Hairy tongue largely occurs in the central part of the dorsal tongue, just anterior (in front) of the circumvallate papillae, although sometimes the entire dorsal surface may be involved. Discoloration usually accompanies hairy tongue, and may be yellow, brown or black. Apart from the appearance, the condition is typically asymptomatic, but sometimes people may experience a gagging sensation or a bad taste. There may also be associated oral malodor (intra-oral halitosis).

Depending upon what exact meaning of the word glossitis is implied, signs and symptoms might include:

- Smooth, shiny appearance of the tongue, caused by loss of lingual papillae.

- Tongue color changes, usually to a darker red color than the normal white-pink color of a healthy tongue.

- Tongue swelling.

- Difficulty with chewing, swallowing, or speaking (either because of tongue soreness of tongue swelling).

- Burning sensation. Some use the term secondary burning mouth syndrome in cases where a detectable cause, such as glossitis, for an oral burning sensation.

Depending upon the underlying cause, there may be additional signs and symptoms such as pallor, oral ulceration and angular cheilitis.

Black hairy tongue (BHT, also termed lingua villosa nigra) refers to a condition of the tongue where the filiform papillae elongate with black or brown discoloration, giving a black and hairy appearance. The appearance may be alarming, but it is a harmless condition. Predisposing factors include smoking, xerostomia (dry mouth), soft diet, poor oral hygiene and certain medications. Management is by improving oral hygiene, especially scraping or brushing the tongue.

Geographic tongue, also termed benign migratory glossitis, is a common condition which usually affects the dorsal surface of the tongue. It is characterized by patches of depapillation and erythema bordered by a whitish peripheral zone. These patches give the tongue the appearance of a map, hence the name. Unlike glossitis due to nutritional deficiencies and anemia, the lesions of geographic tongue move around the tongue over time. This is because in geographic tongue, new areas of the tongue become involved with the condition whilst previously affected areas heal, giving the appearance of a moving lesion. The cause is unknown, and there is no curative treatment. Rarely are there any symptoms associated with the lesions, but occasionally a burning sensation may be present, which is exacerbated by eating hot, spicy or acidic foodstuffs. Some consider geographic tongue to be an early stage of fissured tongue, since the two conditions often occur in combination.

In health, the dorsal surface of the tongue is covered in tuft like projections called lingual papillae (some of which are associated with taste buds), which give the tongue an irregular surface texture and a white-pink color. Geographic tongue is characterized by areas of atrophy and depapillation (loss of papillae), leaving an erythematous (darker red) and smoother surface than the unaffected areas. The depapillated areas are usually well demarcated, and bordered by a slightly raised, white, yellow or grey, serpiginous (snaking) peripheral zone. A lesion of geographic tongue may start as a white patch before the depapillation occurs. In certain cases there may be only one lesion, but this is uncommon; the lesions will typically occur in multiple locations on the tongue and coalesce over time to form the typical map-like appearance. The lesions usually change in shape, size and migrate to other areas, sometimes within hours. The condition may affect only part of the tongue, with a predilection for the tip and the sides of the tongue, or the entire dorsal surface at any one time. The condition goes through periods of remission and relapse. Loss of the white peripheral zone is thought to signify periods of mucosal healing.

There are usually no symptoms other than the unusual appearance of the tongue, but in some cases persons may experience pain or burning e.g. when eating hot, acidic, spicy or other kinds of foods (e.g. cheese, tomatoes, fruit). Where there is a burning symptom, other causes of a burning sensation on the tongue are considered, such as oral candidiasis.

The lesions are located on the mucosa, usually bilaterally in the central part of the anterior buccal mucosa and along the level of the occlusal plane (the level at which the upper and lower teeth meet). Sometimes the tongue or the labial mucosa (the inside lining of the lips) is affected by a similarly produced lesion, termed morsicatio linguarum and morsicatio labiorum respectively. There may be a coexistent linea alba, which corresponds to the occlusal plane, or crenated tongue. The lesions are white with thickening and shredding of mucosa commonly combined with intervening zones of erythema (redness) or ulceration. The surface is irregular, and people may occasionally have loose sections of mucosa that comes away.

Plasma cell cheilitis is a very rare presentation of a condition which more usually occurs on the gingiva (termed "plasma cell gingivitis") or sometimes the tongue. Plasma cell cheilitis appears as well defined, infiltrated, dark red plaque with a superficial lacquer-like glazing. Plasma cell cheilitis usually involves the lower lip. The lips appear dry, atrophic and fissured. Angular cheilitis is sometimes also present.

The name "lie bumps" is a result of a myth that telling lies would cause them. However, very little has been written about this condition in scientific articles or textbooks and scientific studies have failed to produce a definite cause. Possible causes include: "stress, gastrointestinal upset, menstruation, acidic or sour food, smoking, and local trauma" (direct physical irritation) of the tongue. Lie bumps are often caused by the taste bud(s) splitting.

These bumps are small, white bumps on the base of the tongue. They are likely to be the result of transient lingual papillitis (TLP). This condition is limited to the upper (dorsal) surface of the tongue, affecting some of the tiny bumps on the tongue known as the fungiform papillae, what we commonly call the "taste buds."

