Rhinorrhea can also occur when individuals with allergies to certain substances, such as pollen, dust, latex, soy, shellfish, or animal dander, are exposed to these allergens. In people with sensitized immune systems, the inhalation of one of these substances triggers the production of the antibody immunoglobulin E (IgE), which binds to mast cells and basophils. IgE bound to mast cells are stimulated by pollen and dust, causing the release of inflammatory mediators such as histamine. In turn, this causes, among other things, inflammation and swelling of the tissue of the nasal cavities as well as increased mucus production. Particulate matter in polluted air and chemicals such as chlorine and detergents, which can normally be tolerated, can make the condition considerably worse.

Rhinorrhea can be a symptom of other diseases, such as the common cold or influenza. During these infections, the nasal mucous membranes produce excess mucus, filling the nasal cavities. This is to prevent infection from spreading to the lungs and respiratory tract, where it could cause far worse damage. It has also been suggested that rhinorrhea is a result of viral evolution, and may be a response that is not useful to the host, but which has evolved by the virus to maximise its own infectivity. Rhinorrhea caused by these infections usually occur on circadian rhythms. Over the course of a viral infection, sinusitis (the inflammation of the nasal tissue) may occur, causing the mucous membranes to release more mucus. Acute sinusitis consists of the nasal passages swelling during a viral infection. Chronic sinusitis occurs when one or more nasal polyps appear. This can be caused by a deviated septum as well as a viral infection.

Common issues that lead to overuse of topical decongestants:

- Deviated septum

- Upper respiratory tract infection

- Vasomotor rhinitis

- Cocaine use and other stimulant abuse

- Pregnancy (these products are not considered safe for pregnancy)

- Chronic rhinosinusitis

- Hypertrophy of the inferior turbinates

It is inflammation of the voice box which can occur from overuse, irritation or an infection. Laryngitis can be a short term illness or a prolonged problem. The majority of cases of laryngitis are due to viral infections which only last a few days. Laryngitis is often a common complaint in individuals who sing. Opera singers or those who yell at sporting events strain the throat muscles and develop a case of laryngitis. However, persistent throat irritation and hoarseness may be from a more serious disorder like cancer.

Viruses are common causes of the common cold. Less often, bacteria may also cause pharyngitis. Both of these organisms enter the body via the nose or mouth as aerosolized particles when someone sneezes or coughs. Because many germs are contagious, one can even acquire them from touching utensils, toys, personal care products or door knobs. The most common viruses that causes throat irritation include the common cold virus, influenza, infectious mononucleosis, measles and croup. Most bacteria and viruses usually induce throat irritation during the winter or autumn.

One of the most common areas of the body associated with irritation is the vagina. Many women complain of an itch, dryness, or discharge in the perineum at some point in their lives. There are several causes of vaginal irritation including fungal vaginitis (like candida) or trichomoniasis. Often, herpes simplex infection of the mouth or genitalia can be recurrent and prove to be extremely irritating.

Sometimes, the irritation can be of the chronic type and it can be so intense that it also causes painful intercourse. Aside from infections, chronic irritation of the vagina may be related to the use of contraceptives and condoms made from latex. The majority of contraceptives are made of synthetic chemicals which can induce allergies, rash and itching. Sometimes the lubricant used for intercourse may cause irritation.

Another cause of irritation in women is post menopausal vaginitis. The decline in the female sex hormones leads to development of dryness and itching in the vagina. This is often accompanied by painful sexual intercourse. Cracks and tears often develop on outer aspects of the labia which becomes red from chronic scratching. Post menopausal vaginitis can be treated with short term use of vaginal estrogen pessary and use of a moisturizer.

Individuals who smoke or are exposed to smog or other airborne pollutants can develop a condition known as COPD. In this disorder, there is constant irritation of the breathing tubes (trachea) and the small airways. The constant irritation results in excess production of mucus which makes breathing difficult. Frequently, these individuals wake up in the morning with copious amounts of foul smelling mucus and a cough which lasts all day. Wheeze and heavy phlegm are common findings. COPD is a lifelong disorder and there is no cure. Eventually most people develop recurrent pneumonia, lack any type of endurance, and are unable to work productively. One of the ways to avoid chronic bronchitis is to stop or not smoke.

