Some cases of pharyngitis are caused by fungal infection such as Candida albicans causing oral thrush.

Pharyngitis may also be caused by mechanical, chemical or thermal irritation, for example cold air or acid reflux. Some medications may produce pharyngitis such as pramipexole and antipsychotics.

Laryngitis that continues for more than three weeks is considered chronic. If laryngeal symptoms last for more than three weeks, a referral should be made for further examination, including direct laryngoscopy. The prognosis for chronic laryngitis varies depending on the cause of the laryngitis.

It has been hypothesized that biofilm bacterial infections may account for many cases of antibiotic-refractory chronic sinusitis. Biofilms are complex aggregates of extracellular matrix and inter-dependent microorganisms from multiple species, many of which may be difficult or impossible to isolate using standard clinical laboratory techniques. Bacteria found in biofilms have their antibiotic resistance increased up to 1000 times when compared to free-living bacteria of the same species. A recent study found that biofilms were present on the mucosa of 75% of people undergoing surgery for chronic sinusitis.

Acute sinusitis is usually precipitated by an earlier upper respiratory tract infection, generally of viral origin, mostly caused by rhinoviruses, coronaviruses, and influenza viruses, others caused by adenoviruses, human parainfluenza viruses, human respiratory syncytial virus, enteroviruses other than rhinoviruses, and metapneumovirus. If the infection is of bacterial origin, the most common three causative agents are "Streptococcus pneumoniae", "Haemophilus influenzae", and "Moraxella catarrhalis". Until recently, "Haemophilus influenzae" was the most common bacterial agent to cause sinus infections. However, introduction of the "H. influenza" type B (Hib) vaccine has dramatically decreased "H. influenza" type B infections and now non-typable "H. influenza" (NTHI) are predominantly seen in clinics. Other sinusitis-causing bacterial pathogens include "Staphylococcus aureus" and other streptococci species, anaerobic bacteria and, less commonly, gram negative bacteria. Viral sinusitis typically lasts for 7 to 10 days, whereas bacterial sinusitis is more persistent. Approximately 0.5% to 2% of viral sinusitis results in subsequent bacterial sinusitis. It is thought that nasal irritation from nose blowing leads to the secondary bacterial infection.

Acute episodes of sinusitis can also result from fungal invasion. These infections are typically seen in patients with diabetes or other immune deficiencies (such as AIDS or transplant patients on immunosuppressive anti-rejection medications) and can be life-threatening. In type I diabetics, ketoacidosis can be associated with sinusitis due to mucormycosis.

Chemical irritation can also trigger sinusitis, commonly from cigarette smoke and chlorine fumes. Rarely, it may be caused by a tooth infection.

Acute laryngitis may persist, but will typically resolve on its own within two weeks. Recovery is likely to be quick if the patient follows the treatment plan. In viral laryngitis, symptoms can persist for an extended amount of time, even when upper respiratory tract inflammation has been resolved.

There is low or very-low quality evidence that probiotics may be better than placebo in preventing acute URTIs. Vaccination against influenza viruses, adenoviruses, measles, rubella, "Streptococcus pneumoniae", "Haemophilus influenzae", diphtheria, "Bacillus anthracis", and "Bordetella pertussis" may prevent them from infecting the URT or reduce the severity of the infection.

In terms of pathophysiology, rhino virus infection resembles the immune response. The viruses do not cause damage to the cells of the upper respiratory tract but rather cause changes in the tight junctions of epithelial cells. This allows the virus to gain access to tissues under the epithelial cells and initiate the innate and adaptive immune responses.

Up to 15% of acute pharyngitis cases may be caused by bacteria, most commonly "Streptococcus pyogenes", a group A streptococcus in streptococcal pharyngitis ("strep throat"). Other bacterial causes are "Streptococcus pneumoniae", "Haemophilus influenzae", "Corynebacterium diphtheriae", "Bordetella pertussis", and "Bacillus anthracis".

Sexually transmitted infections have emerged as causes of oral and pharyngeal infections.

In chronic recurrent sialadenitis or chronic sclerosing sialadenitis, acute attacks are managed with conservative therapies such as hydration, analgesics (mainly NSAIDs), sialogogues to stimulate salivary secretion, and regular, gentle gland massage. If infection is present, appropriate cultures should be obtained, followed by empirical antibiotic therapy initially, for example amoxicillin/clavulanate or clindamycin which cover oral flora.

If there are attacks more than approximately 3 times per year or severe attacks, surgical excision of the affected gland should be considered.

Sialadenitis (sialoadenitis) is inflammation of a salivary gland. It may be subdivided temporally into acute, chronic and recurrent forms.

Nasal vestibulitis is the diffuse dermatitis of nasal vestibule. It is often caused by "Staphylococcus aureus." It may be secondary to chronic rhinorrhea, nose picking or viral infections. In acute vestibulitis, the skin is red, swollen and tender. In chronic vestibulitis, induration of vestibular skin and crusting is seen. It is treated by cleaning the nasal vestibule of all crusts with a cotton applicator soaked in hydrogen peroxide. Antibiotic steroid ointment is sometimes helpful. Chronic fissures are treated by cautery.

Due to the human ear's function of regulating the pressure within the head region, catarrh blockage may cause discomfort during changes in atmospheric pressure.

Catarrh , or catarrhal inflammation, is inflammation of the mucous membranes in one of the airways or cavities of the body, usually with reference to the throat and paranasal sinuses. It can result in a thick exudate of mucus and white blood cells caused by the swelling of the mucous membranes in the head in response to an infection. It is a symptom usually associated with the common cold, pharyngitis, and chesty coughs, but it can also be found in patients with adenoiditis, otitis media, sinusitis or tonsillitis. The phlegm produced by catarrh may either discharge or cause a blockage that may become chronic.

