Absolute eosinophil count, nasal smear, skin and in vitro allergy tests to rule out allergic rhinitis, acoustic rhinometry for measuring nasal patency, smell testing, CT scan in cases of sinus disease and MRI in case of mass lesions.

The avoidance of inciting factors such as sudden changes in temperature, humidity, or blasts of air or dust is helpful.

Intranasal application of antihistamines, corticosteroids, or anticholinergics may also be used for vasomotor rhinitis. Intranasal cromolyn sodium may be used in patients older than two years.

Astelin (Azelastine) "is indicated for symptomatic treatment of vasomotor rhinitis including rhinorrhea, nasal congestion, and post nasal drip in adults and children 12 years of age and older."

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.

In the case of infectious rhinitis, vaccination against influenza viruses, adenoviruses, measles, rubella, "Streptococcus pneumoniae", "Haemophilus influenzae", diphtheria, "Bacillus anthracis", and "Bordetella pertussis" may help prevent it.

Allergy testing may reveal the specific allergens to which an individual is sensitive. Skin testing is the most common method of allergy testing. This may include a patch test to determine if a particular substance is causing the rhinitis, or an intradermal, scratch, or other test. Less commonly, the suspected allergen is dissolved and dropped onto the lower eyelid as a means of testing for allergies. This test should be done only by a physician, since it can be harmful if done improperly. In some individuals not able to undergo skin testing (as determined by the doctor), the RAST blood test may be helpful in determining specific allergen sensitivity. Peripheral eosinophilia can be seen in differential leukocyte count.

Allergy testing can either show allergies that are not actually causing symptoms or miss allergies that do cause symptoms. The intradermal allergy test is more sensitive than the skin prick test but is more often positive in people that do not have symptoms to that allergen.

Even if a person has negative skin-prick, intradermal and blood tests for allergies, he/she may still have allergic rhinitis, from a local allergy in the nose. This is called local allergic rhinitis. Specialized testing is necessary to diagnose local allergic rhinitis.

Extreme deviation of nasal septum may be accompanied by atrophic rhinitis on the wider side.

One way to prevent allergic rhinitis is to wear a respirator or mask when near potential allergens.

Growing up on a farm and having multiple brothers and or sisters decreases the risk.

Urinary cystyl-leukotriene or urinary LTE4 can be used after a supervised challenge with aspirin. In aspirin sensitivity, no change in N-methylhistamine is observed; while LTE4 levels are increased. This test however lacks sensitivity and has a 25 percent false negative rate among affected persons.

In most cases treatment for rhinorrhea is not necessary since it will clear up on its own—especially if it is the symptom of an infection. For general cases blowing your nose can get rid of the mucus buildup. Though blowing may be a quick-fix solution, it would likely proliferate mucosal production in the sinuses, leading to frequent and higher mucus buildups in the nose. Alternatively, saline nasal sprays and vasoconstrictor nasal sprays may also be used, but may become counterproductive after several days of use, causing rhinitis medicamentosa.

In recurring cases, such as those due to allergies, there are medicinal treatments available. For cases caused by histamine buildup, several types of antihistamines can be obtained relatively cheaply from drugstores.

People who prefer to keep clear nasal passages, such as singers, who need a clear nasal passage to perform, may use a technique called "nasal irrigation" to prevent rhinorrhea. Nasal irrigation involves rinsing the nasal cavity regularly with salty water or store bought saline solutions.

The treatment of RM involves withdrawal of the offending nasal spray or oral medication. Both a "cold turkey" and a "weaning" approach can be used. Cold turkey is the most effective treatment method, as it directly removes the cause of the condition, yet the time period between the discontinuation of the drug and the relief of symptoms may be too long and uncomfortable for some individuals (particularly when trying to go to sleep when they are unable to breathe through their nose).

A benefit of the gradual “weaning” approach is that it helps preserve normal nasal airflow during the withdrawal process. United States Patent Number 5,988,870 was issued for a method and apparatus used to facilitate the precise titration and gradual withdrawal of decongestant nasal sprays containing addictive compounds. The system is sold under the brand name Rhinostat.

The use of over-the-counter (OTC) saline nasal sprays may help open the nose without causing RM if the spray does not contain a decongestant. Symptoms of congestion and runny nose can often be treated with corticosteroid nasal sprays under the supervision of a physician. For very severe cases, oral steroids or nasal surgery may be necessary.

For RM caused by topical decongestants, there are anecdotal reports of persons having success by withdrawing treatment from one nostril at a time.

A study has shown that the anti-infective agent benzalkonium chloride, which is frequently added to topical nasal sprays as a preservative, aggravates the condition by further increasing the rebound swelling.

Effective management of allergic diseases relies on the ability to make an accurate diagnosis. Allergy testing can help confirm or rule out allergies. Correct diagnosis, counseling, and avoidance advice based on valid allergy test results reduces the incidence of symptoms and need for medications, and improves quality of life. To assess the presence of allergen-specific IgE antibodies, two different methods can be used: a skin prick test, or an allergy blood test. Both methods are recommended, and they have similar diagnostic value.

Skin prick tests and blood tests are equally cost-effective, and health economic evidence shows that both tests were cost-effective compared with no test. Also, early and more accurate diagnoses save cost due to reduced consultations, referrals to secondary care, misdiagnosis, and emergency admissions.

