Why Do We Turn Green When We Get Sick?

You’ve seen it in cartoons and pop culture before; that thing when people turn comically green and then cover their mouths because they’re about to vomit. It’s also an emoji you use either all the time, or never at all. Not too many people turn that green, it’s mostly a paleness mixed with clamminess. But there’s enough in there for us as a collective to agree that “green” is just an okay color to attribute here. So what’s up with that, why do we turn green when we get sick?

Our Snot Also Turns Green

Snot isn’t really “you,” but part of the green-being-sickly as a cultural touchstone probably also has to do with our snot. When we’re noticeably sick and blow our noses, our snot is a lot thicker and greener. This is owed largely to an enzyme called myeloperoxidase. It is used by neutrophils (a type of white blood cell) to kill bacteria. Without getting too far into the chemical reactions of myeloperoxidase, the enzyme produces acids that are toxic to cells. 

Your snot is also getting thicker because there’s just a lot of… extra stuff in it so to speak. Like dead cells. No really, most of the green comes from dead white blood cells and other cellular “debris” being expelled from your body. So on the bright side, it means your immune system is doing the right thing. 

Myeloperoxidase also has an important role in the inflammation of your body when you get sick. Because it’s just generally toxic to cells, the enzyme doesn’t really discriminate between killing foreign things and you-things. That’s kind of unfortunate for you, as myeloperoxidase can make inflammation-related injuries worse in this context. But being deficient in myeloperoxidase can also exaggerate the inflammatory response (IE you swell more), and so it seems to have a mediatory role as well. 

Green in the Face

Turns out, the human brain is super sensitive to how faces change color. So that’s probably why, despite “going green in the face” being probably more subtle than, say, blushing red, we still agree on it as a common experience. We are also exceptional at detecting whether or not people are feeling sick based on their faces. Which makes sense, since being around sick people gets you sick; the best way to avoid being sick is to avoid sick people. 

The green-ness of being sick is typically associated with nausea. When we get nauseous, it’s probably because there’s not a lot of blood going to our heads—resulting in that dizzy feeling. That’s why we look pale too, our oxygenated blood being red is a big reason why our skin is pinkish. When the brighter-red blood closer to the surface of our skin has retreated to other parts of the body, we get pale and clammy. What’s left is the darker blood in our veins, which look blue. The greenish appearance some people develop, then, comes from the lack of apparent redness in the skin mixed with the accentuated blueness. 

Further Reading: Why Are Veins Blue? | Does Blood Change Color Like That?

Hypochromic anemia is a condition in which your red blood cells are paler than usual. This is because they have less hemoglobin in them than they should—hemoglobin is the iron-rich compound that gives red blood cells their color. When the red blood cells pale like this, some people can also develop a greenish complexion. 

Speaking of feeling ill, see if you know your presidents by ailment here.