Why Does Blood Make Some People Squeamish But Not Others?

Faint at the sight of blood? Blame it on evolution

By Melinda Wenner Posted 02.27.2008 at 3:39 pm 3 Comments

Bloodbath If you have an overactive vasovagal reflex, you probably fainted into your popcorn during the final scene of Carrie. Everett Collection

Looking at blood can be hard on anyone, but for some people, it can be a huge problem. Up to 30 percent of children are afraid of the sight of blood, a response that usually continues into adulthood, according to the definitive study on the topic, by Isaac Marks of the Institute of Psychiatry in London. That study also revealed that approximately 15 percent of the adult population faints when donating blood.

Fainting at the sight of blood generally comes from an overactive vasovagal response, an evolutionary fear reflex. This response slows down your heart rate and lowers your blood pressure, causing blood to drain to your legs. This means that less oxygen-rich blood is going to your brain, which is what causes people to feel lightheaded, or even pass out.

This survival mechanism is nice if, say, you need to play dead in the presence of a predator, which may be the origin of the response. And if you’re bleeding, the reduced heart rate might help prevent too much blood loss. But in most situations—especially emergencies when you need to be, you know, awake—it’s a nuisance.

The more a person is exposed to the thought or sight of blood, however, the less bothersome the phobia becomes, says Alan Manevitz, a psychiatrist at Weill Cornell Medical Center in New York. This could explain why experienced surgeons deal so well with blood. This type of “systematic exposure” is a common treatment for specific phobias, and in this case, Marks suggests, it could save lives: Ill people who have overcome their fear of having blood drawn are more likely to seek medical care.

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3 Comments

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Bryan

02/27/08 at 7:27 pm

Its very simple...blood on the outside is not natural.

And in the culture we live in, we go to the Market buy our prepackaged meat without having to personally shed the blood of an animal. We know innately that life is "contained" in blood so seeing it out of a circulatory system causes some to be squeamish. As with all things whatever we see lots of we become desensitized to. Those who can "handle" seeing blood are not cold but instead know what it means and know how to handle it, they have taught their body to calm down to handle the problem.

I know what blood loss feels like it is not comfortable. In a culture that is shown lots of blood on the screen but not in real life have a interesting problem. They dismiss the blood but when they see it they are not prepared to handle it, those are the fainter's. When their screenplay hapens in front of them they just stand aghast. (they don't make good first responders)

when i was eleven i was putting the cap on a scalpel and well the blade went through the cap and into my palm. Just about everyone around me fainted, I on the other hand was like ...great someone who is not throwing up or fainted give me a paper towel.
Yeah it hurt, and my head was throbbing but i was just looking at my hand going ouch darn it why did i do that. I'm just glad the teacher kept her head on and gave me something other than my hand to stop the bleeding.

Anyhow I agree on that seek treatment part, fainted people don't typically seek treatment.... :)

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AMP13

04/07/09 at 9:43 am

Blood loss doesn't constitute as pricking your hand with an X-acto knife, Bryan. Everyone has gotten a boo boo at one point in their lives and I'm sure that everybody around them didn't faint. It's absurd that someone can faint because they saw a drop of blood. Unless you're experiencing massive amounts of blood loss, grow some balls and get over it.

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pufflegirl7

06/07/10 at 2:52 am

Me and two friends were riding bikes and I somehow managed to flip the bike and I have no idea how i cut myself but I sliced my wrist open and there was blood gushing everywhere. I actually passed out from blood loss but one of my friends started throwing up. My other friend kept her cool and called my parents but she can't bear to be around blood anymore. I swear, it really freaks her out, and I'm not exactly happy about it either. Whats up?