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).

True hyposalivation may give the following signs and symptoms:

- Dental caries (xerostomia related caries) – Without the anticariogenic actions of saliva, tooth decay is a common feature and may progress much more aggressively than it would otherwise ("rampant caries"). It may affect tooth surfaces that are normally spared, e.g., cervical caries and root surface caries. This is often seen in patients who have had radiotherapy involving the major salivary glands, termed radiation-induced caries.

- Acid erosion. Saliva acts as a buffer and helps to prevent demineralization of teeth.

- Oral candidiasis – A loss of the antimicrobial actions of saliva may also lead to opportunistic infection with "Candida" species.

- Ascending (suppurative) sialadenitis – an infection of the major salivary glands (usually the parotid gland) that may be recurrent. It is associated with hyposalivation, as bacteria are able to enter the ductal system against the diminished flow of saliva. There may be swollen salivary glands even without acute infection, possibly caused by autoimmune involvement.

- Dysgeusia – altered taste sensation (e.g., a metallic taste) and dysosmia, altered sense of smell.

- Intraoral halitosis – possibly due to increased activity of halitogenic biofilm on the posterior dorsal tongue (although dysgeusia may cause a complaint of nongenuine halitosis in the absence of hyposalivation).

- Oral dysesthesia – a burning or tingling sensation in the mouth.

- Saliva that appears thick or ropey.

- Mucosa that appears dry.

- A lack of saliva pooling in the floor of the mouth during examination.

- Dysphagia – difficulty swallowing and chewing, especially when eating dry foods. Food may stick to the tissues during eating.

- The tongue may stick to the palate, causing a clicking noise during speech, or the lips may stick together.

- Gloves or a dental mirror may stick to the tissues.

- Fissured tongue with atrophy of the filiform papillae and a lobulated, erythematous appearance of the tongue.

- Saliva cannot be "milked" (expressed) from the parotid duct.

- Difficulty wearing dentures, e.g., when swallowing or speaking. There may be generalized mucosal soreness and ulceration of the areas covered by the denture.

- Mouth soreness and oral mucositis.

- Lipstick or food may stick to the teeth.

- A need to sip drinks frequently while talking or eating.

- Dry, sore, and cracked lips and angles of mouth.

- Thirst.

However, sometimes the clinical findings do not correlate with the symptoms experienced. E.g., a person with signs of hyposalivation may not complain of xerostomia. Conversely a person who reports experiencing xerostomia may not show signs of reduced salivary secretions (subjective xerostomia). In the latter scenario, there are often other oral symptoms suggestive of oral dysesthesia ("burning mouth syndrome"). Some symptoms outside the mouth may occur together with xerostomia.

These include:

- Xerophthalmia (dry eyes).

- Inability to cry.

- Blurred vision.

- Photophobia (light intolerance).

- Dryness of other mucosae, e.g., nasal, laryngeal, and/or genital.

- Burning sensation.

- Itching or grittiness.

- Dysphonia (voice changes).

There may also be other systemic signs and symptoms if there is an underlying cause such as Sjögren's syndrome, for example, joint pain due to associated rheumatoid arthritis.

Burning mouth syndrome (BMS) is a burning sensation in the mouth with no underlying dental or medical cause. No related signs of disease are found in the mouth. People with burning mouth syndrome may also have a dry mouth sensation where no cause can be found such as reduced salivary flow, tingling in the mouth, or an altered taste or smell.

A burning sensation in the mouth can be a symptom of another disease when local or systemic factors are found to be implicated, and this is not considered to be burning mouth syndrome, which is a syndrome of medically unexplained symptoms. The International Association for the Study of Pain defines burning mouth syndrome as "a distinctive nosological entity characterized by unremitting oral burning or similar pain in the absence of detectable mucosal changes", and "burning pain in the tongue or other oral mucous membranes", and the International Headache Society defines it as "an intra-oral burning sensation for which no medical or dental cause can be found".

Due to insufficient evidence it is unclear if effective treatments exist.

The differential of hyposalivation significantly overlaps with that of xerostomia. A reduction in saliva production to about 50% of the normal unstimulated level will usually result in the sensation of dry mouth. Altered saliva composition may also be responsible for xerostomia.

