Causes of a Sour or Bitter Taste in the Mouth

Having a bitter, sour, or foul taste in your mouth may be a simple reaction to something you ate. It's not uncommon to suddenly "burp up" something that didn't agree with you. However, the condition can be worrisome if it persists or recurs frequently. Three of the more common causes of a bad taste in the mouth are:

• Gastroesophageal reflux disease (GERD)
• Medications, including chemotherapy
• Zinc deficiency

Any distortion in the normal taste perception is referred to as dysgeusia. It is one of several conditions that affect the taste sensation, the others of which include hypogeusia (the loss of taste sensitivity) and ageusia (the complete lack of taste).

Diagnosing dysgeusia can sometimes be difficult, requiring the systematic exclusion of all other causes. Similarly, finding the right treatment can be a process of trial and error. In some cases, the dysgeusia may resolve on its own or require medical intervention to either control or resolve the underlying cause.

According to research published in the journal Canadian Family Physician, there are no less than 250 different drugs that can cause dysgeusia. This may be due to the impact a drug has on the taste receptors in the brain or simply caused by residual medications in the saliva.

It might also involve intravascular taste, a phenomenon by which a drug molecule circulating in a blood vessel of the tongue will interact with taste bud receptors.

Some of the more common drug culprits include:

• Antibiotics, including ampicillin, macrolides, quinolones, sulfamethoxazole, trimethoprim, tetracycline, and metronidazole
• Cardiac medications, including many high blood pressure medications, diuretics, statins, and antiarrhythmics
• Chemotherapy drugs, including cisplatin, cyclophosphamide, and etoposide
• Neurologic medications, including antiparkinson drugs, migraine medications, and muscle relaxants
• Psychotropic drugs, including most tricyclic antidepressants, some antipsychotics, anti-anxiety drugs, mood stabilizers, and hypnotics
• Other prescription and over-the-counter drugs, including thyroid drugs, antihistamines, bronchodilators, anti-inflammatories, smoking cessation aids, antifungals, and antivirals

While anyone can experience drug-induced dysgeusia, it is most common in the elderly, people undergoing chemotherapy, and those who take many multiple chronic medications (referred to as polypharmacy).

Diagnosis and Treatment

Drug-induced dysgeusia is typically diagnosed by exclusion. Doctors will often start by checking for infection, malignancy, nutritional deficiencies, or a reflux disorder. Based on the timing of the symptoms, the doctor may be able to pinpoint the problematic drug from those you are taking.

Drug-induced dysgeusia will usually trigger taste sensations described as metallic, bitter, foul, or rancid. By contrast, people undergoing chemotherapy will often experience sour, salty, or sweet sensations.

If appropriate, the offending drug may be stopped or substituted. In some cases, a dose may be taken at night instead of day to help minimize symptoms. If the dysgeusia is related to a short-term therapy, such as a course of antibiotics, you may need to bear with the unpleasant tastes until treatment is completed. Never stop taking a medication before speaking with your doctor.

Zinc deficiency is one of the more common causes of taste disturbances. While the exact cause is unknown, we do know that zinc increases the concentration of a protein known as gustin, which the body uses to produce taste buds. The taste disturbances associated with zinc deficiency are often difficult to describe, with some using terms such as "strange," "off," or simply "bad."

A zinc deficiency may be related to the lack of zinc in a diet, the poor absorption of zinc in the intestines, or the use of certain chronic medications. Malnutrition is also a common cause.

Among some of the diseases associated with zinc deficiency are cancer, celiac disease, chronic kidney disease, Crohn's disease, diabetes, liver disease, pancreatitis, sickle cell disease, and ulcerative colitis.

Alcohol, chemotherapy, thiazide diuretics, captopril (an ACE inhibitor), and penicillamine (used to treat kidney stones) are among the substances that can cause a zinc deficiency.

Diagnosis and Treatment

A zinc deficiency can be diagnosed by measuring the concentration of zinc in a sample of blood. Identifying the underlying cause is often a process of trial and error based on your age, weight, medical history, health status, current drug use, and co-occurring symptoms.

