Human Skin Trivia
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100 free Human Skin trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Skin is the organ you look at all day and rarely think about, and this quiz is built to change that. It starts with the numbers: what share of your body it makes up, how much area it covers, how many sweat glands and nerve endings fit in a square inch, and how many species of bacteria call it home. Then it goes layer by layer through the epidermis and dermis, the extra stratum that makes palms 'thick skin', the cells that make up 95 percent of the surface, and how the whole outer layer replaces itself in about seven weeks. The middle of the quiz is about colour and reaction: what melanin's name means, which type of pigment turns hair red, why dark and light skin have the same number of melanocytes, the gene behind freckles, the reflex behind goose bumps and Darwin's verdict on blushing. Fingerprints get a full run, from the fetal week they form to Faulds, Galton, Scotland Yard and the people born without any. Then tattoos, Ötzi's 61 of them, sunburn, the chemist who invented SPF, the sticky wartime origin of Coppertone, scars, acne, dandruff and calluses. The easy tier is fair for a school biology class; the expert questions reach tyrosine, adermatoglyphia and the Hôpital Saint-Louis. Every answer was checked against Wikipedia's articles on skin, its structures and its conditions, and the supporting sentence is attached to each question.
30 of 100 questions with answers and explanations. Play the quiz
Q 01Skin is the body's heaviest organ, so which is the heaviest organ inside the body?
The liver
The liver, at about 1.5 kg, leads the internal organs, but the skin easily outweighs it: at 3.5 to 10 kg it makes up around a seventh of an adult's body weight.
Q 02Spread out flat, an average adult's skin would roughly cover what?
A single bed
A single bed: adult skin covers 1.5 to 2 square metres, about one mattress top, and doctors work out each patient's figure from height and weight to set chemotherapy doses.
Q 03What are the three primary layers of human skin, from outside in?
Epidermis, dermis, hypodermis
Epidermis, dermis, hypodermis: a thin barrier that is shed constantly, a tough middle layer that carries the nerves and sweat glands, and a bed of fat that cushions muscle and bone.
Q 04The prefix 'epi' in epidermis comes from Greek and means what?
Over or upon
Over or upon: Greek epi, 'upon', plus derma, 'skin', makes the epidermis the layer on top, just as an epicentre is the point on the surface directly above an earthquake's focus.
Q 05With no blood supply of its own, where does the epidermis get almost all of its oxygen?
The surrounding air
The surrounding air: oxygen diffuses straight in and supplies the epidermis almost entirely, so the blood beneath adds little, although the cells' food still has to seep up from capillaries below.
Q 06Fingertips wrinkle in the bath because nerves make what constrict beneath the skin?
Blood vessels
Blood vessels: a nerve signal narrows them, the fingertip's pulp shrinks and the skin above puckers, which is why fingers with nerve damage stay smooth however long they soak.
Q 07Which outermost layer of the epidermis is a sheet of dead, flattened cells?
Stratum corneum
Stratum corneum, literally the 'horny layer': its dead, scale-like cells flake away constantly and are replaced from below, so the surface you touch is never living tissue.
Q 08Which cell type makes up roughly nine in every ten cells of the epidermis?
Keratinocytes
Keratinocytes: as they are pushed up towards the surface they fill with keratin, the tough protein of hair and nails, then die and harden into the skin's outer shield.
Q 09Roughly how long does the skin take to replace its whole outer layer with new cells?
A month or two
A month or two: estimates run from four to about seven weeks for a new cell to rise to the surface, die and flake off, so the skin you see today was not there last season.
Q 10Where on the human body is the skin at its thinnest?
Around the eyelids
Around the eyelids: the skin there has no layer of fat beneath it, which helps make it the thinnest on the body.
Q 11Which skin condition, confirmed by Michael Jackson's autopsy, leaves white patches where the skin has lost its pigment?
Vitiligo
Vitiligo: Jackson told interviewers that the disease, and not bleaching, had lightened his skin, and the doctor who performed his autopsy confirmed the diagnosis to a Los Angeles jury in 2013.
Q 12The English word 'skin' is borrowed from Old Norse 'skinn', which originally meant what?
Animal hide
Animal hide: the Anglo-Saxons' own word for skin was 'hide', so the two have since traded places, with the Norse loan covering people and the native word left to cattle.
Q 13Which part of a fingernail takes its name from the Latin for 'little skin'?
The cuticle
Q 21Light and dark skin hold similar numbers of pigment cells, so what mainly sets their colour apart?
