Eli5: Why do our faces pale when we faint?

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Eli5: Why do our faces pale when we faint?

In: Biology
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Answer: it has to do with a (more or less) sudden drop in blood pressure and the decrease in blood flow to the brain.

There are three broad types of syncopes (that’s the fancy medical name for fainting), but they all have to do with blood pressure one way or another.

There’s one where a person with already low blood pressure stands up very fast, and the blood pressure further decreases, and the fainting happens.

Another type (probably the most well known) is the one that happens after seeing a trigger like blood, vomiting, something shocking etc. What happens here is that the heart rate decreases suddenly, leading to decreased blood flow to the brain.

Third type is related to heart issues, whether that’s an irregular heart beat, valve problems or blood vessels being blocked.

Point is, less blood getting to the brain (and generally the head) will mean less “color” gets to the surface of our skin, thus the pale look.

edit: forgot a word lol

Your face doesn’t pale *because* you faint, or vice versa. Both are symptoms of the same thing: A sudden reduction in blood flow to the head. As you may be aware, blood is red. Your skin, meanwhile, is probably a colour, and if it isn’t a colour, you may have accidentally misplaced it. More importantly, it’s partially transparent, so the red of the blood that flows through your face-meat is partially visible through your skin and gives the appearance of making your skin darker.

Blood also has another job besides making you look less like a corpse: it supplies oxygen and nutrients to the brain. Should the brain not get enough of either of those things, then it will stop working properly and may temporarily fail to produce the experience of being conscious – you may faint. When blood flow is suddenly reduced in the head, the face becomes paler because there’s less redness behind it, and the brain becomes unconscious-er because there’s less oxygen and sugar reaching it.