The characteristic presentation of RM involves nasal congestion without rhinorrhea, postnasal drip, or sneezing following several days of decongestant use. This condition typically occurs after 5–7 days of use of topical decongestants. Patients often try increasing both the dose and the frequency of nasal sprays upon the onset of RM, worsening the condition. The swelling of the nasal passages caused by rebound congestion may eventually result in permanent turbinate hyperplasia, which may block nasal breathing until surgically removed.

The treatment of nasal congestion frequently depends on the underlying cause.

Alpha-adrenergic agonists are the first treatment of choice. They relieve congestion by constricting the blood vessels in the nasal cavity, thus resulting in relieved symptoms. Examples include oxymetazoline and phenylephrine.

Both influenza and the common cold are self-limiting conditions that improve with time; however, drugs such as acetaminophen (paracetamol), aspirin, and ibuprofen may help with the discomfort.

A cause of nasal congestion may also be due to an allergic reaction caused by hay fever, so avoiding allergens is a common remedy if this becomes a confirmed diagnosis. Antihistamines and decongestants can provide significant symptom relief although they do not cure hay fever. Antihistamines may be given continuously during pollen season for optimum control of symptoms. Topical decongestants should only be used by patients for a maximum of 3 days in a row, because rebound congestion may occur in the form of rhinitis medicamentosa.

Nasal decongestants target discomfort directly. These come as nasal sprays like naphazoline (Privine), oxymetazoline (Afrin, Dristan, Duramist), as inhalers, or phenylephrine (Neo-Synephrine, Sinex, Rhinall) or as oral pills (Bronkaid, Sudafed, Neo-Synephrine, Sinex, Rhinall). Oral decongestants may be used for up to a week without consulting a doctor, with the exception of Bronkaid and Sudafed, which can be taken as long as needed, but nasal sprays can also cause "rebound" (Rhinitis medicamentosa) and worsen the congestion if taken for more than a few days. Therefore, you should only take nasal sprays when discomfort cannot be remedied by other methods, and never for more than three days.

If an infant is unable to breathe because of a plugged nose, a nasal aspirator may be useful to remove the mucus. The mucus might be thick and sticky, making it difficult to expel from the nostril.

Nasal congestion is the blockage of the nasal passages usually due to membranes lining the nose becoming swollen from inflamed blood vessels.

Nasal decongestants target the discomfort directly. These come as nasal sprays, inhalers, and as oral pills.

Nasal congestion has many causes and can range from a mild annoyance to a life-threatening condition. Most people prefer to breathe through the nose (historically referred to as "obligate nasal breathers"). Nasal congestion in an infant in the first few months of life can interfere with breastfeeding and cause life-threatening respiratory distress; in older children and adolescents it is often just an annoyance but can cause other difficulties.

Nasal congestion can interfere with the hearing and speech. Significant congestion may interfere with sleep, cause snoring, and can be associated with sleep apnea. In children, nasal congestion from enlarged adenoids has caused chronic sleep apnea with insufficient oxygen levels and hypoxia, as well as right-sided heart failure. The problem usually resolves after surgery to remove the adenoids and tonsils, however the problem often relapses later in life due to craniofacial alterations from chronic nasal congestion.

Nasal congestion can also cause mild facial and head pain, and a degree of discomfort, often from allergies or the common cold.

Nasal mucosa has rich blood supply and has venous sinusoids or "lakes" surrounded by smooth muscle fibers. These smooth muscle fibers act as sphincters and control the filling and emptying of sinusoids. Sympathetic stimulation causes vasoconstriction and shrinkage of mucosa, which leads to decongestion of nose. Parasympathetic stimulation causes not only excessive secretion from the nasal gland but also vasodilatation and engorgement, which lead to rhinorrhoea and congestion of nose. The autonomic nervous system, which supplies the nasal mucosa, is under the control of the hypothalamus. Therefore, emotions play significant role in nonallergic rhinitis.