Packaging of eumelanin in melanosomes
Packaging of eumelanin in melanosomes: dark skin carries its pigment in many larger granules spread singly through each cell, while light skin bundles small ones in clusters of two or three.
Q 22Freckles form not because there are more melanocytes but because existing ones do what?
Overproduce melanin granules
UV-B exposure ramps up production, which is why freckles darken in summer.
Q 23Freckling is linked to variants of which gene, also associated with red hair?
MC1R
The cuticle: Latin cuticula is the diminutive of cutis, 'skin', the same word that gives doctors 'cutaneous' for anything to do with the skin.
Q 14Which of these animals, like humans, cools itself mainly by sweating all over its body?
The horse
The horse: cooling by sweat is rare among mammals, but horses pour it out, and a soap-like protein in it whips up the white lather you see on a hard-ridden horse.
Q 15Which group of bacteria, among the commonest on healthy skin, includes the drug-resistant superbug MRSA?
Staphylococcus
Staphylococcus: MRSA is short for methicillin-resistant Staphylococcus aureus, and like its cousins it usually lives harmlessly on the skin, causing infection only if it gets inside the body.
Q 16Which animal's skin is so like ours in thickness and hair follicles that wound dressings are tested on it?
Pig
Pig: its skin matches ours far better than a rat's or rabbit's, so studies of healing, drug patches and sunburn that cannot be run on people are often run on pigs.
Q 17The pigment melanin takes its name from a Greek word meaning what?
Black or dark
Black or dark: Greek melas also lies behind melancholy, literally 'black bile', the fluid that ancient doctors blamed for a gloomy temper.
Q 18Which form of melanin is largely responsible for the red or yellow tint of some skin and hair?
Pheomelanin
Pheomelanin: it gives almost no protection from ultraviolet light, so redheads, whose pigment cells make mostly this form, tend to burn and freckle where others tan.
Q 19The skin builds its pigment melanin from which amino acid, named after the Greek word for cheese?
Tyrosine
Tyrosine, which Justus von Liebig first got out of cheese in the 1840s: the enzyme that starts turning it into melanin is tyrosinase, and faults in its gene cause one form of albinism.
Q 20Melanocytes, the pigment-making cells, sit in which layer of the skin, right where epidermis meets dermis?
The stratum basale
The stratum basale, the bottom row of the epidermis: each melanocyte begins in the embryo's neural crest, travels to the skin and then hands its pigment to the ordinary skin cells around it.
MC1R: the gene builds a switch on pigment cells that tells them to make dark, protective melanin, and the variants common in redheads weaken it, so the cells turn out a pale red-yellow pigment instead.
Q 24Strong evolutionary pressure for dark skin acted on early Homo about how long ago?
1.2 million years ago
1.2 million years ago: our ancestors had shed their fur to cool by sweating, and dark pigment is thought to have spread to shield the folate in their blood, which strong ultraviolet light breaks down.
Q 25The Fitzpatrick scale, developed in 1975, classifies human skin by what?
Its response to UV light
Its response to UV light: Thomas Fitzpatrick drew it up to set safe starting doses of ultraviolet therapy for psoriasis, and it runs from Type I, which always burns, to Type VI, which never does.
Q 26Which nutrient does the skin synthesise for itself when exposed to ultraviolet B in sunlight?
Vitamin D
Vitamin D: too little softens growing bones into rickets, and because weak winter sunlight cannot make enough, Britain's NHS advises everyone to consider a supplement through autumn and winter.
Q 27What is the medical name for the reflex that produces goose bumps?
Piloerection
Piloerection: a tiny muscle at the root of each hair tightens and pulls it upright, which helps a furry animal keep warm or look bigger but on our sparse body hair leaves only bumps.
Q 28Which division of the nervous system fires goose bumps when you are cold or frightened?
Sympathetic
Sympathetic: the same nerves that speed the heart in a fright also stand each hair on end, and a threatened porcupine raises its quills by exactly this reflex.
Q 29Which naturalist called blushing 'the most peculiar and the most human of all expressions'?
Charles Darwin
Charles Darwin gave blushing a chapter of The Expression of the Emotions in Man and Animals in 1872, arguing that monkeys redden with passion but that no animal could be shown to blush.
Q 30At what stage of life do the ridges of a person's fingerprints take shape?
Before birth
Before birth: the ridges begin to form around the third month of pregnancy and are complete by the sixth, and the pattern they settle into then stays the same for the rest of a person's life.