Dr. Stephanie James, Associate Professor, Regis University: If you want to hear something really gross, I mean, we produce one to two quarts of mucus a day and usually we just swallow it and we never know it.
CNN Correspondent: Super gross! but Dr. Stephanie James, who studies how cells respond to viruses, points out 3mucus is always there, part of our immune system, 4trapping 5invaders like viruses and bacteria.
Dr. Stephanie James: And then we swallow it where the 6enzymes in our stomach basically can destroy it and we can get rid of it.
CNN Correspondent: But when one of those invaders starts to cause an infection in and around our nose, our cells there release these chemical messengers.
Dr. Stephanie James: What they're trying to do also is recruit 7immune cells to the site of this 8infection.
CNN Correspondent: And that can cause things called 9goblet cells to release even more mucus. Plus, they also tell the 10blood vessels up there to become 11leaky.
Dr. Stephanie James: So, some of the 12watery 13secretions that are actually in our blood vessels can then get into that 14nasal cavity. They also become swollen.
CNN Correspondent: All of that can make you feel like you have a stuffy nose. Oh, and by the way, the color of your snot, well, if it's yellow or green, that may be because of a buildup of immune cells and other things to fight an infection. But scientists say the color can't tell you whether it's a virus or bacteria that's making you sick. And while all of this is annoying, just remember, the next time you're reaching for the tissues, you're also seeing your immune system at work. And that's everyday science.
