Bitter Taste In The Mouth

Taste disorders are common, with an estimated 19% of adults in the United States suffering from taste disturbances.¹ Dysgeusia is a condition that is characterised by taste alteration where everything seems bitter, metallic, and sour.² Having a persistent bitter taste is an annoying and irritating feeling, but more importantly, this chronic alteration in taste sensing may be a signof underlying health conditions. 

Why do I have a bitter taste in my mouth?

It is expected to have a bitter taste in your mouth if you consume bitter or sour food. Yet, it is not normal to have a persistent bitter taste if you don’t eat or drink anything. Taste is a complex sensation that involves 2000 to 8000 taste buds in the mouth. Each taste bud contains up to 50 taste receptors. These receptors are responsible for taste sensation and detection of food, allowing you to differentiate whether the food is salty, bitter, umami, sweet or sour. Taste buds then transfer information to the brain through several nerve pathways³ 

Taste disorders occur as a result of receptor variation, reduction in the number of viable taste buds, nerve damage and reduction in salivary flow that plays an essential role in tasting food, making the receptors more sensitive to bitter taste. 

Signs and symptoms of bitter taste⁶

• All food tastes metallic and bitter
• Abitter taste persists in the mouth even without eating or drinking anything
• Good food tastes bad and even rotten 

Causes of bitter taste

Several health conditions may be the cause of a bitter taste in the mouth, affecting the patient’s quality of life and daily diet. Hence, it is important to know the underlying cause behind chronic bitter taste to treat it properly:   

• Infection⁴ 

When you are dealing with an infection, such as a cold or a sinus infection, the body releases proteins to mediate and reduce inflammation. These anti-inflammatory proteins affect taste buds by increasing the taste buds’ sensitivity to bitter taste for the duration of an illness.

• COVID and taste alteration⁷

During the COVID pandemic, one of the symptoms observed was taste alteration. Taste disturbances occur due to viral-induced damage to taste buds, nerves involved in taste sensation or brain areas responsible for taste sensory processing.

• Oral thrush¹⁰

Oral thrush is a yeast infection in the mouth where white spots appear on the tongue, mouth or throat. It causes a bitter taste in the mouth that persists if the infection is not treated.

• Dental issues^4,5

Poor oral hygiene is considered to be a reason for experiencing a bitter taste in the mouth, Mmoreover, as it increasesing the risk of developming dental problems like caries, gum disease and infections. 

• Burning mouth syndrome⁸

Burning mouth syndrome is characteriszed by a painful burning and scalding sensation in the mouth. and experiencing bA bitter and metallic taste, that may be chronic and stays for a long timelong-term, can also occur.

The cause of burning mouth syndrome is unknown but it is linked to underlying causes such is associated with as cancer treatments, diabetes mellitus andor hormonal disturbances during menopause.  

• Dry mouth¹⁰

Dry mouth, also named known as xerostomia, occurs due to decreased salivary flow. The causes of salivary reduction may be:

• Ageing
• Smoking
• Autoimmune diseases
• Medication

Xerostomia causes taste alteration which induces as a feeling of a bitter taste in the mouth., Iin addition, it can also causeto gum diseases, caries tooth decay and difficulty swallowing.

• Pregnancy⁴

Sex hormones (estrogen and progesterone) that fluctuate during pregnancy cause taste bud alteration, resulting in a  metallicor bitter taste sensation during pregnancy, especially in the first trimester. This resolves after giving birth.

• Menopause⁶

Changes in estrogen hormone levels occur during menopause., where lLower levels of estrogen cause burning mouth syndrome and a bitter taste in the mouth.

• Gastroesophageal reflux disease (GERD)⁴

GERD, or acid reflux, is considered the most common cause of bitter taste in the mouth. GERD is caused by the weakening of the muscles at the top of the stomach which allows food and stomach acid to move back from the stomach to the esophagus and the mouth. Symptoms of GERD includes a bitter and sour taste in the mouth, difficulty swallowing, a chronic dry cough and a burning sensation in the chest after meals.

