Tongue discomfort includes both pain and burning sensations, often caused by irritation.
(See also table Oral Findings in Systemic Disorders Oral Findings in Systemic Disorders 
in topic Systemic Disorders and the Mouth Systemic Disorders and the Mouth Clues suggesting systemic disease may be found in the mouth and adjacent structures (see Introduction to the Approach to the Dental Patient and table Oral Findings in Systemic Disorders). A... read more .)
The most common causes of tongue discomfort are
Certain foods, especially acidic ones (eg, pineapple)
Certain ingredients in toothpaste, mouthwash, candy, or gum
Certain drugs (commonly, those that cause dry mouth: antihistamines Treatment Allergic (including atopic) and other hypersensitivity disorders are inappropriate or exaggerated immune reactions to foreign antigens. Inappropriate immune reactions include those that are... read more , antipsychotics Treatment Schizophrenia is characterized by psychosis (loss of contact with reality), hallucinations (false perceptions), delusions (false beliefs), disorganized speech and behavior, flattened affect... read more , tricyclic antidepressants; Heterocyclic Antidepressants Several drug classes and drugs can be used to treat depression: Selective serotonin reuptake inhibitors (SSRIs) Serotonin modulators (5-HT2 blockers) Serotonin-norepinephrine reuptake inhibitors... read more less commonly, angiotensin-converting enzyme inhibitors, nonsteroidal anti-inflammatory drugs, or chemotherapeutic agents such as methotrexate, bleomycin, 5-fluorouracil)
Accidental trauma to tongue during mastication or due to nocturnal bruxism Bruxism Bruxism is clenching or grinding of teeth. Bruxism can occur during sleep (sleep bruxism) and while awake (awake bruxism). In some people, bruxism causes headaches, neck pain, and/or jaw pain... read more , or trauma from broken restorations or sharp teeth
Other causes of tongue discomfort include
Atrophic glossitis
Submandibular space infection Submandibular Space Infection Submandibular space infection is acute cellulitis of the soft tissues below the mouth. Symptoms include pain, dysphagia, and potentially fatal airway obstruction. Diagnosis usually is clinical... read more
(Ludwig's angina): involves sublingual, submandibular and submental spaces and can cause elevation of tongue.Celiac disease Celiac Disease Celiac disease is an immunologically mediated disease in genetically susceptible people caused by intolerance to gluten, resulting in mucosal inflammation and villous atrophy, which causes malabsorption... read more
(tongue is most commonly affected oral site, presents as painful burning sensation)
Atrophic glossitis sometimes causes a burning sensation of the tongue; it has many causes, including deficiency of iron Iron Deficiency Iron (Fe) is a component of hemoglobin, myoglobin, and many enzymes in the body. Heme iron is contained mainly in animal products. It is absorbed much better than nonheme iron (eg, in plants... read more or vitamin B12 Vitamin B12 Deficiency Dietary vitamin B12 deficiency usually results from inadequate absorption, but deficiency can develop in vegans who do not take vitamin supplements. Deficiency causes megaloblastic anemia, damage... read more and dry mouth (xerostomia Xerostomia Xerostomia is dry mouth caused by reduced or absent flow of saliva. This condition can result in discomfort, interfere with speech and swallowing, make wearing dentures difficult, cause halitosis... read more ). Burning mouth syndrome Burning Mouth Syndrome Burning mouth syndrome is a chronic condition of burning intraoral pain, usually involving the tongue, in the absence of an identified cause. There are no physical signs or specific diagnostic... read more causes no visible signs, but patients have burning pain and paresthesia of the tongue, usually, and of the mouth and lips.
Evaluation of tongue discomfort must first exclude submandibular space infection Submandibular Space Infection Submandibular space infection is acute cellulitis of the soft tissues below the mouth. Symptoms include pain, dysphagia, and potentially fatal airway obstruction. Diagnosis usually is clinical... read more , which is life-threatening due to potential airway obstruction. Many other causes, such as a sharp tooth edge or candidiasis Candidiasis (Mucocutaneous) Candidiasis is skin and mucous membrane infection with Candida species, most commonly Candida albicans. Infections can occur anywhere and are most common in skinfolds, digital... read more 
, are readily apparent on examination. Identifying irritant causes often requires sequential elimination of possible causes. Burning mouth syndrome is a diagnosis of exclusion once other causes have been ruled out.
Tongue discomfort not caused by infection is usually treated by eliminating the cause (eg, changing brands of toothpaste, particularly to a brand that does not contain sodium lauryl sulfate), avoiding irritating/acidic/spicy foods, or having a sharp or broken tooth repaired. Warm salt-water rinses may help. Identified underlying conditions are treated.