Cancer patients undergoing chemotherapy usually become symptomatic four to five days after beginning treatment, reaching a peak at around day 10, and then slowly improving over the course of a few weeks. Mucositis associated with radiotherapy usually appears at the end of the second week of treatment and may last for six to eight weeks.

As a result of cell death in reaction to chemo- or radio-therapy, the mucosal lining of the mouth becomes thin, may slough off and then become red, inflamed and ulcerated. The ulcers may become covered by a yellowish white fibrin clot called a pseudomembrane. Peripheral erythema is usually present. Ulcers may range from 0.5 cm to greater than 4 cm. Oral mucositis can be severely painful. The degree of pain is usually related to the extent of the tissue damage. Pain is often described as a burning sensation accompanied by reddening. Due to pain, the patient may experience trouble speaking, eating, or even opening the mouth.

Dysgeusia, or an alteration in taste perception, is common, especially for those who are receiving concomitant radiation therapy to the neck and mouth area. "Taste blindness", or an altered sense of taste, is a temporary condition that occurs because of effects on taste buds that are mostly located in the tongue. Sometimes, only partial recovery of taste occurs. Common complaints are of food tasting too sweet or too bitter or of a continuous metallic taste.

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.

Orofacial granulomatosis is enlargement of lips due to the formation of non-caseating granulomatous inflammation, which obstruct lymphatic drainage of the orofacial soft tissues, causing lymphedema. Essentially, granulomatous cheilitis refers to the lip swelling that accompanies this condition. "Median cheilitis" may be seen, which is fissuring in the midline of the lips due to the enlargement of the lips. Angular cheilitis may also be associated with orofacial granulomatosis.

A related condition is Melkersson–Rosenthal syndrome, a triad of facial palsy, chronic lip edema, and fissured tongue. "Miescher’s cheilitis", and "granulomatous macrocheilitis", are synonyms of granulomatous cheilitis.

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.

Atrophic glossitis, also known as bald tongue, smooth tongue, Hunter glossitis, Moeller glossitis, or Möller-Hunter glossitis, is a condition characterized by a smooth glossy tongue that is often tender/painful, caused by complete atrophy of the lingual papillae (depapillation). The dorsal tongue surface may be affected totally, or in patches, and may be associated with a burning sensation, pain and/or erythema. Atrophic glossitis is a non-specific finding, and has a great many causes, usually related to iron-deficiency anemia, pernicious anemia, B vitamin complex deficiencies, unrecognized and untreated celiac disease (which often presents without gastrointestinal symptoms), or other factors such as xerostomia (dry mouth). Although the terms Möller and Hunter glossitis were originally used to refer to specifically the glossitis that occurs in vitamin B12 deficiency secondary to pernicious anemia, they are now used as synonyms for atrophic glossitis generally. In this article, the term glossitis, unless otherwise specified, refers to atrophic glossitis.

Candidiasis may be a concurrent finding or an alternative cause of erythema, burning, and atrophy.

Herpetiform ulcers, (also termed stomatitis herpetiformis, or herpes-like ulcerations) is a subtype of aphthous stomatitis so named because the lesions resemble a primary infection with herpes simplex virus (primary herpetic gingivostomatitis). However, herpetiform ulceration is not caused by herpes viruses. As with all types of aphthous stomatitis, it is not contagious. Unlike true herpetic ulcers, herpetiforme ulcers are not preceded by vesicles (small, fluid filled blisters). Herpetiforme ulcers are less than 1 mm in diameter and occur in variably sized crops up to one hundred at a time. Adjacent ulcers may merge to form larger, continuous areas of ulceration. Healing occurs within fifteen days without scarring. The ulceration may affect keratinized mucosal surfaces in addition to non keratinized. Herpetiform ulceration is often extremely painful, and the lesions recur more frequently than minor or major aphthous ulcers. Recurrence may be so frequent that ulceration is virtually continuous. It generally occurs in a slightly older age group than the other subtypes, and females are affected slightly more frequently than males.

