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Achoo! What does your, ah, snot say about you?

You might be wearing the tell-tale colors of a cold: Your nose is dripping a clear liquid, and the skin near your nostrils is red from sniffling and sneezing. 

A doctor's exam may find the lining of your nose and throat is inflamed and red. And you could have white patches on your sore tonsils. 

But what about the gross gunk clogging up your nose, throat, and lungs? Can the shades of your secretions -- mucus and phlegm -- tell you anything about how long you'll be under the weather or what kind of bug you have? 

Dr. Stacey Tutt Gray is a sinus specialist at the Massachusetts Eye and Ear Infirmary in Boston, and she says it's not unusual for her patients to bring in their mucus-covered tissues to show her what's coming out of their bodies. So Gray is quite familiar with these secretions and her color-inspired last name makes her an ideal expert to explain their various hues. 

But first she points out that mucus is a liquid gel made up of mucin, a protein, and infection-fighting substances. It acts as a protective blanket over the lining of your nose, and the sticky substance can help trap and clear dust, allergens, bacteria, and viruses. 

You make roughly a quart of clear, thin mucus a day, which you usually just swallow. But snot production often cranks up, thickens, and discolors when you catch a cold, have allergies, or get an infection. 

Phlegm is also mucus that's coming from the chest and lungs. Technically, doctors call it sputum. Most people don't normally have phlegm, says Gray, but the lining of the airways has mucus in it to keep the lungs clear. 

A rainbow of mucus and phlegm
As far as color goes, mucus is typically clear. But when the immune system sends white blood cells into the nose to fight off infection, they contain a greenish enzyme that shades the substance yellow or green. These are the same tones mucus takes on when it dries and clumps into boogers.  

Red- or brown-tinged snot could occur when tiny blood vessels in your nose break from frequently blowing it. Black mucus can come from the noses of smokers or people who work in coal mines or dusty environments.

The phlegm palette is similarly multicolored to mucus with clear or white sputum being normal, yellow or green hues from frequent coughing, and red or brown shades from blood that's new or old. If you're seeing a lot of blood in phlegm, give your doctor a call. 

To thin down mucus or loosen phlegm, drink plenty of hot or cold liquids, and take a hot shower or inhale steam. Nasal rinsing with warm water can also help flush out congestion to make breathing easier. 

Gray says she is often asked by her patients with sinus trouble whether the color of mucus means a person has a bacterial infection and if they need an antibiotic. "The color in and of itself doesn't necessarily mean anything," she explains.

 A physician will determine whether an illness is viral or bacterial, an allergy or a sinus problem based on what a patient is saying about their other symptoms -- fever, body aches, nasal congestion, how long they've felt this way -- not just the color of mucus.  

So if you have a cold, you might see a rainbow of gook from your nose and chest. But it doesn't tell you much and it's usually nothing to worry about.

Related:

• Symptom tracker: Cold? Flu? Or something else?

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