The inside of the mouth is lined with a thin epithelium known as the the oral mucosa. It is highly sensitive to temperature, chemicals and even physical stimulants, coupled with the tongue which is one of the most sensitive parts of the body. This is partly due to the network of nerves supplying the mouth and tongue as well as the thin mucosa which does not act as much of a physical barrier as the skin. Therefore any injury, whether chemical or mechanical, can cause pain within the mouth. Sometimes this mouth pain is experienced as a burning sensation yet not pain or it may be a burning pain. This often signifies injury to the oral mucosa with ongoing irritation or damage of the tissue. However, in some cases there is no obvious cause of this burning mouth sensation and even diagnostic investigations cannot reveal a definitive reason for this sensation.
What is burning mouth syndrome?
Burning mouth syndrome (BMS) is a condition of the mouth marked by an intense and continuous burning sensation of the tongue, inside of the mouth (oral mucosa) and lips. The pain is primarily centered on the tongue and extends outwards to the oral mucosa and lips. It may also involve the gums and palate (roof of the mouth). There is no definitive known cause of burning mouth syndrome in most cases. Many patients with burning mouth syndrome reports some disturbances with the sense of taste (dysgeusia ~ unusual taste; parageusia ~ diminished taste) and there may also be dryness of the mouth.
Types of Burning Mouth Syndrome
Burning mouth syndrome can also be classified according to the symptoms that are present.
The symptoms of this type of burning mouth syndrome may be seen with conditions like nutritional deficiencies and diabetes mellitus.
- No symptoms present upon waking in the morning.
- Symptoms gradually appear and progress throughout the day.
- Nighttime symptoms may ease or worsen.
The symptoms may be linked to chronic anxiety.
- No symptoms at night.
- Persistent symptoms throughout the day.
The symptoms of this type of burning mouth syndrome may be associated with a food allergy.
- Intermittent symptoms on some days.
- Symptom-free on other days.
Causes of Burning Mouth Syndrome
Burning mouth syndrome can be broadly classified as :
- Primary where the condition exists without any underlying disease and the exact cause is largely unknown.
- Secondary where the condition arises possibly due to some other underlying disorder.
Although the exact cause of primary burning mouth syndrome is unknown, there have been many theories proposed as to why it may occur. In the past it was believed to be psychogenic meaning that it has no physical etiology but is rather psychological in origin. These days it is believed that the condition is due to a nerve dysfunction (neuropathic). It appears that some disorder with the pain fibers and trigeminal nerve may be account for burning mouth syndrome.
Sometimes burning mouth syndrome occurs in the backdrop of other diseases. The exact link between the underlying disease and burning mouth syndrome is not always clear. Burning mouth syndrome is a long term condition. Therefore chronic diseases are the more likely secondary causes.
- Dry mouth (xerostomia) which is ongoing either related to the use of chronic medication or with salivary gland problems.
- Gastroesophageal reflux disease (GERD) where the stomach acid flows backwards into the esophagus and may reach the mouth.
- Infections such as herpetic stomatitis or oral candidiasis (thrush in the mouth) which tend to be persistent particularly in patients with HIV/AIDS and diabetes mellitus.
- Nutritional deficiencies associated with a lack of cobalamin, iron, folate, pyridoxine, riboflavin and thiamin – mainly the B-group of vitamins.
- Food allergies where the body’s immune system causes localized inflammation as a result of hyper-reacting to certain foods and drinks.
- Dentures – ill-fitting dentures and denture stomatitis. Since dentures are used over a long period, the condition tends to persist.
- Damage to the nerves supplying the tongue and mouth.
- Changes in hormone levels seen with certain phases in life such as menopause.
- Disorders of the glands and hormones as is seen with diabetes mellitus or hypothyroidism.
- Certain chronic medication like high blood pressure medication or drugs for psychiatric disorders.
- Mental health ailments such as depression and anxiety.
Other Causes of Burning Mouth
Picture from Dermatology Atlas,
courtesy of Samuel Freire da Silva, M.D.
Many of the conditions that cause burning mouth syndrome have been discussed in the context of secondary causes which are largely chronic diseases. Sometimes a burning mouth pain is short-lived and only triggered by certain situations. These acute causes of burning mouth pain cannot be seen as burning mouth syndrome.
- Overzealous brushing especially of the tongue and use of harsh mouthwashes particularly those brands with alcohol.
- Tobacco chewing, areca nut and betel leaf chewing.
- Some chewable nutritional supplements.
- Spicy foods and other food additives which may irritate the mouth.
- Alcoholic beverages, particularly strong liquor like home brews.
- Certain narcotics particularly when ingested or smoked.
- Accidental or intentional poisoning particularly with drinking strong corrosives.
- Following dental procedures and as anesthesia wears off.
- Immediately after tongue piercings and sometimes for a short while thereafter.
Signs and Symptoms
A burning sensation in the mouth is a symptom and not a disease on its own. However, it may be accompanied by other symptoms particularly with burning mouth syndrome. The intensity, duration and nature of these symptoms may vary as discussed under the different types of burning mouth syndrome.
- Paresthesias such as tingling, prickling or numbness of the tongue, mouth and lips.
- Dryness of the mouth
- Increased thirst
- Loss of taste
- Abnormalities of the tongue surface such as marks, unusual projections, ulcers, discoloration and so on. Geographic tongue may sometimes accompany burning mouth syndrome.
Treatment of Burning Mouth Syndrome
Primary burning mouth syndrome is difficult to treat as the exact cause is unknown. With secondary burning mouth syndrome, treatment should be directed at the underlying condition. Some of the treatment and management measures include :
- Medication for anxiety and depression including selective serotonin reputake inhibitors (SSRIs). tricyclic antidepressants and benzodiazepines.
- Anaesthetics particularly topical dental varieties and other topical pain relieving agents like capsaicin (topical).
- Hormone replacement therapy.
- Antioxidants like alpha-lipoic acid and capsaicin (oral).
- Vitamin B supplements.
- Seizure / epilepsy medication.
- Certain mouthwashes.