Faiting at the sight of blood -- runs in families?

August 4, 2005 9:34 PM

Any MeFites around who faint at the sight of blood? If so, are you aware of any close relatives who do the same?

I was thinking about this the other day, and it struck me that fainting at the sight of blood is such a distinct phenomenon, one that starts from an early age (at least, according to the folks I've spoken to thus far), and thus, perhaps there's a genetic basis to it. It reminds me of ACHOO syndrome -- involuntary sneezing after coming into bright sunlight, which has shown to be heritable.

Not that I think I'm going to get any funding to study this, but I'm curious if the fainting reflex is heritable too, and what might be the physiological basis behind it.

posted by greatgefilte to health & fitness (19 answers total)

As someone who has spent a lifetime drawing blood (the regular phlebotomy way, not as a vampire or anything), I know the physiologic basis - it's a sudden dilation of the vascular system, which causes systemic blood pressure to drop and the person to faint. It's the same reaction as someone fainting because he's received horrible news or a great psychological shock, which I've also unfortunately witnessed. They're exactly alike in presentation.

I've never fainted like that, and it doesn't run in my family or my husband's family. So we were very surprised to figure out that my daughter does faint when she sees blood. She has done it since she was a toddler. And I'm not talking about a lot of blood, either - a paper cut will do it.

I'm not sure how it started, but both her parents have worked in prehospital medicine and aren't very squeamish, so she didn't get it from us or from our parents. Her older brother doesn't show a sign of it. So now that you're thinking it could be hereditary, I'm really confused. ;)
posted by lambchop1 at 12:05 AM on August 5, 2005

My father, while not fainting at the sight of blood, comes damned close. He probably has in the past, I'd bet. I do not have serious problems at the sight of blood. Blood donation occasionally makes me feel weird, but it's usually in a more detached way: "Hey, there's my blood!"
posted by RikiTikiTavi at 12:11 AM on August 5, 2005

Most women can't afford the luxury of being disturbed by their own blood. I wonder if most people make a distinction between being squicked out by their own blood vs others'? I definitely do (because of the aforementioned, well, femaleness), and my fella says he does too, actually, despite not being female.
posted by librarina at 12:41 AM on August 5, 2005

I don't faint at the sight of other people's blood, but seeing mine in quantities larger than a pinprick will make me woozy though the feeling quickly passes.

I always say it's because I've got just enough blood to make the system run and there is none to spare...

So far as I know, none of my relatives faint at the sight of blood (theirs or otherwise).
posted by madajb at 12:53 AM on August 5, 2005

Im very squeemish, and feel faint sometimes if I see something gory.

The way my docter described it was that when you see something that gets to you, be it blood or whatever, your blood pressure drops a certain amount. It happens to everyone, but if your blood pressure is only hovering at just the right level to keep you standing, you cant take much of a drop before you collapse.
So yeah it can be related to blood pressure which can be hereditory. Of course theres a lot of other factors that go into your blood pressure reading.

Thats just what my docter told me to make me feel like less of a wuss..
posted by phyle at 12:56 AM on August 5, 2005

Just following on from Lambchop1, although everything is genetically based one way or another of course, a psychophysiological shock causing fainting is such a complex phenomenon, that it's unlikely to be teased out as being particularly associated with say 1 or 5 or even 10 discrete genes for instance. You might inherit a certain profile of neurovascular response genes from your parents but isn't it more likely that you're upbringing (and attitudes and behaviour instilled by your parents) and exposure to distressing life episodes will dictate how you develop a reaction such as fainting? That's just my opinion of course. Perhaps some people are predisposed like say alcoholism and socialization will direct whether it manifests.

Blood doesn't worry me, whether mine or someone elses and I've experienced both sides to significant extents. Just about all my family have worked in medical related fields (inherited? Unlikely) so thankfully none have experienced this reaction. I daresay we all have overt reactions such as wooziness and the like when our particular kryptonite sensitivities are razzled.
posted by peacay at 1:20 AM on August 5, 2005

If I may rock the boat, what exactly is the purpose of our bodies dropping blood pressure in response to anything?
posted by Dean Keaton at 2:40 AM on August 5, 2005

Dean Keaton there's no purpose for it, answering literally - it's merely a reaction. A normotensive state is required to keep all our cells oxygenated. We have muscular/neurological reulatory systems that operate to maintain this normal blood pressure state.

The drops in blood pressure we may experience (when we are otherwise healthy) can come about due to (a) overstimulation of one of these systems --- like the fainting response to seeing blood, in which the brain reacts* to this personally significant shock by telling blood vessels to dilate, causing a drop in pressure --- or (b) a lag in a regulatory system coming into play, such as when we stand up suddenly. Gravity causes blood to pool in our legs, thereby dropping our blood pressure and sometimes causing us to be dizzy, until the brain responds to this drop by telling the muscles around the leg veins to constrict, forcing blood to return to the heart and raising the pressure back to normal and stopping the dizziness.
So if you get dizzy when you stand up, bend your legs a few times to help raise your blood pressure.
*So answering the poster's question means accounting for just why some people react in this way - genetics/conditioning or a combo (my vote).
posted by peacay at 4:42 AM on August 5, 2005

Maybe blood pressure drop is in anticipation of the fight-or-flight system kicking in? To Blood vessels widen in preparation for increased blood flow? If that flow doesn't arive, then instead of the two reactions balancing out, you're left with blood pressure that's way too low.

