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When you have a cold or allergies, it can sometimes feel like you have an endless supply of snot. And no matter how many times you blow your nose, you can't seem to get rid of it.

Indeed, the body is constantly making mucus, said Dr. Richard Lebowitz, an ear, nose and throat doctor at New York University Langone Medical Center. As soon as you sneeze some of it out, the body makes more, he said.

Mucus is made by mucosal glands that line the body's respiratory tract, which includes the nose, the throat and the lungs, Lebowitz said. [What Your Snot Says About You (Infographic)]

Most of the mucus that people sneeze out comes from the mucosal glands lining the nasal passages, Lebowitz said. People often think it's also coming from their sinuses, but in fact only a very small amount of mucus is produced in the sinuses, he said.

When people say they are "clearing out their sinuses" by eating spicy food or using a neti pot, they're really just clearing out their nasal passages, he added.

The respiratory tract produces more than a liter (33.8 fluid ounces) of mucus a day, Lebowitz told Live Science. And when things are working properly, your body is pretty good at getting rid of it, he said. The mucus in your nose, for example, is moved to the back of the nasal passages and then into the throat by tiny hairs on nasal cells called cilia. And from there, you gulp it down.

That's right — you're swallowing your snot all day, every day. You just don't notice it.

But when you're sick, your snot might be thicker, or that mechanism that normally clears it might not work well, Lebowitz said. Or, your body might be making a bit more mucus, he said. When these things happen, you start to notice how much snot there is, and it can indeed seem like an endless supply, he said.

And sometimes, a person can blow his or her nose to no avail, and still feel stuffed up, Lebowitz said. In this case, the problem is not the mucus itself but rather that the lining of the nasal passages may be swollen, thus blocking it up, he said.

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