TLP is a harmless problem. These bumps can become notably red or white and are quite tender for up to several days. While the cause of TLP is not known with certainty, most experts feel that local accidental trauma (rubbing, scraping or biting) is a major factor; however, contact reactions to things like certain foods have also been suggested. Lie bumps are not contagious and the discomfort is relatively minor. Typically these lesions heal within a few days with no treatment, though a doctor may refer a patient to an oral pathologist in prolonged cases.

Geographic tongue, also known by several other terms, is an inflammatory condition of the mucous membrane of the tongue, usually on the dorsal surface. It is a common condition, affecting approximately 2–3% of the general population. It is characterized by areas of smooth, red depapillation (loss of lingual papillae) which migrate over time. The name comes from the map-like appearance of the tongue, with the patches resembling the islands of an archipelago. The cause is unknown, but the condition is entirely benign (importantly, it does not represent oral cancer), and there is no curative treatment. Uncommonly, geographic tongue may cause a burning sensation on the tongue, for which various treatments have been described with little formal evidence of efficacy.

The cause is chronic parafunctional activity of the masticatory system, which produces frictional, crushing and incisive damage to the mucosal surface and over time the characteristic lesions develop. Most people are aware of a cheek chewing habit, although it may be performed subconsciously. Sometimes poorly constructed prosthetic teeth may be the cause if the original bite is altered. Usually the teeth are placed too far facially (i.e. buccally and/or labially), outside the "neutral zone", which is the term for the area where the dental arch is usually situated, where lateral forces between the tongue and cheek musculature are in balance. Glassblowing involves chronic suction and may produce similar irritation of the buccal mucosa. Identical, or more severe damage may be caused by self-mutilation in people with psychiatric disorders, learning disabilities or rare syndromes (e.g. Lesch-Nyhan syndrome and familial dysautonomia).

Examples of congenital disorders which affect the tongue include:

- Aglossia - complete absence of the tongue at birth

- Ankyloglossia (tongue tie) - where the lingual frenum tethers the tongue to the floor of the mouth. If it interferes with oral hygiene and feeding, frenectomy may be indicated.

- Hypoglossia - congenitally short tongue

- Microglossia

- Macroglossia - an abnormally large tongue, seen in some disorders such as Down syndrome (although macroglossia can be an acquired condition as well).

- Hamartomata - for example Leiomyomatous hamartoma

- Glossoptosis

- Choristomata - For example, osseous choristoma of the tongue, a very rare condition characterized by a nodule on the dorsum of the tongue containing mature lamellar bone without osteoblastic or osteoclastic activity. Cartilagenous (chondroid), and glial choristomas may also very rarely occur on the tongue.

- Lingual thyroid

- Cleft tongue (bifid tongue) - completely cleft tongue is a rare condition caused by a failure of the lateral lingual swellings to merge. More common is an incompletely cleft tongue, appearing as midline fissure. This is normally classed as fissured tongue.

Transient lingual papillitis (also termed fungiform papillary glossitis,

eruptive lingual papillitis, or colloquially, lie bumps), are painful, hypertrophic, red and white on the tongue.

Crenated tongue (also called scalloped tongue, pie crust tongue, lingua indentata, or crenulated tongue) is a descriptive term for the appearance of the tongue when there are indentations along the lateral borders (the sides), as the result of compression of the tongue against the adjacent teeth.

The oral mucosa in the area of crenation is usually of normal color, but there may be erythema (redness) if exposed to a high degree of friction or pressure. Crenated tongue is usually asymptomatic and harmless.

It is not a disease as such, but usually results from habits where the tongue is pressed against the lingual surfaces (the side facing the tongue) of the dental arches, or from any cause of macroglossia (enlarged tongue), which in itself has many causes such as Down syndrome.

Where crenation is caused by parafunctional habits, there may also be associated bruxism, linea alba, or morsicatio buccarum.

Common causes of drug-related cheilitis include Etretinate, Indinavir, Protease inhibitors, Vitamin A and Isotretinoin (a retinoid drug). Uncommon causes include Atorvastatin, Busulphan, Clofazimine, Clomipramine, Cyancobalamin, Gold, Methyldopa, Psoralens, Streptomycin, Sulfasalazine and Tetracycline. A condition called "drug-induced ulcer of the lip" is described as being characterized by painful or tender, well-defined ulcerations of the lip without induration. It is the result of oral administration of drugs, and the condition resolves when the drugs are stopped.

Also called smoker's palatal keratosis, this condition may occur in smokers, especially pipe smokers. The palate appears dry and cracked, and white from keratosis. The minor salivary glands appear as small, red and swollen bumps. It is not a premalignant condition, and the appearance reverses if the smoking is stopped.

The term "necrotizing ulcerative gingivostomatitis" is sometimes used as a synonym of the necrotizing periodontal disease more commonly termed necrotizing ulcerative gingivitis, or a more severe form (also termed necrotizing stomatitis). The term "necrotizing gingivostomatitis" is also sometimes used.

