Munchrd?
Munchrd: Can you be allergic to the cold?The Body

Can you be allergic to the cold?

Yes. The condition is called cold urticaria, and cold exposure makes the skin erupt in itchy welts and hives. It works when…

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Munchrd: Can you be allergic to the sun?The Body

Can you be allergic to the sun?

Yes, you really can. A group of conditions called photosensitivity disorders make the immune system react to UV-exposed skin,…

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Munchrd: Why are you taller in the morning?The Body

Why are you taller in the morning?

You genuinely are taller in the morning, usually by about 1 to 2 cm. The soft discs between your vertebrae are mostly water,…

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Munchrd: Why do wisdom teeth come in so late?The Body

Why do wisdom teeth come in so late?

Wisdom teeth arrive last because they are built last: the buds only start forming around age 7 to 9, and a tooth cannot erupt…

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Munchrd: Why do you get muscle cramps?The Body

Why do you get muscle cramps?

A cramp is a sudden, involuntary, sustained muscle contraction that won't release. The old story blamed dehydration and…

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Munchrd: Why do you get shorter as you age?The Body

Why do you get shorter as you age?

You get shorter mostly because the soft discs between your spinal bones dry out and flatten with age, shortening your trunk.…

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Munchrd: Why do your eyes water when you yawn?The Body

Why do your eyes water when you yawn?

When you yawn, you usually scrunch your eyes shut hard. That muscle squeeze presses on your tear glands, pushing out fluid…

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Munchrd: Why does your body stop growing?The Body

Why does your body stop growing?

Your height comes from thin bands of cartilage near the ends of your bones called growth plates. During puberty, sex hormones…

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Munchrd: Why does your eye twitch?The Body

Why does your eye twitch?

The common eye twitch is called eyelid myokymia: a fine, rippling misfire of the muscle that rings your eye. A few…

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Munchrd: Why does your mouth water?The Body

Why does your mouth water?

Your mouth waters because three pairs of salivary glands are always working, and a nerve reflex can ramp them up instantly.…

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Munchrd: Why does your voice break?The Body

Why does your voice break?

Your voice breaks because puberty rebuilds the instrument that makes it. A surge of testosterone makes the voice box grow and…

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Munchrd: Why don't scars grow hair?The Body

Why don't scars grow hair?

Hair grows only from follicles, tiny organs buried in the skin. When a wound is deep enough to destroy them, your body…

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Munchrd: Why do bruises change colour as they heal?The Body

Why do bruises change colour as they heal?

A bruise is blood that has leaked from broken vessels under skin that is still intact, so your body has to break it down…

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Munchrd: Why do paper cuts hurt so much more than bigger cuts?The Body

Why do paper cuts hurt so much more than bigger cuts?

A paper cut lands on the fingertips, which have one of the highest densities of pain-sensing nerve endings in the body, and…

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Munchrd: Why does your skin peel after sunburn?The Body

Why does your skin peel after sunburn?

Peeling is your body shedding skin cells it deliberately killed off. Ultraviolet light, mainly UVB, damages the DNA inside…

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Munchrd: Do you lose most of your body heat through your head?The Body

Do you lose most of your body heat through your head?

No. Your head is only about 7 to 10% of your body's surface area, and it loses heat roughly in proportion to that, so you…

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Munchrd: Do you swallow spiders in your sleep?The Body

Do you swallow spiders in your sleep?

No. The famous claim that the average person swallows four to eight spiders a year in their sleep is completely made up, with…

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Munchrd: Does shaving make hair grow back thicker?The Body

Does shaving make hair grow back thicker?

No. Shaving does not make hair grow back thicker, darker, coarser or faster. A razor only cuts the dead hair shaft at the…

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Munchrd: Does cracking your knuckles cause arthritis?The Body

Does cracking your knuckles cause arthritis?

No. Cracking your knuckles does not cause arthritis. Multiple studies, including controlled research on hundreds of people,…

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Munchrd: Why can't you look at a solar eclipse?The Body

Why can't you look at a solar eclipse?

