Normal Mucus in the Mouth
The mouth is moisturized and lubricated mainly by the secretions of the major salivary glands although the minor salivary glands and mucus producing cells in the lining of the inside of the mouth also contribute towards it. Saliva is a combination of a mucus and serous secretion. Mucus is thicker while the serous component is thinner.
The secretion of the mucoid component of fluid occurs throughout the day while the serous portion, containing the digestive enzyme ptyalin, is mainly released wheng eating. Throughout the day, the glands are secreting some 0.5 milliliters of saliva per minute – sometimes more, sometimes less. This can increase to about twenty-fold when eating or if saliva secretion is triggered by some other factor.
Reasons for Mucus in the Mouth
Mucus in the mouth usually arises from three sites :
- Salivary and buccal glands of the mouth
- Mucus from the nose and paranasal sinuses
- Mucus from the airways including the throat, larynx and trachea
Most of the time the mucus from the nasal cavity and and airways empty into the esophagus and pass down the gut. This mucus contains dust and microbes trapped in the nasal cavity and airways. However, it is also possible to cough up the mucus or allow it to drain through the nose. When the nasal lining is irritated, excess mucus is also sneezed out. Dried nasal mucus is usually removed at will.
The walls of the esophagus (food pipe) are also laden with mucus glands to lubricate the passage of food during swallowing. Significant amounts of esophageal mucus do not usually empty into the mouth as easily since the swallowing reflex pushes it down towards the stomach. Similarly it is unlikely for mucus from lower down the gut to enter into the mouth except momentarily during vomiting or with reflux.
What does mucus in the mouth mean?
Mucus in the mouth is not necessarily a cause for concern. It is only when the mucus is excessive, persistent, tinged with blood (read more on mucus colors), has an offensive smell and impairs taste or swallowing that it needs to be investigated. Mucus in the mouth is more of an inconvenience in most instances particularly when it is thick and sticky.
Simply drinking water usually washes out mucus. It is important to note that in the early stages of dehydration, the saliva in the mouth may be thicker than normal. Eventually saliva secretion reduces drastically and the mouth becomes dry as the dehydration worsens. Excessive saliva secretion with hunger, thirst and seeing or thinking of appetizing foods may also be factors although the saliva is not entirely mucoid.
Causes of Excessive Mucus in the Mouth
Excessive mucus in the mouth can originate from any of the sites mentioned above and sometimes even from the esophagus. Firstly the causes of excessive salivation should be taken into consideration as mucus is a component of saliva. However, a thicker more mucoid discharge is more likely when there is only mucus secretion. The causative conditions of excessive salivation may include :
- Oral and dentals problems such as :
- poorly fitting dentures, bridges and implants.
- bruxism – teeth grinding and jaw clenching.
- temporomandibular joint (TMJ) problems.
- Lifestyle factors :
- tobacco chewing
- mouth breathing
- certain foods and drinks, including sweets and soft drinks
- Mouth infections and inflammation :
- stomatitis – infections, injury (chemical or mechanical) and allergies
- mouth pain
- Nerve problems like :
- trigeminal neuralgia
- Bell’s palsy
- Certain medication :
- psychoactive drugs
- nicotine (excessive use)
Mucus from the Nose
Excessive mucus in the nasal cavity including from the paranasal sinuses may drain into the mouth. It is part of the airway but discussed separately since it is one of the main causes of excessive mucus in the mouth. This includes :
- Rhinitis (inflammation of the nose) :
- Infections, particularly viral and bacterial.
- Irritants, like dust, smoke, smog and strong odors
- Trauma, especially nose picking.
- Medication may also cause rhinitis or stimulate mucus production without the nasal lining being inflamed.
- Foreign body trapped in the nose may not only irritate the lining but also prevent mucus from escaping through the nose.
- Obstructions like a nasal polyp and deviated septum.
- Post-nasal drip.
- Sinusitis (inflammation of the paranasal sinuses)
Mucus from the Airways
Mucus from the airways may be coughed up into the mouth. It is usually swallowed or spat out immediately. Some of the causes of excess airway mucus includes :
- Acute bronchitis usually caused by infections.
- Cancer – lung, bronchus.
- Chronic bronchitis seen especially in long term smoking.
- Cystic fibrosis
- Occupational lung diseases like asbestosis and silicosis.
- Otitis media (middle ear) as mucus enters the back of the throat.
Mucus from the Esophagus
Mucus from the esophagus usually passes downwards into the stomach but any obstruction may cause it to be regurgitated into the mouth. Vomiting and reflux also allows mucus from the upper gut can pass into the mouth. Even without an obstruction, esophageal mucus can sometimes pass into the mouth when it is excessive or when the swallowing reflex is dulled either during deep sleep or with disease. Therefore the causes of mucus in the mouth originating from the esophagus includes :
- Esophageal strictures (narrowing of the esophagus)
- Foreign body in the esophagus
- Gastroesophageal reflux disease (GERD) / laryngopharyngeal reflux (LPR)
- Hypomobility of the esophagus