In 80% of cases, the parotid gland is affected. Lacrimal glands are also affected.

Infections involving the salivary glands can be viral or bacterial (or rarely fungal).

- Mumps is the most common viral sialadenitis. It usually occurs in children, and there is preauricular pain (pain felt in front of the ear), swelling of the parotid, fever, chills, and headaches.

- Bacterial sialadentitis is usually caused by ascending organisms from the oral cavity. Risk factors include reduced salivary flow rate.

- Human immunodeficiency virus-associated salivary gland disease (HIV-SGD).

Most patients will fully recover from dacryoadenitis. For conditions with more serious causes, such as sarcoidosis, the prognosis is that of the underlying condition.

Ectopic salivary gland tissue which is located in sites other than the normal location is variously described as aberrant, accessory, ectopic, heterotopic or salivary gland choristoma.

Standard, and most effective, therapy to date is glandular sialadenectomy, which is associated with fairly low operative morbidity; however, in recent times, the administration of steroid (which can shrink the inflammatory lesion and is known to reduce serum IgG4 values) has been considered favorably, and may be useful in younger patients or those who refuse surgery.

A salivary diverticulum (plural "diverticuli") is a small pouch or out-pocketing of the duct system of a major salivary gland. Such diverticuli typically cause pooling of saliva and recurrent sialadenitis, especially parotitis. A diverticulum may also cause a sialolith to form.

The condition can be diagnosed by sialography. Affected individuals may "milk" the salivary gland to encourage flow of saliva through the duct.

Benign lymphoepithelial lesion is most likely to occur in adults around 50 years of age. There is a predilection for gender with 60–80% being female. The gland affected has a diffuse swelling. The swelling can be asymptomatic, but mild pain can also be associated. There is a preponderance of this disease in those who suffer from HIV infection.

Most cases of benign lymphoepithelial lesions appear in conjunction with Sjögren's syndrome. When Sjögren's syndrome is present, the swelling is usually bilateral. Otherwise, the affected glands are usually only on one side of the body.

In many cases, a biopsy is needed to distinguish benign lymphoepithelial lesions from sialadenosis (sialosis).

"Dehydration:"

This is a common, non-infectious cause of parotitis. It may occur in elderly or after surgery.

These are also collectively known as chronic punctate parotitis or chronic autoimmune parotitis.

"Sjögren's syndrome:"

Chronic inflammation of the salivary glands may also be an autoimmune disease known as Sjögren's syndrome. The disease most commonly appears in people aged 40–60 years, but it may affect small children. In Sjögren syndrome, the prevalence of parotitis in women versus men is approximately 9:1. The involved parotid gland is enlarged and tender at times. The cause is unknown. The syndrome is often characterized by excessive dryness in the eyes, mouth, nose, vagina, and skin.

"Lymphoepithelial lesion of Godwin:"

Most frequently associated with a circumscribed tumor with the histologic features of Sjögren syndrome. This designation has also fallen out of favour.

Mumps can be prevented by immunization. Gonococcus, bacteria can be avoided by the use of condoms. Most other causes cannot be prevented.

The cause and pathogenesis of this chronic condition are not very well understood. Several factors have been postulated:

- Formation of a hard salivary calculus or sialolith by accumulation of calcium salts in the duct of the salivary gland (a process known as Sialolithiasis). This has been proposed as the most common cause for Küttner's tumor of the submandibular gland, with sialoliths observed in an appreciable proportion of cases. However, sialolith involvement may not be found in many cases.

- Abnormalities of the salivary gland ducts leading to excessive accumulation or retention of ductal secretions, which can excite chronic inflammations.

- Immune, especially autoimmune, cause - which has gained steam, given the observation that the tissue of the glands is overrun with lymphoid immune cells and fibrous connective tissue, as well as corroboration from markedly similar lesions (with histologic and immunohistochemical findings) seen elsewhere in the body. The presence of abundant Immunoglobulin G4 (IgG4) associated with Plasma cells infiltrating into the salivary glands, as well as increased serum IgG4 concentration, has been noted with patients with Küttner's tumor.

This chronic condition is primarily observed in adult (40–70 years) patients. However, Küttner's tumor, with prominent immunopathological features, has been described in an 11-year-old boy in Brazil in 2012.

An "accessory salivary gland" is ectopic salivary gland tissue with a salivary gland duct system. The most common location of accessory salivary gland tissue is an extra major salivary gland in front of the parotid gland. It is typically about 3 cm or less in size, and drains into the parotid duct via a single tributary. Accessory parotid tissue is found in 21-56% of adults. Any disease process which affects the salivary glands, including cancer, may also occur within an accessory salivary gland tissue.

This is a rare condition, probably caused by an allergic reaction, in which there is sudden swelling of the salivary glands. It is associated with other allergic conditions such as asthma, urticaria, allergic rhinitis and food allergy.

The prevalence of salivary stones in the general population is about 1.2% according to post mortem studies, but the prevalence of salivary stones which cause symptoms is about 0.45% in the general population. Sialolithiasis accounts for about 50% of all disease occurring in major salivary glands, and for about 66% of all obstructive salivary gland diseases. Salivary gland stones are twice as common in males as in females. The most common age range in which they occur is between 30 and 60, and they are uncommon in children.