Persons with aphthous stomatitis have no detectable systemic symptoms or signs (i.e., outside the mouth). Generally, symptoms may include prodromal sensations such as burning, itching, or stinging, which may precede the appearance of any lesion by some hours; and pain, which is often out of proportion to the extent of the ulceration and is worsened by physical contact, especially with certain foods and drinks (e.g., if they are acidic). Pain is worst in the days immediately following the initial formation of the ulcer, and then recedes as healing progresses. If there are lesions on the tongue, speaking and chewing can be uncomfortable, and ulcers on the soft palate, back of the throat, or esophagus can cause painful swallowing. Signs are limited to the lesions themselves.

Ulceration episodes usually occur about 3–6 times per year. However, severe disease is characterized by virtually constant ulceration (new lesions developing before old ones have healed) and may cause debilitating chronic pain and interfere with comfortable eating. In severe cases, this prevents adequate nutrient intake leading to malnutrition and weight loss.

Aphthous ulcers typically begin as erythematous macules (reddened, flat area of mucosa) which develop into ulcers that are covered with a yellow-grey fibrinous membrane that can be scraped away. A reddish "halo" surrounds the ulcer. The size, number, location, healing time, and periodicity between episodes of ulcer formation are all dependent upon the subtype of aphthous stomatitis.

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.

Angular cheilitis is a fairly non specific term which describes the presence of an inflammatory lesion in a particular anatomic site (i.e. the corner of the mouth). As there are different possible causes and contributing factors from one person to the next, the appearance of the lesion is somewhat variable. The lesions are more commonly symmetrically present on both sides of the mouth, but sometimes only one side may be affected. In some cases, the lesion may be confined to the mucosa of the lips, and in other cases the lesion may extend past the vermilion border (the edge where the lining on the lips becomes the skin on the face) onto the facial skin. Initially, the corners of the mouth develop a gray-white thickening and adjacent erythema (redness). Later, the usual appearance is a roughly triangular area of erythema, edema (swelling) and breakdown of skin at either corner of the mouth. The mucosa of the lip may become fissured (cracked), crusted, ulcerated or atrophied. There is not usually any bleeding. Where the skin is involved, there may be radiating rhagades (linear fissures) from the corner of the mouth. Infrequently, the dermatitis (which may resemble eczema) can extend from the corner of the mouth to the skin of the cheek or chin. If "Staphylococcus aureus" is involved, the lesion may show golden yellow crusts. In chronic angular cheilitis, there may be suppuration (pus formation), exfoliation (scaling) and formation of granulation tissue.

Sometimes contributing factors can be readily seen, such as loss of lower face height from poorly made or worn dentures, which results in mandibular overclosure ("collapse of jaws"). If there is a nutritional deficiency underlying the condition, various other signs and symptoms such as glossitis (swollen tongue) may be present. In people with angular cheilitis who wear dentures, often there may be erythematous mucosa underneath the denture (normally the upper denture), an appearance consistent with denture-related stomatitis. Typically the lesions give symptoms of soreness, pain, pruritus (itching) or burning or a raw feeling.

Odynophagia (; from "-" "pain" and "" "to eat") is pain when swallowing. The pain may be felt in the mouth or throat and can occur with or without difficulty swallowing. The pain may be described as an ache, burning sensation, or occasionally a stabbing pain that radiates to the back. Odynophagia often results in inadvertent weight loss.

There are many oral and maxillofacial pathologies which are not fully understood.

- Burning mouth syndrome (BMS) is a disorder where there is a burning sensation in the mouth that has no identifiable medical or dental cause. The disorder can affect anyone but tends to occur most often in middle aged women. BMS has been hypothesized to be linked to a variety of factors such as the menopause, dry mouth (xerostomia) and allergies. BMS usually lasts for several years before disappearing for unknown reasons. Other features of this disorder include anxiety, depression and social isolation. There is no cure for this disorder and treatment includes use of hydrating agents, pain medications, vitamin supplements or the usage of antidepressants.

- Aphthous stomatitis is a condition where ulcers (canker sores) appear on the inside of the mouth, lips and on tongue. Most small canker sores disappear within 10–14 days. Canker sores are most common in young and middle aged individuals. Sometimes individuals with allergies are more prone to these sores. Besides an awkward sensation, these sores can also cause pain or tingling or a burning sensation. Unlike herpes sores, canker sores are always found inside the mouth and are usually less painful. Good oral hygiene does help but sometime one may have to use a topical corticosteroid.

