Why do we blush? We blush in response to emotions such as embarrassment, stress, and shame. Why we blush is a much more difficult question than how we blush, so let’s look at that first.
How we blush is fairly straightforward. The red color of a blush is brought about by the dilation of blood capillaries in the skin. When they dilate, there is an increased flow of blood, and they get pushed closer to the surface of the skin. That allows the color of the blood to show through the skin. I say the color of the blood, but it is actually the color of the hemoglobin in the blood. Blood itself is mostly plasma, which is a pale yellow color. Generally, when our skin darkens and becomes red, or gets pale and becomes blue, it is caused by an increase in the flow of blood or a decrease in the flow of blood. When we are very cold, we can become blue. That is because the hemoglobin is red when it is carrying oxygen and more blue when it has no oxygen. When you are cold, the body constricts blood vessels in the skin to preserve heat, and this reduces the oxygen delivery. The non-oxygenated blood scatters light differently and looks blue. We go pale when we are scared because the body activates its flight or fight mechanism, and blood is diverted from the skin and the extremities towards the core. This is to prevent blood loss in the case of injury and provide more oxygen to the systems that will be needed to fight or fly.
The blush response is triggered by the sympathetic nervous system, which is the same part of the brain that triggers our fight and flight response. The sympathetic nervous system is involved in many bodily processes, such as body temperature and blood glucose levels, but its main job is our fight or flight response. Blushing is triggered by a similar stimulus to the fight and flight response, but it is a far less severe response. When we experience whatever emotion has embarrassed us, the sympathetic nervous system triggers the release of adrenaline. Adrenaline speeds up the heart rate, speeds up breathing, dilates the pupils, slows down digestion, and makes the blood vessels dilate. In the case of blushing, it only affects the blood vessels in the face, neck, and upper chest. All of these things explain the sensations you get along with blushing. There are often butterflies in the tummy, which come from the digestion slowing down, a slight dizzy feeling, which comes from the increased heart rate and breathing rate, and the heat of the blush, which comes because the blood vessels have dilated, releasing heat into the surrounding skin.
Blushing mainly affects the face because we have far more blood vessels in our face that are closer to the surface than anywhere else on our bodies. That is one reason why facial injuries bleed so much. These blood vessels are more affected by adrenaline, which triggers an enzyme called adenylyl cyclase to produce cyclic AMP, which makes the blood vessels dilate. On top of that, the surface and tissue of our face are much thinner than other parts of the body, so the red color shows through far more easily.
Why we blush is a far more complicated question with no clear answer. Just like why we laugh, anthropologists can only really guess at what the reason might be. Because almost all of us blush, we can think that there is an evolutionary reason for it. That doesn’t always follow, and we have many things that don’t benefit us evolutionarily, but more than likely if a trait is human wide, it has a reason. The most likely reason for blushing is that it helps us live together more effectively in a society. Humans are social beings, and since our beginnings, we have lived in groups. We are not powerful enough to hunt or survive on our own, but in a group, we become formidable.
To live in a group, you need to be able to follow social rules, and you need to know that other people are following the same rules. We get embarrassed when we don’t follow a social rule, and we blush. The feeling of blushing is uncomfortable, so we learn not to break that social rule again. And other people can see that we realize we have broken the social rule and feel bad about it. Blushing helps us live together as a unit. Blushing doesn’t really help individuals; it helps the group. Blushing could be our version of when animals roll over to expose their stomachs, or tuck their tails between their legs. We are showing that we are sorry and want to make amends. And this is what I learned today.
Sources
https://science.howstuffworks.com/blush.htm
https://en.wikipedia.org/wiki/Sympathetic_nervous_system
https://en.wikipedia.org/wiki/Blushing
https://www.theswaddle.com/the-science-behind-why-we-blush
https://www.bodyworlds.nl/en/blog/why-do-we-blush
Photo by Sanket Mishra: https://www.pexels.com/photo/portrait-of-man-covering-face-in-distress-34014593/