Why do we get brain freeze, hiccups and goosebumps? Everyday body questions answered
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Some of the strangest things your body does are also the most ordinary. A spoonful of ice cream gives you a stabbing pain behind the forehead, a fizzy drink sets off a run of hiccups, a song makes the hair on your arms stand up. None of these is a silly thing to wonder about, and the explanations are more interesting than you might expect.
Brain freeze
The medical name is a mouthful: sphenopalatine ganglioneuralgia, or more simply a cold-stimulus headache. It happens when something very cold touches the roof of your mouth or the back of your throat.
The most widely accepted explanation goes like this:
- The cold narrows blood vessels in the palate very quickly.
- They then widen again almost immediately as warm blood rushes back.
- A large nerve nearby, the trigeminal nerve, picks up this sudden change and reports it as pain. Because the same nerve also serves the face and forehead, the brain places the pain there rather than in your mouth.
Researchers have not completely settled the details, and some point to a cluster of nerves at the back of the palate instead. What is agreed is that brain freeze is brief and harmless. Eating cold food more slowly helps, and pressing your tongue against the roof of your mouth warms the area and often eases it within seconds. Children and people who get migraines seem to be more prone to it.
Hiccups
A hiccup is an involuntary spasm of the diaphragm, the dome-shaped muscle under your lungs that does most of the work of breathing. Each spasm pulls in a sudden breath, and a fraction of a second later the vocal cords snap shut. That closing is the hic sound.
Common triggers include:
- Eating or drinking too quickly
- Fizzy drinks and alcohol
- Big meals that stretch the stomach
- Sudden excitement or stress
- Swallowing air
Nobody is sure what hiccups are for. One idea is that they are left over from early development, since babies hiccup a great deal, even before birth.
As for cures, there is little solid evidence for any single trick. Holding your breath, sipping cold water, or breathing into cupped hands are all harmless and work for some people, perhaps because they change your breathing rhythm. Most bouts stop on their own within minutes.
When to see a doctor: NHS guidance is to see a GP if hiccups last longer than 48 hours or keep coming back and are affecting your life. Long-lasting hiccups are rare, but they can occasionally be linked to a medical condition or a medicine, so they are worth checking.
Goosebumps
Under your skin, each hair has a tiny muscle attached to it called the arrector pili. When it contracts, it pulls the hair upright and puckers the skin around it into a small bump.
In furry animals this reflex is useful:
- Warmth. Raised fur traps a layer of air that holds in heat.
- Looking bigger. A cat with its fur on end looks larger and more threatening to a rival.
Humans have lost most of their body hair, so the reflex no longer does much for us, but it has stayed. It is controlled by the same part of the nervous system that handles the fight-or-flight response, which is why goosebumps appear not only when you are cold but also when you are frightened, moved by music or awed by something.
A few quick extras
- Why do we yawn? Nobody knows for certain. Theories include cooling the brain and signalling a change of state, such as waking up or winding down. Yawns are famously contagious, even reading about them.
- Why do fingers wrinkle in the bath? It is not simply waterlogging. The wrinkling is controlled by nerves, and people with certain nerve damage do not wrinkle. One theory is that it improves grip on wet things, though this is still debated.
- Why does your foot go to sleep? Pressure on a nerve interrupts its signals for a while. Pins and needles are the nerve waking up again once you move.
Most of these quirks are harmless. If any of them becomes frequent, painful or unusual for you, a GP or pharmacist is the right person to ask.
Which everyday body mystery have you always wondered about? Ask in the comments.