Sialodochitis (also termed ductal sialadenitis), is inflammation of the duct system of a salivary gland. This is compared to sialadenitis, which is inflammation of the gland parenchyma.

Sialodochitis may be associated with salivary duct strictures and salivary stones.

It is common in both the parotid glands and submandibular glands.

The treatment is as for sialadenitis.

Causes can be remembered by mnemonic HERNIA:

- Hereditary factors: the disease runs in families

- Endocrine imbalance: the disease tends to start at puberty and mostly involves females

- Racial factors: whites are more susceptible than natives of equatorial Africa

- Nutritional deficiency: vitamins A or D, or iron

- Infection: "Klebsiella ozaenae", diphtheroids, "Proteus vulgaris", "E. coli", etc.

- Autoimmune factors: viral infection or some other unidentified insult may trigger antigenicity of the nasal mucosa.

The condition is rare. It is more likely to occur in persons who regularly have raised pressure in the mouth, for example wind instrument players, and balloon and glass-blowers. Cases have also been reported with bicycle tyre inflation, whistling, nose blowing, cough and valsalva manoeuvre to clear the ears. It can be an iatrogenic effect of dental treatment, spirometry, and positive pressure ventilation. Apart from these factors, the condition mainly occurs in adolescents, often self-inflicted due to psychological issues.

Specific infections, such as syphilis, lupus, leprosy and rhinoscleroma, may cause destruction of the nasal structures leading to atrophic changes. Atrophic rhinitis can also result from long-standing purulent sinusitis or radiotherapy of the nose, or as a complication of surgery of the turbinates. The United Kingdom National Health Service has stated that "Most cases of atrophic rhinitis in the UK occur when the turbinates are damaged or removed during surgery". Some authors refer to as Atrophic rhinitis secondary to sinus surgery as the empty nose syndrome.

They generally have a good prognosis. In one larger study, the 5-year and 10-year survival were over 90% and 80% respectively.

80% of patients with pituitary antibodies also have antibodies to thyroid gland or its hormones. Likewise, 20% of autoimmune thyroid patients also have pituitary antibodies. It follows that a subset of thyroid patients may have a disease related to autoimmune hypophysitis. Recent research has focused on a defect at the CTLA-4 gene which, coupled with other factors, may result in autoimmunity primarily focusing on certain endocrine glands including the pituitary and thyroid.

Little is known about the total incidence of salivary gland tumours as most benign tumours go unrecorded in national cancer registries. The majority of salivary tumours are benign (65-70%). Within the parotid gland 75 - 80% of tumours are benign. Around 50% of the tumours found in the submandibular glands are benign. Sublingual gland tumours are very rare but if present, they are most likely to be malignant.

In the United States, salivary gland cancers are uncommon with an incidence rate of 1.7 in 100000 between 2009 and 2013.

The symptoms depend on what part of the pituitary is affected. Lymphocytic adenohypophysitis (LAH) occurs when the anterior pituitary cells are affected by autoimmune inflammation resulting in either no symptoms, adrenal insufficiency (if the ACTH producing cells are affected), hypothyroidism (if the TSH producing cells are damaged), or hypogonadism (if the LH and/or FSH producing cells are involved). In some cases, the presence of inflammation within the pituitary gland leads to interruption of dopamine flow from the hypothalamus into the pituitary causing high levels of the hormone prolactin and, often as a consequence, milk production from the breasts (in older girls and women). Lymphocytic Infundibuloneurohypophysitis (LINH) occurs when the posterior pituitary is affected resulting in diabetes insipidus. Both LAH and LINH may also lead to symptoms of an intracranial mass such as headache or disturbance of vision, i.e. bitemporal hemianopia.

The pituitary produces multiple hormones relating to various metabolic functions. Sufficiently low production of certain pituitary hormones can be fatal resulting in the failure of the thyroid or adrenal glands.

It is estimated that, typically, it takes from 12 to 40 years for autoimmune destruction to present symptoms. However, there have been cases of isolated attacks as a result of drug reactions (i.e., use of blocking antibody ipilimumab) or idiopathic events that have presented symptoms which may disappear after relatively short term treatment (i.e., 1 year on corticoids or other immune suppressants). However, more rapid development of the disorder is the rule when it occurs during, or shortly after, pregnancy (even after miscarriage or abortion). Indeed, autoimmune hypophysitis occurs more commonly during and shortly after pregnancy than at any other time.

Hyperthyroidism is a state in which the body is producing too much thyroid hormone. The main hyperthyroid conditions are:

- Graves' disease

- Toxic thyroid nodule

- Thyroid storm

- Toxic nodular struma (Plummer's disease)

- Hashitoxicosis: "transient" hyperthyroidism that can occur in Hashimoto's thyroiditis

Most types of thyroiditis are three to five times more likely to be found in women than in men. The average age of onset is between thirty and fifty years of age. This disease tends to be geographical and seasonal, and is most common in summer and fall.

Recurrent pneumoparotitis may predispose to sialectasis, recurrent parotitis, and subcutaneous emphysema of the face and neck, and mediastinum, and potentially pneumothorax.