Saliva is the major fluid that lubricates and maintains the moisture in the mouth. Both major and minor salivary glands in the mouth secrete saliva continuously throughout the day. About 0.5mL of saliva is secreted by the various glands in the mouth every minute. The exact amount of saliva secretion can vary depending on a host a factors. The amount of saliva secreted can increase up to 20-fold from the baseline level when eating.
Reasons for Mucus in Saliva
Saliva contains both serous and mucus components. The serous component of saliva is thinner compared to the mucus component in the saliva. Apart from the major and minor salivary glands, other cells present in the lining of the mouth also secrete mucus. Whereas mucus is secreted continuously throughout the day, serous secretion occurs mostly while eating. The serous component of saliva contains the ptyalin enzyme, which plays a role in digestion.
Mucus is a normal component of the mouth. The amount of mucus present in the mouth at any given time can vary a lot. Food and other stimuli can affect the secretion of saliva and mucus. These changes in the amount of mucus in the mouth are normal, and rarely a cause for concern. However, some changes in the quantity and composition of mucus may indicate an abnormality. Some of the abnormal changes in mucus in the mouth include:
- Abnormally excessive production of mucus.
- Dry mouth caused by very low production of mucus.
- Presence of blood in the mucus.
- Offensive smell in the mucus.
- Abnormal taste of mucus.
In most cases, drinking water can help in getting rid of the excess mucus in the mouth. Abnormally thick saliva can occur during the early stages of dehydration. As saliva production decreases, the mouth may eventually become dry.
Sources of Mucus in the Mouth
The majority of mucus production in the mouth occurs in the salivary glands. However, other glands and cells that line the oral and respiratory passages also contribute to the mucus in the mouth. The following three sites are mainly responsible for the mucus present in the mouth:
- Salivary glands and buccal glands present in the oral cavity.
- Mucus producing cells in the nasal passages and paranasal sinuses.
- Mucus producing cells in the throat, larynx and trachea.
The mucus in the nasal and upper respiratory passages typically contains microbes and dust that get trapped during respiration. The mucus produced from the nasal and upper respiratory passages usually drains into the esophagus and enters the gut. The mucus from the nasal and upper respiratory passages could also be expelled via the nasal or oral cavity during sneezing or coughing. Mucus that dries up in the nasal passages is typically removed manually and voluntarily.
Swallowing of food is made easier by the mucus that is present in the oral cavity and the esophagus. Mucus-producing glands are also present in the esophagus. The mucus produced by these glands in the esophagus usually drain down the gut. Mucus produced by glands situated in the lower part of the gut also drain down the gut. However, gastric reflux and vomiting may bring the mucus from these lower parts of the tract into the mouth.
Causes of Excessive Mucus in the Mouth
As described earlier, mucus production occurs in many different glands present in the oral cavity, nasal cavity, throat, esophagus, and respiratory passages. Therefore, the source of excessive mucus in the mouth could be any of these glands.
Since the majority of mucus in the mouth comes from saliva, one must first consider excessive salivation as the most likely cause of excessive mucus in the mouth. However, there is also the possibility that excessive mucus secretion is independent of the saliva production, especially when the mucus in the mouth is thicker than normal.
Read more on excessive salivation.
Excessive salivation or mucus in the mouth can be caused by oral and dental problems. Examples of such conditions include problems with temporomandibular joint, ill-fitting dentures, bruxism, and jaw clenching. Injuries, infections, and inflammation in the mouth can also cause excessive salivation and mucus production.
Excessive mucus in the mouth could also occur in case of nerve problems, such as Bell’s palsy and trigeminal neuralgia.
Drugs such as ketamines, nicotine, cholinergics and narcotics can also cause excessive salivation.
Certain lifestyle factors such as chewing tobacco, mouth breathing, and excessive consumption of soft drinks and sweets can also lead to excessive mucus in the mouth.
Excessive mucus from outside the mouth
Excessive mucus production in the nasal cavity and paranasal sinuses can also contribute to the mucus in the mouth. The following are some of the possible causes of excessive mucus production in the nasal passages:
- Inflammation: Inflammation of the nasal passages and sinuses can lead to excessive mucus production in the nose. Inflammation in these regions can occur due to conditions such as rhinitis, sinusitis, bacterial infections, trauma, and inhalation of volatile irritants.
- Medication: Mucus production in the nose may also get stimulated by certain medications. Certain medications may also contribute to rhinitis.
- Foreign body: The lining of the nose can get irritated due to the lodging of a foreign body in the nasal passages. The trapped foreign body may also prevent expulsion of mucus through the nose.
- Nasal obstructions: Nasal obstructions caused by a deviated nasal septum or the presence of nasal polyps could also contribute to excessive mucus in the nose.
Excessive mucus in the mouth may also come from the respiratory airways. Coughing and sneezing can bring the mucus from the airways into the mouth. Potential causes of excessive mucus production in the airways include:
- Cystic fibrosis
- Occupational lung diseases (such as silicosis and asbestosis)
- Lung cancer
- Otitis media
Mucus present in the esophagus passes down the gut under normal conditions. However, this mucus may also be regurgitated into the mouth under the following conditions:
- Esophageal obstruction or stricture.
- Inflammation of the esophagus.
- Gastric reflux, gastroesophageal reflux disease, and laryngopharyngeal reflux.
- Presence of foreign body in the esophagus.
- Dulled swallowing reflex or esophageal hypomobility.