The Wonders of Mucus and Phlegm

​Mucus has several names.  Snot the goo that pours from your nose during a cold.  Or phlegm, the gunk that can clog your lungs and make you cough.  But mucus is so much more than a runny nose.  Your body constantly creates mucus, which is essential in keeping you healthy.

The Wonders of Mucus and Phlegm
By Pierre Mouchette | Bits-n-Pieces

Mucus and phlegm have a terrible reputation!  Most people believe it is something you are supposed to cough up and get out.  But mucus is the interface between you and the outside world.  The facts:  mucus lines the moist surfaces of your body like the lungs, sinuses, mouth, stomach, and intestines.  Even your eyes are coated with a thin layer of mucus.  Mucus serves as a lubricant to keep tissues from drying out. 
Mucus is a line of defense for our body.  It filters out materials you breathe through your nose, such as dust, allergens, and microorganisms.  Anything that you breathe in gets stuck in the mucus, like flypaper.
 
Mucus at Work
Everyone inhales thousands of bacteria as a normal process of breathing.  But you will never know it because bacteria land on the mucus-lined surface of the lungs and get trapped.  Then little hairs called cilia go to work, pushing the mucus up and out of the lungs with all the trapped bacteria, viruses, and dust.  It comes up slowly to the back of the throat, and you never feel it under normal conditions.  You swallow it, and the mucus, bacteria, and other trapped substances go to the stomach and eventually pass out of the body.
Your body makes much mucus, although no one knows how much.  Mucus is mostly water but contains particular proteins, sugars, and molecules that help the body control harmful germs.  Usually, you are not aware of all the mucus that slowly flows through your body.  That is until you get sick.
 
Too Much Mucus
You usually only notice mucus when making too much of it or if it changes consistency.  An infection can make mucus thicker and stickier.  Infections also lead to inflammation in the mucous membranes that line the nose and the rest of your airway, causing certain airway glands to make more mucus.  That mucus can get thick with bacteria and cells that arrive to fight the infection, which can stimulate even more mucus production.
When mucus is excessive, it can be bothersome regarding a runny nose, clogged nose, and post-nasal drip.  Post-nasal drip is when excess mucus from the back of the nose gathers and drips down the back of the throat, a common cause of a cough.
Allergies can also cause your body to make extra mucus.  When you have an allergy, your immune system overreacts to a harmless substance, like pollen, dust, or animal dander.  Cells in your airway release substances like histamine, making you sneeze.  It also causes the mucous membranes in the nose to swell and the glands to produce more mucus. 
There are two general types of secretions in the nose:  allergies, eating spicy food, and being outside in the cold can result in a watery nasal leakage and a thicker mucus when you have a cold (caused by viruses) or sinus infection (caused by bacteria). 
Most mucus problems are temporary.  However, producing too much mucus contributes to some severe conditions, including cystic fibrosis, a genetic disorder that causes mucus in the lungs to become thick and glue-like.
 
Colors of Mucus
Mucus can come in a range of colors.  Although usually clear, you may find it cloudy or yellowish during a cold.  Proteins released by the cells that cause inflammation can get stuck in the mucus and give it this color.  Brown or black mucus is common in heavy smokers and some lung diseases. Greenish, brownish, or bloody colors may signal a bacterial infection.
But this is not always the case.  Determining what is wrong simply by your mucus color can be challenging since many things can cause your body to make too much mucus.  Doctors rely on other clues to diagnose and treat the problem.