Tongue diseases can be congenital or acquired. Glossitis

Glossitis

Glossitis is inflammation of the tongue. It causes the tongue to swell and change color. Finger-like projections on the surface of the tongue may be lost, causing the tongue to appear smooth....

 is a general term for tongue inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

, which can be caused by various etiologies

Etiology

Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....

 such as infection

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

.

The condition of the tongue

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

 provide information about many other conditions, as in strawberry tongue

Strawberry tongue

Strawberry tongue is the appearance of tongue with inflamed red papillae, giving an appearance suggestive to a red strawberry.-Associated conditions:It is seen in Kawasaki disease, toxic shock syndrome, and scarlet fever....

.

Assessment of the tongue has historically been an important part of a medical examination.

Examples include:

• White tongue: White
  White
  White is a color, the perception of which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in nearly equal amounts and with high brightness compared to the surroundings. A white visual stimulation will be void of hue and grayness.White light can be...
  
   spots and patches or coating of the tongue are a symptom
  Symptom
  A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
  
   of several medical conditions:
  • Antibiotics side effect
    Adverse effect (medicine)
    In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
    
    
  • Oral candidiasis
    Oral candidiasis
    Oral candidiasis is an infection of yeast fungi of the genus Candida on the mucous membranes of the mouth. It is frequently caused by Candida albicans, or less commonly by Candida glabrata or Candida tropicalis...
    
     that may be associated with medication
    Medication
    A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
    
    s (such as local or systemic antibiotic
    Antibiotic
    An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
    
    s, and corticosteroid
    Corticosteroid
    Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
    
    s), immunodeficiency
    Immunodeficiency
    Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...
    
     (such as HIV
    HIV
    Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
    
    , diabetes mellitus
    Diabetes mellitus
    Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
    
    ) and tongue piercing
    Tongue piercing
    A tongue piercing is a body piercing usually done directly through the center of the tongue, and is the most popular piercing site in the western world after the ear and nostril.-History and culture:...
    
    .
  • Dehydration
    Dehydration
    In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
    
    
  • Leukoplakia
    Leukoplakia
    Leukoplakia is a clinical term used to describe patches of keratosis. It is visible as adherent white patches on the mucous membranes of the oral cavity, including the tongue, but also other areas of the gastro-intestinal tract, urinary tract and the genitals. The clinical appearance is highly...
    
    
  • Keratosis pharyngis
    Keratosis pharyngis
    Keratosis pharyngis is a medical condition where keratin grows on the surface of the pharynx, that is the part of the throat at the back of the mouth...
    
    
  • Jaundice
    Jaundice
    Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
    
     - causes a yellow tongue
  • "Lie Bumps
    Lie bumps
    Lie bumps are painful, hypertrophic, red and white papillae on the tongue.- Cause :The name "lie bumps" is a result of a myth stating that telling a lie would cause one....
    
    " - small dots usually on tip of tongue
• Geographic tongue
  Geographic tongue
  Geographic tongue, an inflammatory condition of the tongue affecting approximately 2% of the population, is characterized by discolored regions of taste buds or sometimes even cracks in the tongue...
  
  . This is very common condition that affects the anterior two thirds of the dorsal and lateral tongue mucosa of 1% to 2.5% of the population. When lesions involve other oral mucosa in addition to the dorsal and lateral tongue, the condition is called migratory stomatitis
  Migratory stomatitis
  Migratory stomatitis is a benign condition on the oral soft tissue. This condition has two forms: the common form, which is consisted from red lesions with white borders on the tongue only. This form is called geographic tongue...
  
   (or ectopic geographic tongue); in this uncommon condition, lesions infrequently involve also the ventral tongue and buccal or labial mucosa, the soft palate
  Soft palate
  The soft palate is the soft tissue constituting the back of the roof of the mouth. The soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone....
  
   and floor of the mouth. Although this condition is considered a normal variant rather than pathology, it occasionally symptomatic.
• Hypoglossia
  Hypoglossia
  Hypoglossia is a short, incompletely developed tongue. It can occur either as an isolated malformation or in association with other deformities, particularly limb defects in a syndrome known as oromandibular limb hypogenesis syndrome.-References:...
  
   - congenitally short tongue
• Tongue necrosis
  Necrosis
  Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
  
   owing to local or systemic ischemic
  Ischemia
  In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
  
   conditions, most commonly giant cell arteritis.
• Squamous cell carcinoma
  Oral cancer
  Oral cancer is a subtype of head and neck cancer, is any cancerous tissue growth located in the oral cavity. It may arise as a primary lesion originating in any of the oral tissues, by metastasis from a distant site of origin, or by extension from a neighboring anatomic structure, such as the...
  
  

The tongue is examined and observed diagnostically in traditional Chinese medicine

Traditional Chinese medicine

Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...

. A painful tongue may be an indication of several underlying serious medical conditions