Why Do Some People Faint When They See Blood?
Red Blood Cells Illustration National Cancer Institute It's a phobia, but other phobias don't give you that same woozy feeling. Getting dizzy and fainting at the sight of someone else's blood doesn't seem to be the most, uh, evolutionarily appropriate response. How's that going to help you when you're trying to take down a buffalo? And despite it being relatively common--3 to 4 percent of people suffer from blood phobia or a related disorder--the symptoms of it are totally different from most phobias: phobics' blood pressure and heart rate will rise then drop when they see blood, as opposed to the just-heart-racing caused by most fears. So what gives? John Sanford at Stanford Medicine has a great (and personal) breakdown. Here's what that fainting/nausea/dizziness response is: This is a vasovagal response. The vagus nerve, a component of the parasympathetic nervous system, meanders from the brain stem through the neck, chest and abdomen....