Transcript
A (0:04)
Hey, there. Welcome to Paging Dr. Gupta. This is the place where you get to ask your health questions, share your concerns, and hopefully get some real answers, some real news you can use. Our producer Jesse is with us today with some brand new questions from the inbox. Jesse, who's up first?
B (0:20)
Hey, Sanjay. We got a couple of questions we thought might be fun with Halloween being this week. The first is from Heidi in California. Check it out.
C (0:29)
I've always wondered this. What happens in the brain to make some people fear blood and others don't? For example, I can't really get my blood drawn. Or if I cut myself, I get queasy. Sometimes I pass out, sometimes I curl up. But then I have a friend or a family member who can look at themselves while they get their blood drawn. And they don't share blood at all. So what happens with the brain that makes some fear it and some don't?
A (0:55)
All right, thank you so much, Jessi, and thank you, Heidi. Perfect timing with this question with Halloween coming up, my favorite holiday. Yes, blood is everywhere this week, but some of us react way more strongly than others. And I love this question because what it fundamentally does is get to the heart of how our brains and bodies process certain fears and anxieties. So we're gonna have some fun, and I'm gonna break down the neurobiology for you right after the break.
C (1:31)
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D (1:59)
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A (2:33)
We are talking about why some people fear blood so much that the sight of it can make them pass out. Well, first things first. An aversion to blood is normal for just about all humans. That's why horror movies are so successful. But the extreme fear of blood that Heidi is asking about actually has a name. It's called hemophobia. HEM stands for blood, phobia stands for fear. It is part of a broader category called blood injury injection phobia. BII. Now, BII affects about 3 to 4% of the general population. It includes a fear of needles and injuries and medical procedures. It is sort of a unique phobia for a few reasons. If you think about most phobias, like arachnophobia, that's a fear of spiders. What happens is just seeing the trigger. Seeing the spider, in this case, causes a typical sympathetic hyperarousal. In other words, fight or flight, increased heart rate, blood pressure. A BII response, on the other hand, sort of seems to have two phases. First, a short burst of hyperarousal, a temporary surge in heart rate and blood pressure, like other phobias. But that phase is then followed by a dramatic crash in both blood pressure and heart rate. And that is why people faint, because there is a sudden decrease in blood flow to the brain. It occurs when the vagus nerve, which controls, among other things, heart rate and blood pressure, is overstimulated. Now, this unique physical reaction triggered by BII suggests that the brain processes this differently from other phobias. And brain scans have backed this up. There was a study from 2009 which compared how people with BII reacted to seeing blood versus how people with arachnophobia reacted to seeing spiders. So when the spider phobic people saw spiders, their brains lit up, and in the amygdala, that's the brain's central emotional and fear hub. But that did not happen for people with bii. Instead, their brain showed more activity in areas tied to vision and attention, like the thalamus and parts of the occipital temporal cortex. Now, answering exactly why hemophobia impacts some people and not others, that can be tricky. There might be a genetic link. Sex might play a role. Some studies have found a higher prevalence among women. Some people have theorized that fainting is, in fact, an evolutionary defense mechanism. The idea being that fainting and then falling horizontally is a way to restore blood flow to the brain in case of major blood loss. I thought that was kind of fascinating. But, Heidi, whatever the reason, if you have hemophobia or bii, here's a trick that can really help you. The applied tension technique. So, sit in a comfortable chair and tense the muscles in your arms, legs and trunk for about 10 seconds. Hold the tension until your head starts to feel a little warm. Then relax your body for 20 to 30 seconds. Repeat that five times. That'll increase your blood pressure a little bit and hopefully prevent fainting. Might be a good idea to practice this a few times a day ahead of the appointment. And remember, while the goal of many phobia related therapies is to help you relax, that's not necessarily the goal here. Right, because feeling too relaxed might mean that your blood pressure is even lower, which would make you even more likely to faint. Alright, time to take a quick break. But it wouldn't be Halloween without talking about sugar. Coming up, I'll tell you about the potential pitfalls of artificial sweeteners. We'll be right back.