- Migratory stomatitis is a condition that involves the tongue and other oral mucosa. The common migratory glossitis (geographic tongue) affects the anterior two thirds of the dorsal and lateral tongue mucosa of 1% to 2.5% of the population, with one report of up to 12.7% of the population. The tongue is often fissured, especially. in elderly individuals. In the American population, a lower prevalence was reported among Mexican Americans (compared with Caucasians and African Americans) and cigarette smokers. When other oral mucosa, beside the dorsal and lateral tongue, are involved, the term migratory stomatitis (or ectopic geographic tongue) is preferred. In this condition, lesions infrequently involve also the ventral tongue and buccal or labial mucosa. They are rarely reported on the soft palate and floor of the mouth.

Mucositis is the painful inflammation and ulceration of the mucous membranes lining the digestive tract, usually as an adverse effect of chemotherapy and radiotherapy treatment for cancer. Mucositis can occur anywhere along the gastrointestinal (GI) tract, but oral mucositis refers to the particular inflammation and ulceration that occurs in the mouth. Oral mucositis is a common and often debilitating complication of cancer treatment.

Oral and gastrointestinal (GI) mucositis affects almost all patients undergoing high-dose chemotherapy and hematopoietic stem cell transplantation (HSCT), 80% of patients with malignancies of the head and neck receiving radiotherapy, and a wide range of patients receiving chemotherapy. Alimentary tract mucositis increases mortality and morbidity and contributes to rising health care costs.

For most cancer treatment, about 5–15% of patients get mucositis. However, with 5-fluorouracil (5-FU), up to 40% get mucositis, and 10–15% get grade 3–4 oral mucositis. Irinotecan is associated with severe GI mucositis in over 20% of patients. Seventy-five to eighty percent of bone marrow transplantation recipients experience mucositis, of which oral mucositis is the most common and most debilitating, especially when melphalan is used. In grade 3 oral mucositis, the patient is unable to eat solid food, and in grade 4, the patient is unable to consume liquids as well.

Radiotherapy to the head and neck or to the pelvis or abdomen is associated with Grade 3 and Grade 4 oral or GI mucositis, respectively, often exceeding 50% of patients. Among patients undergoing head and neck radiotherapy, pain and decreased oral function may persist long after the conclusion of therapy. Fractionated radiation dosage increases the risk of mucositis to > 70% of patients in most trials. Oral mucositis is particularly profound and prolonged among HSCT recipients who receive total-body irradiation.

Odynophagia may have environmental or behavioral causes, such as:

- Very hot or cold food and drinks

- Taking certain medications

- Using drugs, tobacco, or alcohol

- Trauma or injury to the mouth, throat, or tongue

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.

A great many diseases involve the mouth, jaws and orofacial skin. Some example pathologies which can involve the oral and maxillofacial region are listed. Some are more common than others, and this list is by no means complete. The examples are considered according to a surgical sieve.

Angular cheilitis (AC), is inflammation of one or both corners of the mouth. Often the corners are red with skin breakdown and crusting. It can also be itchy or painful. The condition can last for days to years. Angular cheilitis is a type of cheilitis (inflammation of the lips).

Angular cheilitis can be caused by infection, irritation, or allergies. Infections include by fungi such as "Candida albicans" and bacteria such as "Staph. aureus". Irritants include poorly fitting dentures, licking the lips or drooling, mouth breathing resulting in a dry mouth, sun exposure, overclosure of the mouth, smoking, and minor trauma. Allergies may include to substances like toothpaste, makeup, and food. Often a number of factors are involved. Other factors may include poor nutrition or poor immune function. Diagnosis may be helped by testing for infections and patch testing for allergies.

Treatment for angular cheilitis is typically based on the underlying causes along with the use of a barrier cream. Frequently an antifungal and antibacterial cream is also tried. Angular cheilitis is a fairly common problem, with estimates that it affects 0.7% of the population. It occurs most often in the 30s to 60s, although is also relatively common in children. In the developing world, iron and vitamin deficiencies are a common cause.