The word "catarrh" was widely used in medicine since before the era of medical science, which explains why it has various senses and in older texts may be synonymous with, or vaguely indistinguishable from, common cold, nasopharyngitis, pharyngitis, rhinitis, or sinusitis. The word is no longer as widely used in American medical practice, mostly because more precise words are available for any particular pathosis. Indeed, to the extent that it is still used, it is no longer viewed nosologically as a disease entity but instead as a symptom, a sign, or a syndrome of both. The term "catarrh" is found in medical sources from the United Kingdom. The word has also been common in the folk medicine of Appalachia, where medicinal plants have been used to treat the inflammation and drainage associated with the condition.

Chronic bacterial prostatitis is a bacterial infection of the prostate gland. It should be distinguished from other forms of prostatitis such as acute bacterial prostatitis and chronic pelvic pain syndrome (CPPS).

Chronic bacterial prostatitis is a relatively rare condition that usually presents with an intermittent UTI-type picture. It is defined as recurrent urinary tract infections in men originating from a chronic infection in the prostate. Symptoms may be completely absent until there is also bladder infection, and the most troublesome problem is usually recurrent cystitis.

Chronic bacterial prostatitis occurs in less than 5% of patients with prostate-related non-BPH lower urinary tract symptoms (LUTS).

Dr. Weidner, Professor of Medicine, Department of Urology, University of Gießen, has stated: "In studies of 656 men, we seldom found chronic bacterial prostatitis. It is truly a rare disease. Most of those were E-coli."

Chronic bronchitis has a 3.4% to 22% prevalence rate among the general population. Individuals over the age of 45, smokers, those that live in areas with high air pollution and those have asthma have a higher risk of developing chronic bronchitis. This wide range is due to the different definitions of chronic bronchitis which can be defined based on signs and symptoms or the clinical diagnosis of the disorder. Chronic bronchitis tends to affect men more often than women. While the primary risk factor for chronic bronchitis is smoking, there is still a 4%-22% chance that people with chronic bronchitis were never smokers. This might suggest other risk factors such as the inhalation of fuels, dusts, and fumes. Obesity has also been linked to an increased risk in the onset of chronic bronchitis. In the United States in the year 2014 per 100,000 population the death rate of chronic bronchitis was 0.2%.

Acute bronchitis is one of the most common diseases. About 5% of adults are affected and about 6% of children have at least one episode a year. It occurs more often in the winter. More than 10 million people in the United States visit a doctor each year for this condition with about 70% receiving antibiotics which are mostly not needed. There are efforts to decrease the use of antibiotics in acute bronchitis.

Chronic mucocutaneous candidiasis can be diagnosed in an affected individual via the following methods/tests:

In terms of the cause of chronic mucocutaneous candidiasis one finds it can be inherited either autosomal dominant or autosomal recessive There are 9 types of this condition with the first CANDF1 being located at 2p22.3-p21(cytogenetically)

Chronic mediastinitis is usually a radiologic diagnosis manifested by diffuse fibrosis of the soft tissues of the mediastinum. This is sometimes the consequence of prior granulomatous disease, most commonly histoplasmosis. Other identifiable causes include tuberculosis, IgG4-related disease and radiation therapy. Fibrosing mediastinitis most frequently causes problems by constricting blood vessels or airways in the mediastinum. This may result in such complications as superior vena cava syndrome or pulmonary edema from compression of pulmonary veins.

Treatment for chronic fibrosing mediastinitis is somewhat controversial, and may include steroids or surgical decompression of affected vessels.

Before the development of modern cardiovascular surgery, cases of acute mediastinitis usually arose from either perforation of the esophagus or from contiguous spread of odontogenic or retropharyngeal infections. However, in modern practice, most cases of acute mediastinitis result from complications of cardiovascular or endoscopic surgical procedures.

Treatment usually involves aggressive intravenous antibiotic therapy and hydration. If discrete fluid collections or grossly infected tissue have formed (such as abscesses), they may have to be surgically drained or debrided.

In recent years the prognosis for CP/CPPS has improved with the advent of multimodal treatment, phytotherapy, protocols aimed at quieting the pelvic nerves through myofascial trigger point release and anxiety control, and chronic pain therapy.

The annual prevalence in the general population of chronic pelvic pain syndrome is 0.5%. 38% of primary care providers, when presented with a vignette of a man with CPPS, indicate that they have never seen such a patient. However, the overall prevalence of symptoms suggestive of CP/CPPS is 6.3%. The role of the prostate was questioned in the cause of CP/CPPS when both men and women in the general population were tested using the (1) National Institutes of Health Chronic Prostatitis Symptom Index (NIH-CPSI) —with the female homolog of each male anatomical term use on questionnaires for female participants— (2) the International Prostate Symptom Score (IPSS), and (3) additional questions on pelvic pain. The prevalence of symptoms suggestive of CPPS in this selected population was 5.7% in women and 2.7% in men, placing in doubt the role of the prostate gland. New evidence suggests that the prevalence of CP/CPPS is much higher in teenage males than once suspected.

Little is known about the cause of vestibulodynia. A number of causes may be involved, including sub-clinical human papillomavirus infection, chronic recurrent candidiasis, or chronic recurrent bacterial vaginosis. Muscular causes have been implicated as well, since chronic vulvar pain may be the result of chronic hypertonic perivaginal muscles, leading to vaginal tightening and subsequent pain. Some investigators have postulated the existence of neurological causes, such as vestibular neural hyperplasia. Finally, psychological factors may contribute to or exacerbate the problem, since the anticipation of pain often results in a conditioned spasmodic reflex along with sexual desire and arousal problems.

Chronic gastritis is a chronic inflammation of the gastric mucosa.