While a daily zinc supplement may help normalize blood levels, it can only provide relief if the underlying cause is treated or the offending drug is stopped, substituted, or dose-adjusted. Foods high in zinc include shellfish, red meat, beans, legumes, eggs, and dairy.

Gastrointestinal reflux disease (GERD) is a common disorder in which the lower esophageal sphincter (LES) opens inappropriately, allowing acid to backflow from the stomach into the esophagus. Normally, the LES is a one-way valve. For reasons not entirely clear, the sphincter muscle will suddenly relax, triggering symptoms of acid reflux, including:

• Heartburn
• Chest pain
• A sour or bitter taste
• Bad breath
• A burning in the throat
• Difficulty swallowing
• A lump in the throat sensation
• Coughing
• Hoarseness

GERD can usually be pinpointed as the cause of a sour or bitter taste as it typically co-occurs with heartburn and will develop soon after eating. Smoking, alcohol, caffeine, fatty foods, acidic foods, and eating large meals are common triggers for acid reflux.

Pregnancy and obesity can contribute by placing excessive stress on the stomach and esophagus. (A hiatal hernia can have a similar effect by manipulating the position of the LES so that it is less able to remain shut.)

Diagnosis and Treatment

The diagnosis of GERD may include endoscopy to examine the LES directly; manometry to measure the contractions of the esophageal muscles; and an ambulatory pH probe in which a swallowed probe measures how and when reflux occurs.

Treatment typically involves a combination of over-the-counter and prescription medications, including antacids, H2 blockers like Prilosec (omeprazole), proton pump inhibitors like Nexium (esomeprazole), and a drug called baclofen to help strengthen the LES muscles. Changes in diet, weight loss, and the cessation of smoking can also help.

Once the GERD symptoms are controlled, the sour or bitter taste sensations should also dissipate.

Other conditions may directly alter a person's taste perception or further enhance an existing dysgeusic disorder. These include:

• Cigarette smoking, which dulls the taste and makes food less palatable
• Xerostomia (dry mouth syndrome), a condition in which decreased saliva production impairs taste perception
• Dehydration, which can directly cause xerostomia
• Anxiety and stress, both of which can alter taste perception and promote xerostomia
• Infection or illness, in which inflammation can sometimes amplify a person's perception of bitter tastes
• Oral candidiasis (thrush), a common fungal infection
• Poor dental hygiene
• Pregnancy, especially during the first trimester
• Menopause, which, like pregnancy, may cause dysgeusia due to changes in hormone levels
• Brain injury or surgery, particularly in the midbrain or thalamus region, which can trigger "phantom" taste sensations
• Neurologic disorders such as epilepsy, multiple sclerosis, Bell's palsy, brain tumors, and dementia
• Radiation therapy of the head and neck, which can damage salivary tissues
• Lead poisoning, often recognized by a characteristic blue line along the gums
• Pine nut syndrome, a poorly understood condition in which a bitter taste may occur one to three days after eating pine nuts

Whatever the underlying cause of dysgeusia, there are things you can do to help minimize the symptoms. Among some of the more practical home remedy tips:

• Drink plenty of water, which can improve dry mouth and promote urination (the latter of which can improve drug clearance if you are dehydrated). Adding a little lemon juice may also help reduce the foul taste.
• Chew sugar-free gum to promote salivation.
• Practice good oral hygiene, including regular dental checkups, and consider using an antibacterial mouthwash.
• Some people recommend rinsing your mouth with a half-teaspoon of salt plus a teaspoon of baking soda added to a glass of water.
• Avoid spicy or fatty foods that promote acid reflux. Even if GERD is not the cause, the reflux of stomach acids will only worsen your symptoms.
• Stop smoking. Whatever the underlying cause of dysgeusia, smoking will only amplify the effects. No matter how long you have smoked, your taste perception will invariably improve once you've stopped.