Causes and Risk Factors of Increased Mucus Production

There are many medical conditions and diseases that cause excessive mucus production. In some cases, the color and consistency of mucus you cough up can tell a lot about the underlying cause.

Too much mucus may be the result of a chronic respiratory condition like chronic obstructive pulmonary disease (COPD), an acute infection like bacterial pneumonia, or a lung disease like cystic fibrosis. While mucus can be beneficial to the body, producing too much mucus can cause breathing difficulties and an increased risk of secondary infection.

This article explains the causes of excess mucus in the lungs, and how genetics and lifestyle choices contribute to the problem.

Common Causes

Mucus (also called sputum) is produced by specialized cells called goblet cells that secrete mucus on the surface of mucous membranes, particularly those of the airways and lower digestive tract.

Mucus hypersecretion (overproduction) can occur when mucous membranes are exposed to infection, disease, inflammation, and irritants; this is the body's way of trying to protect the membranes from damage. In doing so, however, airways can become blocked and interfere with breathing, leading to coughing and shortness of breath.

People with chronic respiratory illnesses may have excessive mucus pretty much all the time. Others may only experience it during disease episodes or acute flare-ups (such as an asthma attack).

Conditions associated with excess mucus production include:

Respiratory Infection

Anyone can have a brief bout of a respiratory illness which can cause increased mucus in the lungs. In fact, acute respiratory tract infections are one of the most common reasons people seek medical care in the United States.

The common cold is a common trigger of upper respiratory tract infections. In severe cases, a respiratory infection can lead to bacterial pneumonia affecting the lower respiratory tract.

When you get a respiratory virus or bacteria, the lungs react by mounting an immune response. As part of the response, excess mucus is produced to prevent the foreign agent from invading lung tissues.

Other common upper and lower respiratory infections include:

• COVID-19
• Haemophilus influenzae type B
• Influenza (flu)
• Respiratory syncytial virus (RSV)
• Tuberculosis
• Whooping cough (pertussis)
  

Asthma

Asthma is characterized by episodes of respiratory distress that cause the narrowing of airways (bronchoconstriction) and respiratory spasms (bronchospasms).

During an asthma attack, you may also experience a severe hypersecretion of mucus, leading to airway obstruction. Approximately 20% to 40% of people with asthma experience this, often with mucus that is thicker and stickier than in people with COPD.

Chronic Bronchitis and Emphysema

Chronic bronchitis, a type of COPD, is associated with excess mucus production. The main cause is cigarette smoking. A diagnosis of chronic bronchitis is dependent on having a cough with active mucus production most days of the week for at least three months.

Another type of COPD, called emphysema, is also characterized by increased mucus production as well as a predisposition to recurrent lung infections. Emphysema is the more severe form of COPD, characterized by significant pitting in the lungs accompanied by often copious amounts of coughed-up mucus.

Allergy

Severe respiratory allergies can cause the rapid buildup of mucus in the lungs. One example is a form of asthma called allergic asthma in which an allergen (allergy-causing substance) like pollen, dust mites, and pet dander can trigger the excessive production of mucus and other symptoms.

A severe whole-body allergy called anaphylaxis can also cause the sudden hypersecretion of mucus, contributing to severe breathing problems and other life-threatening symptoms. Common causes of anaphylaxis include an allergy to insect stings, peanuts or tree nuts, foods like milk and shellfish, and certain medications (including antibiotics).

Bronchiectasis

Bronchiectasis is a condition characterized by the permanent widening of the airways, often accompanied by thick, foul-smelling mucus. Bronchiectasis is most often brought on by damage from another condition affecting the lungs, such as:

• Allergic bronchopulmonary aspergillosis (a fungal infection)
• Aspiration (the accidental inhalation of foreign objects into the lungs)
• Autoimmune diseases (like Sjögren's syndrome and rheumatoid arthritis that affect connective tissues)
• Cystic fibrosis
• Recurrent bacterial or fungal lung infections
• Severe childhood infections like whooping cough or measles

Pulmonary Edema

Pulmonary edema is a serious condition in which fluids accumulate in the lungs, leading to shortness of breath, wheezing, and trouble breathing when lying down. People with pulmonary edema often awaken soon after falling asleep, struggling for breath and describing feelings of drowning.

With pulmonary edema, the mucus is often frothy and may have a pink color due to the presence of blood.

Pulmonary edema may be due to a heart condition, like heart failure, that causes fluids to increase due to poor circulation (cardiogenic pulmonary edema). It may also be unrelated to the heart (noncardiogenic pulmonary edema) caused by things like:

• Acute kidney failure
• Acute respiratory distress syndrome (ARDS)
• Allergic reaction
• Aspiration
• Drowning
• Neurogenic pulmonary edema (caused by nervous system problems like a brain hemorrhage or epilepsy)

Genetic Disorders

There are several hereditary conditions associated with increased mucus. Some conditions directly affect the lungs while others impair the muscles involved in breathing, which leads to increased respiratory mucus:

• Cystic fibrosis (CF) is a genetic disease that affects multiple systems of the body, including the respiratory and digestive systems. Increased mucus is a primary characteristic of CF.
• Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterized by defective cilia (tiny, hair-like structures that move mucus and other substances through passages in the body). PCD leads to increased mucus in the lungs and a predisposition to lung infections.
• Neuromuscular conditions such as muscular dystrophy and spinal muscular atrophy can also lead to excess mucus because they impair muscle function. This, in turn, decreases lung movement when you inhale and exhale and reduces your strength and ability to cough. Then mucus pools in the lower lungs.

Lifestyle Risk Factors

Environmental irritants such as cigarette smoke and pollutants can cause the goblet cells to produce and secrete mucus while damaging the cilia and structures of the airways.

Exposure to these irritants, especially if you already have a lung disease, can substantially increase your risk of excess mucus in the lungs Common irritants include:

• Indoor air particles (dust or pet hair)
• Indoor or outdoor fumes or workplace emissions
• Outdoor air pollution
• Tobacco smoke

Summary

Anyone who has ever dealt with a respiratory infection like bronchitis knows that excess mucus comes with the territory. Other medical conditions that can trigger this state include asthma, pneumonia, and emphysema as well as genetic and environmental factors. When a healthcare provider identifies and treats the underlying cause, mucus production should return to normal.