it is keratin, the same protein as your hair and nails.
Q 05There are two genetically determined types of human earwax. What are they?
Wet and dry
A single letter change in one gene decides it; the dry, flaky type is common in East Asia and among Native Americans.
Q 06Over 99% of a fart is odourless gas. What produces most of the smell in the remaining trace?
Sulfur compounds
Hydrogen sulfide tracks most closely with how bad people rate the smell, followed by methyl mercaptan.
Q 07The scientific study of intestinal gas has what name?
Flatology
Flatus, the medical word, covers gas from the stomach or bowels; a fair share of it is simply swallowed air.
Q 08Does everyone's flatulence contain the same greenhouse gas that cows belch?
No, only people with certain gut archaea
In one study, only five of nine adults carried the microbes needed to make it.
Q 09What compound is the main source of the smell of faeces, yet is used in low doses in perfumes?
Skatole
Its name comes from the Greek skato-, meaning dung; diluted enough, it smells of flowers.
Q 10Roughly what percentage of urine is water?
91 to 96%
The rest is mostly urea, plus salts and whatever pigments you ate; asparagus can turn it green.
Q 11Because it was essential for cleaning wool, which body fluid was taxed in ancient Rome?
Urine
Stale urine, called lant, supplied the ammonium salts that whitened cloth in the fulling trade.
Q 12The 'sponge on a stick' found in Roman public latrines has traditionally been assumed to be what?
A shared bottom-wiping tool
Recent scholarship suggests it may have been a toilet brush after all; either way, the sponge was rinsed in vinegar and shared.
Q 13Which English court official helped the king on the toilet and became hugely powerful as a result?
Groom of the Stool
Q 21Some cockroaches can survive on which unlikely food source?
The glue on postage stamps
The American cockroach also eats leather, book bindings, hair, dead insects and dirty laundry.
Q 22What do rabbits and guinea pigs do with the soft, sticky pellets called cecotropes that they produce?
Eat them
The pellets come from the caecum packed with vitamins and protein; a second pass through is the only way to absorb them.
Q 23Hagfish slime swells to what multiple of its volume in under half a second?
10,000 times
It clogs a predator's gills; the hagfish then ties itself in a travelling knot to scrape the goo off its own body.
Under Henry VIII the job came with a bowl, water, towels and a duty to monitor the royal bowels; it was abolished only in 1901.
Q 14From the 12th century on, what was the apothecary medicine 'mummia' made from?
Ground-up Egyptian mummies
It began as a word for bitumen; when supplies ran short, dealers substituted whole embalmed bodies, and painters used the powder as 'mummy brown'.
Q 15The "Great Stink" of 1858, when the smell of sewage forced Parliament to act, happened in which city?
London
Joseph Bazalgette's resulting sewer system still serves nine million Londoners today.
Q 16Which famous scientist tested the filth of the Thames in 1855 by dropping pieces of white paper into it?
Michael Faraday
He wrote to The Times that near the bridges the muck 'rolled up in clouds so dense that they were visible at the surface'.
Q 17The earliest recorded reference to toilet paper, from around 589 AD, comes from which country?
China
The scholar Yan Zhitui wrote that he dared not use paper bearing the names of sages 'for toilet purposes'.
Q 18How long can a bed bug survive without feeding?
About 300 days
That is why infestations are so hard to clear; Egyptian fossils show they have been biting people for 3,500 years.
Q 19Head lice and body lice are thought to have split into subspecies at what point in human history?
When humans began wearing clothes
The genetic split, 30,000 to 110,000 years ago, is one of the odder clues to when we got dressed.
Q 20Cockroaches do not have lungs. What happens if one loses its head?
It can keep breathing
They breathe through spiracles along the body; some species can also go 45 minutes without air and a month without food.
Q 24Storks and vultures cool down by doing what onto their own legs?
Defecating
The habit is called urohidrosis; bird droppings are urine and faeces combined, so the liquid evaporates and chills the skin.
Q 25Turkey vultures find carcasses by smelling which gas given off by early decay?
Ethyl mercaptan
Their olfactory lobe is unusually large; the same compound is added to natural gas so humans can smell leaks.
Q 26Owls cough up fur and bones as pellets. How soon after a meal does a pellet form?
Six to ten hours
School dissections of unsterilised pellets have caused salmonella outbreaks, because rodent viruses survive the trip.
Q 27Several species of horned lizard defend themselves by squirting what from the corners of their eyes?
Blood
They can aim it about five feet, and it tastes terrible to dogs and coyotes, possibly thanks to a diet of venomous ants.
Q 28Fulmar chicks defend the nest by spraying attackers with what?
Foul-smelling stomach oil
The name comes from Old Norse for 'foul gull'; the oil mats a predator's feathers so it cannot fly.
Q 29The hoatzin of the Amazon is nicknamed the 'stinkbird' because it does what?
Ferments leaves in its gut like a cow
The bacterial fermentation gives it a manure-like smell, so locals hunt it only in dire need.
Q 30Wombats are the only animal known to produce droppings of what shape?
Cubes
The physicists who worked out how won an Ig Nobel Prize.