Nonallergic rhinitis is inflammation of the inner part of the nose that is not caused by an allergy. Nonallergic rhinitis involves symptoms including chronic sneezing or having a congested, drippy nose without an identified allergic reaction. Other common terms for nonallergic rhinitis are vasomotor rhinitis and perennial rhinitis. The prevalence of nonallergic rhinitis in otolaryngology is 40%. Allergic rhinitis is more common than nonallergic rhinitis; however, both conditions have similar presentation, manifestation and treatment. Nasal itching and paroxysmal sneezing are usually associated with nonallergic rhinitis in comparison to allergic rhinitis.

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.

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.

Empty nose syndrome has been observed to affect a small proportion of people who have undergone surgery to the nose or sinuses, particularly those who have undergone turbinectomy (a procedure that removes some of the bones in the nasal passage). The incidence of ENS is variable and has not yet been quantified, but it is considered rare.

Untreated, the condition can cause significant and longterm physical and emotional distress in some people; some of the initial presentations on the condition described people who committed suicide. It is difficult to determine what treatments are safe and effective, and to what extent, in part because the diagnosis itself is unclear.

First-generation antihistamine has been suggested as first-line therapy to treat post-nasal drip.

Rhinitis medicamentosa is a form of drug-induced nonallergic rhinitis which is associated with nasal congestion brought on by the use of certain oral medications (primarily sympathomimetic amine and 2-imidazoline derivatives) and topical decongestants (e.g., oxymetazoline, phenylephrine, xylometazoline, and naphazoline nasal sprays) that constrict the blood vessels in the lining of the nose.

Perhaps the most universal risk of sneezing is the spread of disease. Bacterial infections can spread to susceptible uninfected people via the spread of microscopic organisms suspended in the droplets expelled by a sneeze. Bacteria which commonly spread by sneezing include bacterial meningitis, strep throat, and tuberculosis. Viral infections can also be spread by sneezing. When a virus is expelled by a sneeze, its mucous membrane evaporates, and the virus becomes a droplet nucleus which can be inhaled by another person, thus spreading the virulent infection. Examples of virulent infections that spread by sneezing include measles, mumps, rubella, and influenza.

Nonallergic rhinitis refers to rhinitis that is not due to an allergy. The category was formerly referred to as vasomotor rhinitis, as the first cause discovered was vasodilation due to an overactive parasympathetic nerve response. As additional causes were identified, additional types of nonallergic rhinitis were recognized. Vasomotor rhinitis is now included among these under the more general classification of nonallergic rhinitis. The diagnosis is made upon excluding allergic causes. It is an umbrella term of rhinitis of multiple causes, such as occupational (chemical), smoking, gustatory, hormonal, senile (rhinitis of the elderly), atrophic, medication-induced (including rhinitis medicamentosa), local allergic rhinitis, non-allergic rhinitis with eosinophilia syndrome (NARES) and idiopathic (vasomotor or non-allergic, non-infectious perennial allergic rhinitis (NANIPER), or non-infectious non-allergic rhinitis (NINAR).

In vasomotor rhinitis, certain nonspecific stimuli, including changes in environment (temperature, humidity, barometric pressure, or weather), airborne irritants (odors, fumes), dietary factors (spicy food, alcohol), sexual arousal, exercise, and emotional factors trigger rhinitis. There is still much to be learned about this, but it is thought that these non-allergic triggers cause dilation of the blood vessels in the lining of the nose, which results in swelling and drainage.

Non-allergic rhinitis can co-exist with allergic rhinitis, and is referred to as "mixed rhinitis." The pathology of vasomotor rhinitis appears to involve neurogenic inflammation and is as yet not very well understood. Vasomotor rhinitis appears to be significantly more common in women than men, leading some researchers to believe that hormones play a role. In general, age of onset occurs after 20 years of age, in contrast to allergic rhinitis which can be developed at any age. Individuals with vasomotor rhinitis typically experience symptoms year-round, though symptoms may be exacerbated in the spring and autumn when rapid weather changes are more common. An estimated 17 million United States citizens have vasomotor rhinitis.

