Called “the most peculiar and most human of all expressions” by Charles Darwin, blushing is an involuntary reaction that seems to serve no purpose beyond making an embarrassing situation even worse. However, scientists can’t seem to definitively explain this phenomenon, which is completely unique to humans.
AsapSCIENCE explains blushing as a reaction of the sympathetic nervous system and part of our “fight or flight” response. When you’re embarrassed, adrenaline is released, speeding up your heart rate and dilating your blood vessels to improve your blood flow and oxygen delivery. In humans, facial veins react to this adrenaline by blushing. But this response doesn’t happen anywhere else in your body, which is why you don’t blush all over.
Science may not be able to figure out why this reaction is so specific, but recent studies suggest that blushing has a functional purpose in social relationships. A team of Dutch psychologists discovered that people are more likely to forgive and view favorably someone who has committed an embarrassing act if he or she is visibly blushing. A test of 130 undergraduate students at the University of Groningen in the Netherlands provided each subject with the face of a blushing or non-blushing woman and a corresponding story about her “embarrassing mishap” or “social transgression.” Reliably, the blushing faces scored higher in likeability and trustworthiness.
According to these results, the act of blushing “serves to signal the actor’s genuine regret or remorse over a wrongdoing,” showing that the person recognizes the “social or moral infraction” and will probably endeavor not to repeat it. Blushing can help others predict your future behavior, assuming that you, like many others, do not enjoy being embarrassed and have learned from your mistakes. They are appeased by the involuntary act of contrition, and while you may never forget your most embarrassing moments, you can rest easy knowing that your blushing tendencies help neutralize their impact on your social relations.
If you happen to suffer from erythrophobia—the fear of blushing—you could take some drastic measures by having an endoscopic thoracic sympathectomy, which severs the nerve that triggers your blushing reflex. It seems, however, that the body has ways of showing your embarrassment even without the ability to blush, though: a common side effect of the surgery is facial sweating.