Green Snot

If you have green snot, you need an antibiotic

We’ve attempted to cover this one before, but it’s one of those pervasive myths that we just keep having to dispel. Plus, many of you (even the doctors among you) are convinced that the color of snot is the key to knowing just how sick you are. And you’re probably convinced that green is the worst color, the one that means infection, and that requires an antibiotic.

Let’s start with some basic facts. What makes snot turn green? You might think that working with snot would be so disgusting that no one would ever do it. You’d be wrong.

When you have an infection, the body sends off neutrophils—a type of white blood cell—to fight the infection. So if you have an infection in your nose, it’s likely there are more neutrophils present in your nasal passages than usual. These cells work by (for lack of a better description) eating the germs that make you sick. Once they have swallowed or engulfed the germs, the special white blood cells keep the germs in what serves as their “stomachs,” and they digest them. One of the enzymes that the white blood cells use most often to digest the invader germs is called myeloperoxidase, and myeloperoxidase has a fair amount of iron in it. (This is important as we continue with the germ-eating story.)

Once the neutrophils get full of digested germs, they burst. The iron in the myeloperoxidase gets mixed into the surrounding stuff in your nose. And when you mix iron into that stuff, guess what color your snot turns? Green.

Notice we said nothing about bacteria here. That’s because this works exactly the same for viruses or bacteria. It doesn’t matter which of the offending germs are in your nose. Whether bacteria or viruses have invaded doesn’t affect the iron in the myeloperoxidase in the neutrophils, and that is what makes your snot green. So you may have green snot with a bacterial infection, but it also may not be bacterial. The green does not tell you if it’s a bacterial infection. And only bacterial infections need antibiotics.

This hasn’t stopped the battle from being waged, however. Even though this issue has been around for a long time, doctors still vehemently disagree as to whether antibiotics have any effect for conditions with green snot. A lot of doctors, perhaps most doctors, are much more likely to give you an antibiotic if you tell them your snot is green. But even the authors of a study finding a small link between antibiotic use and feeling better say that you shouldn’t use antibiotics routinely for green snot. There may have been people with sinusitis in that study, and some of them included people with green snot for almost a month. It’s a hotly debated piece.

The bottom line is that you can tell almost nothing about the bug infecting you from the fact that you have green snot. Antibiotics will do nothing for you if you have a viral infection. And many studies confirm that antibiotics are associated with side effects. If an antibiotic is not going to help you and might cause a bad side effect, then you want to avoid using one. If you are sick, you should talk with your doctor about whether treating your infection with antibiotics might cause more good than harm, but do not let the greenness of your snot sway the decision.