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). Burning mouth syndrome – 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.
Radiation therapy
Radiation therapy for cancers of the head and neck (including brachytherapy for thyroid cancers) where the salivary glands are close to or within the field irradiated is another major cause of xerostomia. A radiation dose of 52 Gy is sufficient to cause severe salivary dysfunction. Radiotherapy for oral cancers usually involves up to 70 Gy of radiation, often given along with chemotherapy which may also have a damaging effect on saliva production. This side effect is a result of radiation damage of the parasympathetic nerves. Formation of salivary gland ducts depends on the secretion of a neuropeptide from the parasympathetic nerves, while development of the end buds of the salivary gland depends on acetylcholine from the parasympathetic nerves. Sicca syndrome
"Sicca" simply means dryness. Sicca syndrome is not a specific condition, and there are varying definitions, but the term can describe oral and eye dryness that is not caused by autoimmune diseases (e.g., Sjögren syndrome). Other causes
Oral dryness may also be caused by mouth breathing, usually caused by partial obstruction of the upper respiratory tract. Examples include hemorrhage, vomiting, diarrhea, and fever.Alcohol may be involved in the cause of salivary gland disease, liver disease, or dehydration.Smoking is another possible cause. Other recreational drugs such as methamphetamine, cannabis, hallucinogens, or heroin, may be implicated. Hormonal disorders, such as poorly controlled diabetes, chronic graft versus host disease or low fluid intake in people undergoing hemodialysis for renal impairment may also result in xerostomia, due to dehydration.Nerve damage can be a cause of oral dryness.