Mucus is produced along the entire course of the respiratory tract, from the nose to the lungs. It serves several important functions, such as keeping the respiratory tract moist which is prone to drying with airflow and to trap dust and microbes which may enter with the inflowing air. However, there are instances where mucus production becomes excessive and even stuck in one part of the respiratory tract.
Source of Mucus in the Throat
The throat (pharynx) is lined with largely the same mucous membrane as the rest of the respiratory tract. It produces its own mucus in moderate quantities to both keep the throat moist and trap dust or other foreign particles, including microbes. However, mucus in the throat may also be due to other sources.
- Nasal mucus since the throat (pharynx) and nasal cavity meet at the nasopharynx. Mucus from the paranasal sinuses may also empty into the nasal cavity and reach the throat.
- Oral mucus since the throat and mouth cavity meet at the oropharynx.
- Lower respiratory tract mucus from the larynx, trachea, bronchi and even lungs which may be coughed up into the throat.
- Gastrointestinal mucus from the esophagus which continues from the throat and even stomach mucus can be carried up as high as the throat.
Read more on coughing up mucus.
Causes of Throat Mucus
Mucus in the throat has been discussed according to the different causes of excessive mucus production from the neighboring parts of the digestive and respiratory tracts. Apart from injury, infections and allergies, cancers in certain areas of these tracts may also cause excessive mucus production.
Excessive throat mucus is produced when the mucous membrane lining the throat becomes inflamed (pharyngitis or commonly referred to as a sore throat). This can occur for several different reasons, such as throat infections, irritation or injury, as well as with allergic reactions.
- Infections caused by viruses or bacteria, such as the common cold or a strep throat respectively.
- Injury caused by mechanical or chemical irritation as may occur with inhalation of toxic gases, fumes or acid that rises up from the stomach.
- Allergies triggered by ingested allergens (certain foods) and inhaled allergens (like mold, pollen, animal hair/fur).
Other throat inflammation symptoms may include a shallow cough, sore throat (discomfort or pain), hoarse voice, difficulty or painful swallowing and bad breath. However, it is not uncommon for the excessive mucus in the throat to originate in the neighboring parts of the respiratory and gastrointestinal tract.
Larynx and Respiratory Tract
As with the throat, excessive mucus emanating from the larynx and lower respiratory tract may occur for the same reasons such as injury, irritation, infection and allergies. Some of the conditions which may cause mucus from these areas include:
- Asthma is a condition where the airways narrow due to constriction of the bronchi, swelling of the lower airways and mucus build up. It is often related to allergies.
- Laryngitis is inflammation of the larynx, which lies between the throat and trachea. It is often due to infection but may also arise with injury and allergies. A common non-infectious cause is acid reflux.
- Bronchitis is inflammation of the bronchi, the two smaller tubes that lead to the lungs. Acute bronchitis mainly occurs due to viral and bacterial infections. Chronic bronchitis is a COPD that is often caused by long term tobacco smoking.
- Pneumonia is an infection of the lung that may be due to viruses, bacteria and sometimes fungi. Pneumonitis is a term used to describe non-infectious lung inflammation which may be due to mechanical or chemical injury and sometimes due to allergic reactions.
Other symptoms include coughing, difficulty breathing, hoarse voice, throat and/or chest pain and abnormal breathing sounds such as wheezing.
Nose and Paranasal Sinuses
Air that flows in through the nose passes through the nasal cavity to the throat. The paranasal sinuses connect to the nasal cavity. Inflammation of the lining of the nasal and paranasal sinus cavities may result in excessive mucus production which may then drain into the throat.
- Rhinitis and sinusitis tend to occur with viral infections such as the common cold or flu, as well as bacterial infections. Both cavities are simultaneously affected and jointly referred to as rhinosinusitis. Non-allergic rhinitis may also arise with mechanical and chemical irritants.
- Allergic rhinitis is a common condition where the nasal mucosa reacts to harmless substances (allergens) such as molds, pollen, dust and animal hair/fur among other substances.
- Post nasal drip is where excessive mucus collects in the throat and may be due to a host of different allergic or non-allergic conditions that cause excessive mucus production in the nasal cavity.
Other symptoms may include a runny nose, nasal congestion, sneezing, nasal tone of the voice, reduced sense of smell and a cough.
Hypersalivation is a term used to describe excessive saliva in the mouth. Saliva is a combination of mucus and serous fluids with digestive enzymes like ptyalin. It is produced by the salivary glands. Most saliva is swallowed where it passes down the throat, into the esophagus and then into the stomach.
Any condition that causes hypersalivation may also cause excessive mucus in the throat. It depends on the mucus and serous fluid mix of the produced saliva but since mucus tends to be more sticky, it is more likely to adhere to the back of the throat as it is being swallowed.
Read more on excessive saliva.
Upper Digestive Tract
Mucus in the throat may also arise from the esophagus or the stomach. Normally the esophagus produces moderate amounts of mucus which aids in the movement of food down to the stomach. The esophagus produces large amounts of mucus when irritated, injured or infected which may arise in esophagitis (inflammation of the esophagus). Stomach secretions should not enter the esophagus since the lower esophageal sphincter (LES) prevents backflow.
However, the LES can malfunction for several reasons which results in gastroesophageal reflux disease (GERD) which is also known as acid reflux. In fact acid reflux is one of the most common causes of esophagitis as well. Therefore mucus from both the stomach and other gastric secretions as well as esophageal mucus may become lodged in the throat.
Laryngopharyngeal reflux (LPR) is where the acid reflux causes irritation and injury of the throat (pharynx) and larynx. This may in turn cause these areas to produce copious amounts of mucus. LPR is also referred to as silent reflux since the symptoms of an inflamed pharynx (reflux pharyngitis) and/or inflamed larynx (reflux laryngitis) may occur without the typical acid reflux symptoms like heartburn.
Read more on LPR reflux.