Do You Faint at the Sight of Blood?

If you are freaked out by needles, join the club.

Posted Oct 20, 2015

"The Vampire" by Philip Burne-Jones, public domain.
Source: "The Vampire" by Philip Burne-Jones, public domain.

"Phobia" is defined in the dictionary as "an extreme or irrational fear of, or aversion to something." That's me with a hypodermic needle, and apparently I am not alone. A recent newspaper article suggests that a surprising number of us, when faced with a needle, break out in a cold sweat––or worse, lose consciousness.  

It's the same with blood. I can't watch my own blood being drawn for my annual physical exam, for instance, but I can watch other people having the same procedure without keeling over. Maybe it's the combination of (a) a needle being put in my arm, and (b) the sight of my own blood filling those little vials that does it.  Some people who faint at the sight of blood, according to the article, can watch gory movies with no adverse reaction.

Why is that? My guess is, at least in the case of a gory movie, that we know the blood being spilled on the screen is not genuine. Fake blood doesn't have the same frightening effect as the real thing.

The science of this phenomenon has to do with something called a "vasovagal reflex," which in the case of those of us who have extreme reactions to blood and needles, means that we are wired with an unusually powerful vasovagal reflex. The reflex may be triggered by other things besides fear and anxiety. Even standing up for a few hours in church or on the parade ground can cause the brain to send a strong signal down the vagus nerve, resulting in fainting.

Now it really gets scientific, and please bear with me if I get it wrong. To quote the newspaper article's source, one Dr. Joshua Cooper of Temple University, the vagus is the longest of the 22 cranial nerves, running down the neck and branching through the body to the heart and blood vessels. Following a rush of adrenaline that makes the heart beat faster and the blood pressure rise, the brain may react by sending a message down the vagus nerve to slow the heart rate and drop the blood pressure. But things can go wrong, apparently, even in this seemingly perfect autonomic system. Sometimes the brain overdoes it, causing the blood pressure to drop too low and the heart rate to slow too much. The result: fainting.

You would hardly think it, but even some doctors and health care workers are prone to the same response as the rest of us when faced with needles and blood. Case in point: doctors who don't get regular flu shots, even though common sense tells them they should, because they can't look at a hypodermic needle without passing out. I feel for them. (I've never had a flu shot.)

Of course you can't always refuse an injection of one kind or another. I recently landed in the emergency room of a local hospital with a gash on my hand that required half a dozen stitches. Seeing the cut bleeding wasn't so bad, but watching the doctor jabbing me several times with anesthetic to numb the area around the wound sent my heart racing, and the next thing––a tetanus shot in the arm––made me feel dizzy. To keep from passing out, I tried engaging the affable ER physician in conversation about people who regularly use needles, such as heroin addicts, for example. How can they stand it? Oddly enough, he said, even addicts are prone to the same quirk in their autonomic system.

Vagus nerve or no vagus nerve, it's still not clear to me why I feel faint when I am not actually afraid––only apprehensive. The doctor may say "This won't hurt a bit," and I know instinctively that he's right, but it's not the anticipation of pain that causes the problem. It's the sight of the needle that freaks me out.