• Pine nut syndrome⁹

Pine nut syndrome is a temporary syndrome, characterised by a metallic and bitter taste in the mouth that occurs after eating pine nuts.

• Medications^4,5

Certain medications can cause taste disorders. This can happen due to the bitter taste of the medication itself, the presence of chemicals in the medication that are released into the saliva or through the activation specific taste receptors responsible for detecting bitter, sour or metallic tastes. Medications that can cause a bitter taste in the mouth includes:

• Antibiotics, such as clarithromycin, tetracycline and metronidazole
• Lithium, which is a medication used to treat psychiatric disorders
• Antidepressant drugs
• Some cardiac medications, such as captopril
• Oral supplements and vitamins that contain high amounts of metallic substances, such as zinc, iron, copper, and chromium
• Antiviral medication: paxlovid, used for COVID treatment, is effective in reducing the severity of COVID and decreasing COVID hospitalisations and deaths. But a side effect of paxlovid is dysgeusia.This is known as "paxlovid mouth"
• Anxiety¹¹

Stress and anxiety leads toan enhanced stress response in the body, causing mouth dryness and a bitter taste in the mouth.

• Age¹²

Nerve function is affected by age and this affects taste recognition. 

• Cancer treatment⁵

Patients undergoing cancer treatment, including chemotherapy and radiation treatment, experience taste bud irritation which causes taste alteration and a bitter, unpleasant taste in their mouth. 

• Smoking⁶

Tobacco smoking is a cause of bitter taste. 

• Neurological conditions¹²

Conditions such as dementia, multiple sclerosis, head trauma and depression affect a person's taste because taste buds send signals to the brain. Hence, damage to specific regions of the brain can causes taste alteration.

• Liver disease⁴

A diseased liver that is not working properly accumulates large amounts of ammonia, which is a toxic substance that is normally transferred into urea and excreted in the urine in case of a healthy liver. Increased levels of ammonia can cause dysgeusia changes in taste.

• Kidney failure¹³ 

End stage of kidney disease causes a metallic taste in the mouth.his is due to lower numbers of taste buds, changes in saliva flow and composition, medications, lower zinc levels and high levels of urea. 

• Autoimmune diseases¹⁴

Diseases such as Sjogren’s syndrome and sicca syndrome cause dryness in the mouth, sinuses and eyes. People suffering from these syndromes complain of metallic and bitter tastes in their mouth.

Treatment and home remedies

Treatment¹⁰

Bitter taste is treated by detecting and treating the underlying cause

• If infection is the cause, antibiotics will be prescribed
• If GERD is the cause, healthcare providers may prescribe antacids, H2 blockers and proton-pump inhibitors 
• Poor oral hygiene is enhanced by scaling, removal of dental plaque and proper oral hygiene 
• If hormones are the problem, hormonal therapy may be recommended 
• Medications that cause a bitter taste may be changed by healthcare providers 

Home remedies

Home remedies seek to reduce bitter taste but it doesn't treat the underlying health condition which causes dysgeusia. A visit to the doctor is required for a permanent solution. 

• Proper dental care which includes using a dental brush twice daily for 2 minutes, dental floss and use of anti-bacterial mouthwash⁴
• Drinking plenty of fluid and water daily⁴
• Avoiding spicy and greasy foods that increases the risk of acid reflux
• Stop tobacco smoking and alcohol drinking
• Chewing sugar-free gum to stimulate salivary flow in the mouth

When to seek medical attention

Seek medical treatment if: 

• Bitter taste persists
• No obvious cause for taste change 
• There are other signs and symptoms

Summary

Although dysgeusia is not considered a serious condition, it is an annoying one characterised by a persistent bitter taste in the mouth and taste alteration. It is caused by several conditions related to infections, oral health, medication side effects, metabolic conditions, hormonal changes and burning mouth syndrome. Proper diagnosis of the cause of bitter taste in the mouth is the key towards receiving proper treatment.