Drinking alcohol may cause rhinitis as well as worsen asthma (see alcohol-induced respiratory reactions). In certain populations, particularly those of East Asian countries such as Japan, these reactions have a nonallergic basis. In other populations, particularly those of European descent, a genetic variant in the gene that metabolizes ethanol to acetaldehyde, ADH1B, is associated with alcohol-induced rhinitis. It is suggested that this variant metabolizes ethanol to acetaldehyde too quickly for further processing by ALDH2 and thereby leads to the accumulation of acetaldehyde and rhinitis symptoms. In these cases, alcohol-induced rhinitis may be of the "mixed rhinitis" type and, it seems likely, most cases of alcohol-induced rhinitis in non-Asian populations reflect true allergic response to the non-ethanol and/or contaminants in alcoholic beverages, particularly when these beverages are wines or beers. Alcohol-exacerbated rhinitis is more frequent in individuals with a history of rhinitis exacerbated by aspirin.

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), particularly those that inhibit cyclooxygenase 1 (COX1), can worsen rhinitis and asthma symptoms in individuals with a history of either one of these diseases. These exacerbations most often appear due to NSAID hypersensitivity reactions rather than NSAID-induced allergic reactions.

The antihistamine azelastine, applied as a nasal spray, may be effective for vasomotor rhinitis. Fluticasone propionate or budesonide (both are steroids) in nostril spray form may also be used for symptomatic treatment. The antihistamine cyproheptadine is also effective, probably due to its antiserotonergic effects.

A Cochrane review on non-allergic rhinitis reports improvement of overall function after treatment with capsaicin (the active component of chili peppers). The quality of evidence is low, however.

PND is suggested to be a cause of extra-oral halitosis, especially when a sinus infection is also present. Acid reflux or heartburn is believed to aggravate and in some cases cause post-nasal drip. Post-nasal drip can be a cause of laryngeal inflammation and hyperresponsiveness, leading to symptoms of vocal cord dysfunction (VCD).

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.

Sneezing generally does not present any particular risks to the individual, and is usually more of an annoyance than a risk of injury. The fits of sneezing brought about by the photic sneeze reflex can, however, have dangerous implications during certain scenarios and activities, such as operating a vehicle, or while undergoing operations (dental, optical) and having bright lights directed towards the patient's face.

If a specific cause for pruritus ani is found it is classified as "secondary pruritus ani". If a specific cause is NOT found it is classified as "idiopathic pruritus ani". The irritation can be caused by intestinal parasites, anal perspiration, frequent liquid stools, diarrhea, residual stool deposits, or the escape of small amounts of stool as a result of incontinence or flatulence. Another cause is yeast infection or candidiasis. Some diseases increase the possibility of yeast infections, such as diabetes mellitus or HIV infection. Treatment with antibiotics can bring about a disturbance of the natural balance of intestinal flora, and lead to perianal thrush, a yeast infection affecting the anus. Psoriasis also can be present in the anal area and cause irritation. Abnormal passageways (fistulas) from the small intestine or colon to the skin surrounding the anus can form as a result of disease (such as Crohn's disease), acting as channels which may allow leakage of irritating fluids to the anal area. Other problems that can contribute to anal itching include pinworms, hemorrhoids, tears of the anal skin near the mucocutaneous junction (fissures), and skin tags (abnormal local growth of anal skin). Aside from diseases relative to the condition, a common view suggests that the initial cause of the itch may have passed, and that the illness is in fact prolonged by what is known as an itch-scratch-itch cycle. It states that scratching the itch encourages the release of inflammatory chemicals, which worsen redness, intensifies itchiness and increases the area covered by dry skin, thereby causing a snowball effect.

Some authorities describe “psychogenic pruritus” or "functional itch disorder", where psychological factors may contribute to awareness of itching.

Ingestion of helminth (worm) "Enterobius vermicularis" (pinworm, or threadworm) eggs leads to enterobiasis, indicative of severe itching around the anus from migration of gravid females from the bowel. Severe cases of enterobiasis result in hemorrhage and eczema.

Nasal polyps resulting from chronic rhinosinusitis affect approximately 4.3% of the population. Nasal polyps occur more frequently in men than women and are more common as people get older, increasing drastically after the age of 40.

Of people with chronic rhinosinusitis, 10% to 54% also have allergies. An estimated 40% to 80% of people with sensitivity to aspirin will develop nasal polyposis. In people with cystic fibrosis, nasal polyps are noted in 37% to 48%.

Sinusitis is a common condition, with between 24 and 31 million cases occurring in the United States annually. Chronic sinusitis affects approximately 12.5% of people.