I have always wanted to donate blood, but just looking at blood sometimes makes me feel like I'm going to faint. I break out in a cold sweat and feel woozy. Oddly, it only happens when I see real blood, not onscreen blood in movies (I loved Twilight). What is causing this, and can I do anything about it?
— No Love For Blood
That is definitely a great question, and you are definitely not alone. To see why you swoon, read more.
First of all, be glad you are just feeling faint and not actually fainting, because the same causes are at the root of both responses. Fainting occurs when there is a sudden decrease in the flow of blood to the brain, causing people to feel dizzy, get pale in the face, and pass out. This reaction can be born out of fear or emotional distress as well as a drop in blood pressure.
When it comes to seeing red, the faint feelings could be tied to a phenomenon called blood-injury phobia. According to WebMD, this condition evolved as a way for humans to cope with threats:
"The idea is that back in time, when someone was coming at someone else with a sharp stick or rock, a kind of genetic variation allowed certain people to faint in response," explains Tyler C. Ralston, PsyD, a clinical psychologist in Honolulu, who treats people with blood-injury phobias. Warriors who fainted looked dead and were passed over during battle. The blood pressure drop also might have helped those who were wounded avoid bleeding to death. Survivors then passed on the "fainting" gene.
The good news is, this psychological condition can be treated by a therapist, rather than drugs or a medical procedure. WebMD recommends finding a psychologist trained in treating phobias who can help you develop relaxation techniques to fight the faint. Fascinating, right?