From what little I know of aerodynamics, things moving do end up with lower pressure than not (which is why wings work, the lower pressure above sucks the wing upward), or maybe this is more related to a straw - the wider it is, the quicker blood can get where it needs to - so widening the blood vessels might make sense...

But then I'm neither a scientist nor a doctor :) so these are pure guesses.
posted by lorrer at 5:17 AM on August 5, 2005

The medical term is vasovagal syncope. Searching on "vasovagal syncope genetic" at PubMed returns this paper.

My mother has this condition. She passed out when my sister got stitches, for example. It makes her uncomfortable when people just talk about injuries, and there's no way she can watch a show like ER. Her closest relatives - her mother, her brother, and me and my sister don't exhibit this behavior though.
posted by mbd1mbd1 at 5:40 AM on August 5, 2005

Like madajb, I go woozy at the sight of my own blood. Other's blood doesn't affect me.

And let's not even go near the subject of needles. The combination of the two is pretty much the reason I don't give blood. I will pass-out if that needle so much as touches my arm.
posted by Thorzdad at 5:53 AM on August 5, 2005

I'm female, and I do get woozy very easily. However, it's often a delayed reaction. If there's an emergency because someone is hurt, I can competently deal with the situation, get help, and then once it's all over (and the blood is all gone), I reliably go into mini-shock (woozy, cold, sweaty, dilated pupils, rushing sound in the ears, nausea).

If there's nothing to worry about with respect to "getting help", I can reliably be woozy right from the start. I'm okay with movies and tv shows because they're not real, but show me a first-aid textbook with photos and I'm done.

Doesn't show up in my family at all, but they're a lot more sensible than I am.
posted by some chick at 5:58 AM on August 5, 2005

I've been told that it is also common when you're hand is injured, seeing blood on your hand/s. I cut myself on my right hand and was surprised that immediately I felt faint. I was told not to look at it, that it happens to everyone. It was such a small cut and I felt like such a wuss for being faint, but it's something to do with something that is such a center of your life appearing changed is a complete shock, and there's no way to logically process it.
posted by scazza at 8:10 AM on August 5, 2005

Put me in the same boat as Thorzad. In fact, reading this thread has made me a little bit woozy (I am not joking). I can, however, manage to get blood drawn now as long as I concentrate really long and hard about the good reasons that it needs to be done. I cannot, however, look at it happening.

Does it run in the family? Absolutely not. My brother was the top Plasma giver in college as a way to supplement beer money. I went to get the blood test to see if I qualified and, to the consternation of the nurse, promptly passed out in her lap.
posted by dhacker at 8:13 AM on August 5, 2005

I can't even read this thread without feeling squicky.
posted by matildaben at 8:35 AM on August 5, 2005

It's definitely only my own body and blood that affect me. Among other incidents, I passed out in the doctor's office just having a TB screening. I almost fell down and hit my head just from cutting my thumb making dinner. Luckily my mom was around. It worries me what might happen if I was ever alone and hurt myself seriously. It's frustrating and extremely embarrassing to be this way, because I have no control and it's an almost instant reaction.

And yet the injuries of others are a non-issue. I've had wilderness first aid training, considered being a rescue diver, and several of my close relatives are doctors and nurses. I've even donated blood many times, and as long as I don't actually look the blood leaving my body, the mental knowledge doesn't bother me. Similarly menstration is not an issue. Maybe because I know it's okay and not an injury? But I can't even watch my finger getting pricked without feeling woozy, it's ridiculous.

As far is it running in my family, a couple of my great aunts and uncles on my mother's side had similar difficulties, but no one in her or my generation.
posted by nelleish at 8:54 AM on August 5, 2005

Reading this thread makes me woozy, so I stopped mid-way down, sorry if I'm seconding any responses in the process...

My mother is a nurse. She's seen it all, no problems. My sister also has absolutely no bad reactions to injuries, she was an accident prone terror as a little kid and loved picking at scabs and wounds.

The thought of needles, blood, anything medical really totally makes me woozy, to the point where I once passed out onto an old woman while standing in the line for a flu-shot.

I've been told that it's a Vasovagal reaction.

/me runs away now
posted by togdon at 9:55 AM on August 5, 2005

My dad and I both faint at the sight of blood -- usually other people's. We're also fairly squeamish when it comes to graphic depictions of surgery and gore in various media, he more so than I. Neither my mom nor my brother have this reaction.
I don't feel faint at the sight of my own blood, oddly enough. The thought process is more along the lines of "I should get a bandage..."
posted by Lycaste at 8:01 PM on August 5, 2005

The way my doctor described it was that when you see something that gets to you, be it blood or whatever, your blood pressure drops a certain amount. It happens to everyone, but if your blood pressure is only hovering at just the right level to keep you standing, you cant take much of a drop before you collapse.

I have low blood pressure and consistently deal with emergencies perfectly well. The aftermath is pretty hard, but the actual emergency is fine (thanks to my friend "adrenaline.") My mother is a nurse who is totally cool with any kind of emergency, but my father freaked out when any of his kids needed a blood draw...
posted by kamikazegopher at 10:10 PM on August 5, 2005