AC almost always affects the lower lip and only rarely the upper lip, probably because the lower lip is more exposed to the sun. In the unusual cases reported where it affects the upper lip, this may be due to upper lip prominence. The commissures (corners of the mouth) are not usually involved.

Affected individuals may experience symptoms such as a dry sensation and cracking of the lips.

It is usually painless and persistent.

The appearance is variable. White lesions indicate hyperkeratosis. Red, erosiive or ulcerative lesions indicate atrophy, loss of epithelium and inflammation. Early, acute lesions may be erythematous (red) and edematous (swollen). With months and years of sun exposure, the lesion becomes chronic and may be grey-white in color and appear dry, scaly and wrinkled.

There is thickening whitish discoloration of the lip at the border of the lip and skin. There is also a loss of the usually sharp border between the red of the lip and the normal skin, known as the vermillion border. The lip may become scaly and indurated as AC progresses.

When palpated, the lip may have a texture similar to rubbing the gloved finger along sandpaper.

AC may occur with skin lesions of actinic keratosis or skin cancer elsewhere, particularly on the head and neck since these are the most sun exposed areas. Rarely it may represent a genetic susceptibility to light damage (e.g. xeroderma pigmentosum or actinic prurigo).

Geographic tongue could be considered to be a type of glossitis. It usually presents only on the dorsal 2/3 and lateral surfaces of the tongue, but less commonly an identical condition can occur on other mucosal sites in the mouth, such as the ventral surface (undersurface) of the tongue, mucosa of the cheeks or lips, soft palate or floor of mouth; usually in addition to tongue involvement. In such cases, terms such as stomatitis erythema migrans, ectopic geographic tongue, areata migrans, geographic stomatitis, or migratory stomatitis are used instead of geographic tongue. Beside the differences in locations of presentation inside the oral cavity and prevalence among the general population, in all other aspects of clinical significance, symptoms, treatment, and histopathologic appearance, these two forms are identical.

This condition is sometimes termed (oral) erythema migrans, but this has no relation to the more common use of the term erythema migrans (erythema chronicum migrans), to describe the appearance of skin lesions in Lyme disease.

Signs and symptoms are dependent upon the type of oral candidiasis. Often, apart from the appearance of the lesions, there are usually no other signs or symptoms. Most types of oral candidiasis are painless, but a burning sensation may occur in some cases. Candidiasis can therefore sometimes be misdiagnosed as burning mouth syndrome. A burning sensation is more likely with erythematous (atrophic) candidiasis, whilst hyperplastic candidiasis is normally entirely asymptomatic. Acute atrophic candidiasis may feel like the mouth has been scalded with a hot liquid. Another potential symptom is a metallic, acidic, salty or bitter taste in the mouth. The pseudomembranous type rarely causes any symptoms apart from possibly some discomfort or bad taste due to the presence of the membranes. Sometimes the patient describes the raised pseudomembranes as "blisters." Occasionally there can be dysphagia (difficulty swallowing), which indicates that the candidiasis involves the oropharynx or the esophagus, as well as the mouth. The trachea and the larynx may also be involved where there is oral candidiasis, and this may cause hoarseness of the voice.

Erythematous (atrophic) candidiasis is when the condition appears as a red, raw-looking lesion. Some sources consider denture-related stomatitis, angular stomatitis, median rhombiod glossitis, and antiobiotic-induced stomatitis as subtypes of erythematous candidiasis, since these lesions are commonly erythematous/atrophic. It may precede the formation of a pseudomembrane, be left when the membrane is removed, or arise without prior pseudomembranes. Some sources state that erythematous candidiasis accounts for 60% of oral candidiasis cases. Where it is associated with inhalation steroids (often used for treatment of asthma), erythematous candidiasis commonly appears on the palate or the dorsum of the tongue. On the tongue, there is loss of the lingual papillae (depapillation), leaving a smooth area.

Acute erythematous candidiasis usually occurs on the dorsum of the tongue in persons taking long term corticosteroids or antibiotics, but occasionally it can occur after only a few days of using a topical antibiotic. This is usually termed "antibiotic sore mouth", "antibiotic sore tongue", or "antibiotic-induced stomatitis" because it is commonly painful as well as red.

Chronic erythematous candidiasis is more usually associated with denture wearing (see denture-related stomatitis).