Because focused sunlight burns the retina, and the retina has no pain receptors, so you get no warning while it happens. The…

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Munchrd: Why can't you breathe and swallow at once?The Body

Why can't you breathe and swallow at once?

Because your airway and your food pipe cross paths in the pharynx. To stop food going down the wrong tube, a swallow triggers…

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Munchrd: Why do wounds itch as they heal?The Body

Why do wounds itch as they heal?

A healing wound itches because rebuilding skin is a noisy business. Mast cells release histamine, new collagen contracts and…

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Munchrd: Why do we yawn?The Body

Why do we yawn?

The popular 'low on oxygen' idea has been tested and failed. The best-supported explanation is brain cooling: a big yawn…

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Munchrd: Why do you get a stitch when you run?The Body

Why do you get a stitch when you run?

The stitch, properly called exercise-related transient abdominal pain, is a real and common phenomenon whose cause is still…

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Munchrd: Why do you get a second wind?The Body

Why do you get a second wind?

A second wind is the shift from early breathlessness to comfortable rhythm a few minutes into exercise. The most solid…

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Munchrd: Why do you get motion sick?The Body

Why do you get motion sick?

Motion sickness comes from sensory conflict. Your inner ears sense the car moving, but your eyes, fixed on a book or phone,…

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Munchrd: Why do you get pins and needles?The Body

Why do you get pins and needles?

Pins and needles come from a squashed nerve. Sitting on a limb both crushes the nerve and cuts off its own tiny blood supply,…

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Munchrd: Why does a crowd roar feel physical?The Body

Why does a crowd roar feel physical?

Because sound is a pressure wave, not a sensation. Quiet sound just wiggles your eardrum, but a stadium roar carries so much…

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Munchrd: Why does only one nostril work at a time?The Body

Why does only one nostril work at a time?

Because of the nasal cycle: spongy, blood-filled tissue in your nose swells on one side and shrinks on the other, so one…

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Munchrd: Why does your stomach drop on a rollercoaster?The Body

Why does your stomach drop on a rollercoaster?

As the car goes over the crest, you and everything inside you fall together at nearly the same rate, so your organs briefly…

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Munchrd: Why does your hair turn grey?The Body

Why does your hair turn grey?

Your hair doesn't turn grey: a single hair's colour is fixed for life the moment it grows. What changes is the follicle. As…

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Munchrd: Why can't we cure the common cold?The Body

Why can't we cure the common cold?

Because the common cold is not a single illness. More than 200 distinct viruses can cause it, and the most common family, the…

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Munchrd: Why do we get hangry?The Body

Why do we get hangry?

Because your brain runs almost entirely on glucose, and when blood sugar falls it triggers a fight-or-flight stress response…

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Munchrd: Why do you get hiccups?The Body

Why do you get hiccups?

A hiccup is a two-part reflex. First your diaphragm, the big breathing muscle under your lungs, gives a sudden involuntary…

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Munchrd: Why do you sigh?The Body

Why do you sigh?

A sigh is a double breath that reinflates collapsing lungs. Deep in your lungs, tiny air sacs slowly deflate as you breathe…

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Munchrd: Why does asparagus make your pee smell?The Body

Why does asparagus make your pee smell?

Asparagus contains asparagusic acid, a sulfur compound found in no other vegetable. Your body breaks it down into small,…

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Munchrd: Why don't we know how anaesthesia works?The Body

Why don't we know how anaesthesia works?

Because to explain anaesthesia you'd have to explain consciousness, and nobody can. We know the drugs grab specific brain…

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Munchrd: Why are humans the only animal with a chin?The Body

Why are humans the only animal with a chin?

The chin, the mental protuberance, that bony point below your lower lip, is unique to Homo sapiens, and its purpose is…

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Munchrd: Why are a few people genuinely allergic to water?The Body

Why are a few people genuinely allergic to water?

It's a genuine, extremely rare condition called aquagenic urticaria, fewer than 100 documented cases ever. Water contact…

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Munchrd: Why are some people left-handed?The Body

Why are some people left-handed?