Tongue diseases can be congenital or acquired, and are multiple in number. Considered according to a surgical sieve, some example conditions which can involve the tongue are discussed below. Glossitis is a general term for tongue inflammation, which can have various etiologies, e.g. infection.

Acrocyanosis is persistent blue or cyanotic discoloration of the extremities, most commonly occurring in the hands, although it also occurs in the feet and distal parts of face.

The principal (primary) form of acrocyanosis is that of a benign cosmetic condition, sometimes caused by a relatively benign neurohormonal disorder. Regardless of its cause, the benign form typically does not require medical treatment. A medical emergency would ensue if the extremities experience prolonged periods of exposure to the cold, particularly in children and patients with poor general health. However, frostbite differs from acrocyanosis because pain (via thermal nociceptors) often accompanies the former condition, while the latter is very rarely associated with pain. There are also a number of other conditions that affect hands, feet, and parts of the face with associated skin color changes that need to be differentiated from acrocyanosis: Raynaud’s phenomenon, pernio, acrorygosis, erythromelalgia, blue finger syndrome. The diagnosis may be challenging in some cases, especially when these syndromes co-exist.

Acrocyanosis may be a sign of a more serious medical problem, such as connective tissue diseases and diseases associated with central cyanosis. Other causative conditions include infections, toxicities, antiphospholipid syndrome, cryoglobulinemia, neoplasms. In these cases, the observed cutaneous changes are known as "secondary acrocyanosis". They may have a less symmetric distribution and may be associated with pain and tissue loss.

Poikiloderma of Civatte is a cutaneous condition and refers to reticulated red to red-brown patches with telangiectasias. It is identifiable as the reddish brown discoloration on sides of the neck, usually on both sides. It is more common with women than men and more commonly effects middle-aged to elderly women. "Poikiloderma" is basically a change of the skin due to dilation of the blood vessels in the neck. "Civatte" was the French dermatologist who first identified it in the 1920s.

Caviar tongue (also termed sublingual varicosities or sublingual varices), is a condition characterized by purplish venous ectasias commonly found on the ventral (undersurface) of the tongue after the age of fifty. It is normal for there to be veins visible underneath the tongue, partly because the mucous membrane is so thin and translucent in this region, but where these vessels become dilated and tortuous, they may appear round and black like caviar.

The clinical appearance is considerably varied in both the orientation, number, depth and length of the fissure pattern. There are usually multiple grooves/furrows 2–6 mm in depth present. Sometimes there is a large central furrow, with smaller fissures branching perpendicularly. Other patterns may show a mostly dorsolateral position of the fissures (i.e. sideways running grooves on the tongue's upper surface). Some patients may experience burning or soreness.

Bismuthia is a rare dermatological condition that results from the prolonged use of bismuth.

Much more rarely than with silver, bismuth may produce a generalized persistent skin discoloration resembling argyria. This is known as bismuthia. The conjunctivae and oral mucosa, as well as skin, are commonly afflicted by the condition. Pigment granules are evenly scattered through the dermis, producing a blue, or bluish gray skin color by the scattering phenomenon. It is extremenly rare, and as a consequence is poorly understood by modern medicine. Special stains and spectroscopic methods must be utilized for identification of skin pigments affected by bismuth.

Usually, bismuth produces a black line, due to bismuth sulfide, along the gums, near the teeth, similar to a lead line. This is not likely to occur if the gum is edentulous or the gum and the teeth normal. It is more common when gingivitis and carious teeth are present. Bismuth excess may cause stomatitis. On even rarer occasions, bismuth has been reported to cause pigmentation of the vagina and cervix.

The symptoms of melasma are dark, irregular well demarcated hyperpigmented macules to patches commonly found on the upper cheek, nose, lips, upper lip, and forehead. These patches often develop gradually over time. Melasma does not cause any other symptoms beyond the cosmetic discoloration. Melasma is also common in pre-menopausal women. It is thought to be enhanced by surges in certain hormones.

Acrocyanosis is characterized by peripheral cyanosis: persistent cyanosis of the hands or of the hands, feet, or face. The extremities often are cold and clammy and may exhibit some swelling (especially in the warmer weather). The palms and soles exhibit a wide range of sweating from moderately moist to profuse, but all peripheral pulses should have normal rate, rhythm, and quality. Exposure to cold temperatures worsens the cyanosis, while it often improves on warming. Aside from the color changes, patients normally are asymptomatic and therefore there is usually no associated pain. The most common sign, discoloration, usually is what prompts patients to seek medical care.

By definition, BMS has no signs. Sometimes affected persons will attribute the symptoms to sores in the mouth, but these are in fact normal anatomic structures (e.g. lingual papillae, varices). Symptoms of BMS are variable, but the typical clinical picture is given below, considered according to the Socrates pain assessment method (see table). If clinical signs are visible, then another explanation for the burning sensation may be present. Erythema (redness) and edema (swelling) of papillae on the tip of the tongue may be a sign that the tongue is being habitually pressed against the teeth. The number and size of filiform papillae may be reduced. If the tongue is very red and smooth, then there is likely a local or systemic cause (e.g. eythematous candidiasis, anemia).