What Is Mucus? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Mucus — less elegantly known as snot — may be annoying when you're sick, or when it feels like you have too much of it, but your body needs it to stay healthy.

Technically, mucus is a sticky, gelatinous material that lines your lungs, throat, mouth, nose, and sinuses.

It's produced by membranes in the nose and sinuses, and its main function is to trap bacteria, viruses, and allergens like dust or pollen in your nose and prevent them from spreading through your body and making you sick. Eventually, the mucus, and the substances it has trapped, will head to the stomach and pass out of the body. (1)

Mucus is also made by the digestive system, the cervix, and the urinary tract. But we’ll be focusing here on respiratory mucus.

Mucus production serves many purposes, even when you're healthy. It protects the tissue that lines your lungs, throat, and nasal and sinus passages and keeps them from drying out. Mucus contains antibodies and enzymes, designed to kill or neutralize harmful bacteria in the air. Think of it as a line of defense that can prevent you from getting sick.

If everything is working as it should, you won’t even notice your mucus. But if you have an infection, it may change color. If you smoke or are exposed to an irritant in the air, you may produce more of it than usual. If you start producing too much clear mucus, it might mean you’re experiencing allergies and your body is trying to get rid of irritants like pollen or dust. (2)

With a cold, a sinus infection, or bronchitis, your mucus may turn light yellow, beige, or greenish. The reason? When you have an infection, your body produces more white blood cells, and sends them to your airways to fight it. Those white blood cells contain a substance called neutrophil, which can give your mucus a yellow or greenish color. Mucus may also appear to be green when it thickens.

Or you may notice a red or brown color in your mucus after you blow your nose. This is often a sign that there's blood in your mucus, which is generally the result of irritation and the drying out of tissue lining the nasal passages, caused by excessive rubbing, wiping, or blowing your nose.

A little bit of blood in your mucus is nothing to worry about. But if you experience excessive bleeding, talk to your doctor. This may be a sign of a serious infection, such as bronchitis, pneumonia, or cancer.

Phlegm, a type of mucus, is produced by the lungs and respiratory system. It’s a sign of inflammation and irritation. (Mucus is produced by the nose.) You might hear the term sputum used — this is phlegm that you expel through coughing.

If excess mucus is your only symptom, it’s not typically something to worry about. (3)

When you're sick, your body doesn't always produce more mucus, although it may feel like it. What you’re noticing is most likely a change in its consistency. Your mucus may become thicker or stickier. It may build up in your lungs and throat, causing congestion and — in severe cases — difficulty breathing or swallowing.

You may experience postnasal drip as a result of this buildup. This occurs when excess mucus at the back of the nose drips down the throat. It often leads to a cough.

Thick mucus can also be a sign that your mucous membranes are too dry, perhaps as a result of the following:

• A dry indoor environment (due to heat or air-conditioning)
• Not drinking enough water or other fluids
• Drinking beverages such as coffee, tea, or alcohol, which can lead to dehydration
• Taking certain medications
• Smoking

Excessive mucus can be a symptom of bronchitis, chronic obstructive pulmonary disease (COPD), bronchiectasis, or cystic fibrosis. See more on those conditions below.

If you think you might have allergies, a cold, or a respiratory infection, or notice a change in your mucus that concerns you, talk to your healthcare provider, who will assess the quantity, consistency, and color of your mucus when making a diagnosis.

Prognosis of Abnormal Mucus

While most mucus problems are short-term, too much mucus can be a sign of a serious condition, most notably cystic fibrosis. This is a genetic condition that usually develops in the first few years of life; it can also appear in young adulthood.

RELATED: Taking Control of Your Life With Cystic Fibrosis

Excess mucus can be treated with medications or with home remedies.

Medication Options

Decongestants You can use an over-the-counter (OTC) nasal or oral decongestant to reduce the amount of mucus in your lungs or nasal passages. These medications clear up thick mucus, but shouldn't be overused, since they can lead to side effects or complications.

Decongestants work by narrowing the blood vessels in your nasal passages, restricting blood flow, and reducing the amount of mucus produced. The trouble is, if overused, these drugs can actually dry up your mucous membranes and thicken the mucus they produce, which leads to congestion. Decongestants have also been linked to side effects such as dizziness, nervousness, and high blood pressure.

Antihistamines These medications are designed to block or limit the activity of histamine, a substance your body produces during an allergic reaction. They’re great for treating symptoms such as an itchy or runny nose, but can cause side effects including drowsiness, dizziness, dry mouth, and headache — especially if they're overused.

Expectorants Cold and flu medications, both OTC and prescription, contain expectorants (for example, guaifenesin), which make mucus thinner and easier for your body to get rid of.

Alternative and Complementary Therapies for Excess Mucus

Nasal irrigation is a natural method for getting rid of excess mucus. It can be performed using a neti pot, a bulb syringe, or a squeeze bottle containing salt water. By pumping salt water into your nostrils, you can help loosen up the mucus in your nasal passages and flush it out.

One important caveat: The U.S. Food and Drug Administration (FDA) says to use only distilled, sterile, or boiled water. Tap water should not be used because it’s not adequately filtered or treated. (4) Tap water can contain low levels of microorganisms that, when swallowed, are usually killed by stomach acid. In your nasal passages, however, these bugs can stick around and cause potentially serious infections. In very rare cases, says the Centers for Disease Control and Prevention (CDC), they can be fatal. (5)

As with decongestants and antihistamines, overuse of nasal irrigation can lead to complications.

Although the flushing process does help thin out mucus and remove bacteria and allergens, it can also wash away some of the mucous membrane and other protective tissue that keeps you from getting sick.

To reduce mucus and congestion, the Cleveland Clinic recommends doing the following: (3)

• Drink more water (enough so that your urine is pale) and go easy on beverages loaded with caffeine, which can be dehydrating.
• Try a humidifier to keep your throat and nasal passages moist (this counteracts excessive mucus and phlegm production).
• Make sure filters on your heating and cooling system are clean; this can help reduce airborne irritants.
• Try a saline nasal spray, which helps keep nasal tissues and sinuses moist.

It may also help to give yourself a dose of heat and steam. Try breathing through a warm washcloth, or turning on the shower and inhaling the steam, which can make your mucus thinner and easier to clear.

Prevention of Mucus

You don’t want to prevent mucus from forming in your body. But you can try the strategies and medications suggested above if you want to prevent excess mucus or address thick mucus.

If mucus is not cleared, it can create conditions for infection and inflammation. (6)

Your body makes a lot of mucus — about 1.5 liters every day. That’s a good thing; a review published in February 2016 in Cell Host & Microbe suggests that mucus can provide an important barrier against the influenza virus. (7)

Excess mucus may be a symptom of chronic obstructive pulmonary disease (COPD). There are two main types of COPD — emphysema and chronic bronchitis — and many people with this condition have both. (8) It may also be a sign of a condition called bronchiectasis, in which the tubes in your lungs become inflamed and lose their ability to effectively clear out mucus.

Very thick mucus can be a sign of cystic fibrosis, a genetic disorder that affects the cells that produce mucus and other substances. With cystic fibrosis, mucus can grow thick enough to clog your lungs and block your digestive system. (9)

Favorite Organizations 

American Lung Association

Originally founded to fight tuberculosis, this nonprofit organization has been a trusted source of information on lung health and conditions that affect the lungs since 1904.

National Heart, Lung, and Blood Institute

Visit this government site for more information on COPD and other respiratory conditions.

Cystic Fibrosis Foundation

Founded in 1955, this organization funds research into the condition, and its website has a wealth of information for those living with or taking care of someone with cystic fibrosis.