The leading idea is the fighting hypothesis: in one-on-one combat, left-handers are rare and therefore unfamiliar, which…

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Munchrd: Why do old people have a certain smell?The Body

Why do old people have a certain smell?

It comes down to one molecule: 2-nonenal, an aldehyde with a greasy, grassy odour. As skin ages past about 40, a fatty acid…

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Munchrd: Why do we blush?The Body

Why do we blush?

Blushing is an honest signal. A social jolt fires adrenaline, and while that makes most of your body go pale, the blood…

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Munchrd: Why do we cry?The Body

Why do we cry?

Crying is almost certainly social, not a release valve. Emotional tears appear to be uniquely human, and the leading theory…

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Munchrd: Why do you get butterflies in your stomach?The Body

Why do you get butterflies in your stomach?

Your brain clocks a big moment and hits the fight-or-flight alarm, flooding you with adrenaline. Adrenaline yanks blood away…

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Munchrd: Why do you get brain freeze?The Body

Why do you get brain freeze?

Brain freeze starts when something freezing cold hits the roof of your mouth and rattles an artery at the front of your…

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Munchrd: Why do you get goosebumps?The Body

Why do you get goosebumps?

Goosebumps are a reflex. A tiny muscle at the base of every hair yanks it upright when your nervous system fires adrenaline,…

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Munchrd: Why do you have fingerprints?The Body

Why do you have fingerprints?

Not, it seems, for gripping. When researchers measured it in 2009, fingerprint ridges reduced the skin's contact area, and…

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Munchrd: Why does your body jerk you awake as you fall asleep?The Body

Why does your body jerk you awake as you fall asleep?

It's a hypnic jerk, a sudden, involuntary muscle twitch as your brain hands over from waking to sleep. As your muscles go…

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Munchrd: Why do you shiver right after you pee?The Body

Why do you shiver right after you pee?

Nobody knows for certain: there's essentially no peer-reviewed research on it. The leading guess is that emptying your…

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Munchrd: Why do some people sneeze in sunlight?The Body

Why do some people sneeze in sunlight?

It's the photic sneeze reflex, a harmless quirk of wiring. A sudden jump in brightness makes your pupils clamp shut, and that…

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Munchrd: Why do your ears and nose never stop growing?The Body

Why do your ears and nose never stop growing?

They don't actually grow. Your ear and nose cartilage stops growing in early adulthood, along with the rest of you. What…

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Munchrd: Why do your fingers wrinkle in water?The Body

Why do your fingers wrinkle in water?

Your fingers don't wrinkle because they soak up water and swell, they wrinkle because your nervous system does it…

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Munchrd: Why do your knuckles pop?The Body

Why do your knuckles pop?

Cracking a knuckle isn't bone on bone: nothing inside is touching. Pulling the joint apart drops the pressure inside its…

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Munchrd: Why does music give you chills?The Body

Why does music give you chills?

Those chills are called frisson. Music plugs into your brain's ancient reward system and releases dopamine at emotional…

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Munchrd: Why does orange juice taste vile right after you brush your teeth?The Body

Why does orange juice taste vile right after you brush your teeth?

It isn't the mint: it's a detergent called sodium lauryl sulfate (SLS), the foaming agent in most toothpaste. It temporarily…

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Munchrd: Why does swearing actually reduce pain?The Body

Why does swearing actually reduce pain?

Swearing appears to trigger a mild fight-or-flight stress response, and one side effect of that response is the body's own…

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Munchrd: Why does your stomach growl?The Body

Why does your stomach growl?

That growl is borborygmi, gas and liquid squeezed through your gut by muscular contractions. It's loudest when you're empty…

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Munchrd: Why does your voice sound different on a recording?The Body

Why does your voice sound different on a recording?

Because you hear yourself two ways at once: through the air and through the bones of your skull. Bone conduction pipes extra…

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Munchrd: Why is yawning contagious?The Body

Why is yawning contagious?

Yawning is contagious because your brain automatically mirrors other people. Watching or even hearing a yawn triggers the…

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