Mucus. It’s hard to even say the word without curling a lip in disgust. But this much-maligned secretion is really a superhero in disguise—a stoic defender of the unprotected parts of your body. Sound like too much horn-blowing for such a yucky substance? Not so.

Few people understand the important role that mucus plays in keeping us healthy…and how to keep one’s supply of this gooey substance functioning optimally. What you need to know…

WHAT MUCUS DOES

Mucus is a watery, slick secretion that forms a physical and chemical barrier on many of the body’s internal surfaces. Mucus protects the entire respiratory tract—that is, your nose, sinuses, mouth, throat, trachea, bronchial tubes and lungs—against foreign invaders such as bacteria and viruses. Mucus lubricates the surface and prevents excessive dryness.

The entire gastrointestinal tract, from mouth to colon to anus, as well as the genital tract in both males and females, produces mucus to perform these same functions. The principle of producing secretions like mucus is also present elsewhere in the body. For example, your eyes constantly produce a protective film of secretions that function just like mucus. We call them tears.

YOUR PROTECTOR

When your body senses danger, mucus is part of a defense system that kicks into gear. All mucus contains disease-fighting enzymes, chemicals and sometimes white blood cells called neutrophils. They work together to trap, inactivate or kill the foreign substances.

One purpose of mucus is to prevent these substances from entering the body. Having lots of mucus helps to wash away any offensive microorganisms and particles, such as bacteria and pollen. We blow our noses to eliminate mucus from our bodies. The remaining mucus is swallowed, digested and reabsorbed by the intestines. Stomach acid or enzymes from the pancreas should inactivate and destroy any disease-causing substances.

What you may not know: Any perceived attack—not only viruses, bacteria or allergens (such as pollen or pet dander) but also chemicals—can increase mucus production.

When this occurs, your mucus-making machinery can get busy when you least expect it. For example, the chemical compound capsaicin, which is found in chili peppers, will temporarily ramp up mucus production in the nose (making the nose “run”) in an effort to clear the irritant from the body.

And what about dairy products? Studies have not shown that dairy increases mucus production. When the question was investigated, researchers found only that milk causes phlegm (a sticky form of mucus) to thicken. However, in my practice, I’ve observed that mucus does increase in some patients—perhaps due to the individual’s reaction to the proteins in milk. My advice: If you feel that dairy increases your mucus production, you may be more comfortable if you cut back or eliminate your dairy intake.

A COLOR CHANGE

Healthy mucus is usually clear and thin. Sometimes, however, nasal mucus may change from clear to a deep yellow-green. This color change is due to the heavy presence of neutrophils. They are naturally light green in color, even though they’re considered “white” blood cells.

Anytime there is a greater concentration of neutrophils, secretions may appear green. This can happen, for instance, during a respiratory infection when extra neutrophils are dispatched to fight the infection…or if your mucus dries out due to dehydration.

What you may not know: Contrary to popular belief, greenish-yellow mucus does not always mean that you have a bacterial infection. You may have a viral infection. Yet many people make that faulty assumption and demand antibiotics from their doctors. Antibiotics, as most people know, do nothing to eliminate a viral infection.

A nasal or throat swab or sputum test can be performed to tell whether your infection is caused by bacteria (which may necessitate antibiotic treatment) or a virus (which you’ll have to live with until it passes).

DANGER SIGNS

In rare instances, mucus can signal a serious health problem.

What you may not know: If your nasal mucus turns brownish-black, it may be caused by a fungal infection (aspergillosis) of the lining of the nose. Aspergillus is a common mold found on dead leaves, rotting vegetation and in some heating and air-conditioning systems. When aspergillus particles are inhaled, an infection can develop in people with weakened immunity or lung disease. The infection also causes shortness of breath, fever and fatigue. Aspergillosis requires prompt treatment with steroids and antifungal medication or it can become fatal.

When your eye is the target of disease or irritation, mucus can alert you to a potential danger. With conjunctivitis (pink eye), the eye usually produces a watery discharge or white or light yellow mucus.

While most cases of pink eye are benign, some may progress and cause permanent damage to your vision. To prevent such damage, see a doctor promptly if you have green or yellow mucus coming from your eye or if you wake up with eyes sealed shut from dry, crusty mucus.

WHEN THE BODY AGES

As we get older, we lose our ability to control how much mucus we produce, leaving mucus-containing organs more prone to disease-causing organisms.

For example, decreased mucus production results in an increased risk for ear, nose, sinus, throat and lung infections, including pneumonia, because the body is less able to efficiently kill and clear away bacteria and viruses. To help maintain the full function of mucus-producing cells, it’s important to treat allergies and not smoke or snort products.

What you may not know: Mucus protects the sensors in the nose that are responsible for smell and taste. If the body does not make enough mucus to keep the inside of the nose moist, sensors in the nasal passages don’t function well and food tastes bland. One way to help retain these senses is with regular nasal washes (see below). Note: If the inside of your nose feels dry, it can also be a sign that you are dehydrated and need to drink more fluids.

A ONE-TWO PUNCH

Nasal irrigation may sound like a messy proposition, but it’s a healthy habit for most people. Irrigation can remoisten dry nasal passages if there’s not enough mucus…or it can help remove excess mucus when you have a bad cold or congested sinuses.

How nasal irrigation can help: If you have a runny nose with thick mucus, it’s a good idea to perform a nasal wash at least once a day. It helps remove excess mucus and whatever elements may be causing this excess, such as viruses, bacteria, allergens (such as pollen and molds) and irritant particles such as the chemicals in smoke. Also, don’t worry about leaving yourself “dried out”—the body simply produces more mucus.

A worthwhile daily habit: Even for those who are not battling an overabundance of mucus, a daily nasal wash can assist breathing and promote healthy nasal passages.*

You can use a bottled nasal irrigation product or saline solution. Such products include Ayr, Ocean, Simply Saline and drugstore brands. But this approach can become expensive with daily washes.

Many people prefer to use a teapot-shaped device called a neti pot. They’re available at drugstores and online for around $15. Follow label instructions.

To avoid infection, the FDA advises against using tap water, which may contain low levels of organisms such as bacteria and protozoa. Instead, the agency recommends using bottled distilled or sterile water…boiled and cooled tap water (boiled for three to five minutes, cooled to lukewarm and used within 24 hours)…or water passed through a filter designed to trap potentially infectious organisms.

Important: Make sure to wash your neti pot with hot water and soap after each use, rinse thoroughly and dry with a paper towel or let it air-dry to keep it free of mold, bacteria or other contaminants.

*If your immune system is compromised for any reason or if you’ve had recent nasal or sinus surgery or have a structural abnormality such as a deviated septum, consult your doctor before practicing nasal irrigation.