Taste sensations can sometimes persist long after eating or drinking. These persistent taste sensations are mainly caused by remnants of food that get stuck in the mouth. Food particles can get stuck in various parts of the mouth such as on or under the tongue, in between teeth, on the palate, and in various crevices within the oral cavity. Upon coming in contact with saliva, these remnant food particles in the oral cavity can trigger taste sensations by activating the taste buds.
Not all foods get stuck in the mouth during the chewing and swallowing processes. Some foods are more likely than others to get stuck in various parts of the oral cavity (such as the tongue and the spaces between the teeth). Bitter taste sensations can be caused by foods such as dark chocolates, vegetables like bitter gourd, pickles, and pine nuts. These tastes can persist if there is insufficient fluid intake to flush out the bitter-tasting chemicals.
In some cases, a persistent bitter sensation in the mouth may have nothing to do with ingestion of bitter foods. The source of bitter sensation in these cases may be stomach acid that gets regurgitated into the throat and the mouth. Stomach acid reflux is especially more likely to occur after a spicy and oily meal. There may also non-gastrointestinal reasons for an abnormal bitter taste sensation in the mouth.
Technically, an abnormal taste sensation in the mouth is referred to as dysgeusia or parageusia. If the taste sensation is bad, then the condition is known as cacogeusia. Both dysgeusia and cacogeusia could occur due to many different causes, which may not be related to food intake at all.
Read more on bad taste in the mouth.
Causes of Abnormal Bitter Tastes
The possible causes of abnormal bitter taste in the mouth may be categorized into two types: gastrointestinal and non-gastrointestinal. The following are some of the possible gastrointestinal causes of bitter taste sensation in the mouth.
Acute acid reflux
Acid secretion in the stomach mainly occurs in response to food. However, gastric acid secretion can occur even before the food reaches the stomach. The secretion of acid in the stomach can be stimulated by thoughts, smells, sights, and taste of foods. This phase of acid secretion in the stomach is referred to as the cephalic phase of gastric acid secretion.
Entry of food into the stomach increases gastric acid secretion substantially. As long as the food is in the stomach, gastric acid secretion continues. This continuous production of gastric acid is under the control of nervous stimuli from the brain (vasovagal) and the intestine (enteric plexus). This phase is referred to as the gastric phase of stomach acid secretion. As the food passes out of the stomach and into the duodenum, the secretion of stomach acid reduces.
However, gastric acid secretion does not cease at this stage. The gastrin hormone released from the duodenum (in response to food inflow) stimulates the stomach to continue producing gastric acid, albeit at lower levels than in the gastric phase. This phase of stomach acid secretion is known as the intestinal phase of gastric acid secretion. Due to these three stages of gastric acid secretion, acid may persist in the stomach even before or after the passage of food through the stomach.
A reflux of the stomach acid into the esophagus can trigger a sour or bitter taste sensation in the mouth. Under normal circumstances, the backward flow of acid from the stomach into the esophagus is prevented by the action of the lower esophageal sphincter (abbreviated as LES). However, the lower esophageal sphincter may fail to prevent acid reflux under certain conditions such as alcohol consumption, eating large meals, lying down after a large meal, exercising immediately after a meal, and excessive abdominal pressure (frequently caused by tight clothes). Acid reflux is a temporary condition.
Some common symptoms of acid reflux include nausea, water brash, indigestion and heartburn. In some cases, acid reflux may elicit just a sore throat and an unusual sour or bitter taste in the mouth. Such cases are referred to as silent acid reflux. The bitter taste in acid reflux may also be caused by an accompanying bile reflux. Bile is very bitter in taste.
Gastroesophageal reflux disease (commonly abbreviated as GERD) is the medical term for acid reflux. The main cause is improper functioning of the lower esophageal sphincter. Other factors, such as hiatal hernia, delayed gastric emptying, and an increase in the intra-abdominal pressure due to obesity or pregnancy, may also contribute to the condition.
A characteristic symptom of gastroesophageal reflux disease is the occurrence of sore throat and sour taste sensation in the mornings after getting up. Lying down immediately after eating exacerbates the symptoms of gastroesophageal reflux disease. Bitter taste sensation in the mouth due to non-gastrointestinal causes is relatively less common. The bitter taste in these cases is mostly caused by the presence of blood, pus, or mucus in the mouth.
Read more on GERD.
- Tooth cavity: Cavities in teeth are very common and are mainly caused by excessive consumption of sugary drinks, poor dental hygiene, and bacterial infections. Left untreated, tooth cavities may lead to pus formation and bleeding that can cause bitter taste sensations in the mouth.
- Sores in the mouth: Ulcers and sores in the mouth can result from a variety of factors. Tissue injury and infections of these lesions can result in a bitter taste in the mouth.
- Allergic respiratory conditions: Allergic conditions of the respiratory tract, such as asthma and allergic rhinitis, are characterized by increased mucus secretions in the nasal cavity and the respiratory passages. These conditions can also lead to a bitter taste in the mouth.
- Acute sinusitis: Inflammation of sinuses that lie in close proximity to the oral cavity can also result in an abnormal bitter taste in the mouth.
- Tonsillitis: Inflammation of the tonsils that lie at the back of the throat may be accompanied by bitter taste in the mouth.
- Infections of the salivary gland: Bitter taste in the mouth can also be caused by infections of the salivary glands. An example of such an infection is bacterial parotitis.
- Neurological conditions: Abnormal taste sensations (paresthesia) can be caused by certain neurological disorders. This is especially the case with neurological problems that involve the facial nerve (also referred to as the 7th cranial nerve).
- Abscess: The presence of abscess (pus) in the oral cavity, sinuses, throat and upper respiratory passages can lead to an abnormal bitter taste in the mouth.
- Metabolic conditions: Abnormal taste in the mouth is also observed in certain metabolic conditions such as diabetes mellitus. This disease is characterized by an increase in blood glucose level and fat breakdown.