Allergy undergoes dynamic changes over time. Regular allergy testing of relevant allergens provides information on if and how patient management can be changed, in order to improve health and quality of life. Annual testing is often the practice for determining whether allergy to milk, egg, soy, and wheat have been outgrown, and the testing interval is extended to 2–3 years for allergy to peanut, tree nuts, fish, and crustacean shellfish. Results of follow-up testing can guide decision-making regarding whether and when it is safe to introduce or re-introduce allergenic food into the diet.

An allergy blood test is quick and simple, and can be ordered by a licensed health care provider ("e.g.", an allergy specialist), GP, or PED. Unlike skin-prick testing, a blood test can be performed irrespective of age, skin condition, medication, symptom, disease activity, and pregnancy. Adults and children of any age can take an allergy blood test. For babies and very young children, a single needle stick for allergy blood testing is often more gentle than several skin tests.

An allergy blood test is available through most laboratories. A sample of the patient's blood is sent to a laboratory for analysis, and the results are sent back a few days later. Multiple allergens can be detected with a single blood sample. Allergy blood tests are very safe, since the person is not exposed to any allergens during the testing procedure.

The test measures the concentration of specific IgE antibodies in the blood. Quantitative IgE test results increase the possibility of ranking how different substances may affect symptoms. A rule of thumb is that the higher the IgE antibody value, the greater the likelihood of symptoms. Allergens found at low levels that today do not result in symptoms can nevertheless help predict future symptom development. The quantitative allergy blood result can help determine what a patient is allergic to, help predict and follow the disease development, estimate the risk of a severe reaction, and explain cross-reactivity.

A low total IgE level is not adequate to rule out sensitization to commonly inhaled allergens. Statistical methods, such as ROC curves, predictive value calculations, and likelihood ratios have been used to examine the relationship of various testing methods to each other. These methods have shown that patients with a high total IgE have a high probability of allergic sensitization, but further investigation with allergy tests for specific IgE antibodies for a carefully chosen of allergens is often warranted.

Laboratory methods to measure specific IgE antibodies for allergy testing include enzyme-linked immunosorbent assay (ELISA, or EIA), radioallergosorbent test (RAST) and fluorescent enzyme immunoassay (FEIA).

Rhinorrhea can occur as a symptom of opioid withdrawal accompanied by lacrimation. Other causes include cystic fibrosis, whooping cough, nasal tumors, hormonal changes, and cluster headaches. Due to changes in clinical practice, Rhinorrhea is now reported as a frequent side effect of oxygen-intubation during colonoscopy procedures [A simple, innovative way to reduce rhinitis symptoms after sedation during endoscopy" by Nai-Liang Li, et al, Canadian Journal of Gastroenterology, 2011, Feb; volume 25(2): pages 68–72.]. Rhinorrhea can also be the side effect of several genetic disorders, such as primary ciliary dyskinesia.

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.

Some people have reported relief of symptoms by following a low-salicylate diet such as the Feingold diet. Aspirin is quickly converted in the body to salicylic acid, also known as 2-Hydroxybenzoic acid. Sommer "et al." reported a multi-center prospective randomized cross-over trial with 30 patients following a low-salicylate diet for 6 weeks. This study demonstrated a clinically significant decrease in both subjective and objective scoring of severity of disease, but made note of the challenge for patients in following what is a fairly stringent diet.

A diet low in omega-6 oils (precursors of arachidonic acid), and high in omega-3 oils, may also help. In a small study, aspirin-sensitive asthma patients taking 10 grams of fish oil daily reported relief of most symptoms after six weeks, however symptoms returned if the supplement was stopped.

Rhinitis medicamentosa (or RM) is a condition of rebound nasal congestion brought on by extended use of topical decongestants (e.g., oxymetazoline, phenylephrine, xylometazoline, and naphazoline nasal sprays) and certain oral medications (e.g., sympathomimetic amines and various 2-imidazolines) that constrict blood vessels in the lining of the nose.

Treatment of atrophic rhinitis can be either medical or surgical.

Medical measures include:

- Nasal irrigation using normal saline

- Nasal irrigation and removal of crusts using alkaline nasal solutions prepared by dissolving a spoonful of powder containing one part sodium bicarbonate, one part sodium biborate and two part sodium chloride.

- 25% glucose in glycerine can be applied to the nasal mucosa to inhibit the growth of proteolytic organisms which produce foul smell.

- Local antibiotics, such as chloromycetine.

- Vitamin D (Kemicetine).

- Estradiol spray for regeneration of seromucinous glands and vascularization of mucosa.

- Systemic streptomycin (1g/day) against Klebsiella organisms.

- Oral potassium iodide for liquefaction of secretion.

- Placental extract injected in the submucosa.

Surgical interventions include:

- Young's operation.

- Modified Young's operation.

- Narrowing of nasal cavities, submucosal injection of Teflon paste, section and medial displacement of the lateral wall of the nose.

- Transposition of parotid duct to maxillary sinus or nasal mucosa.

Nasal obstruction characterized by insufficient airflow through the nose can be a subjective sensation or the result of objective pathology. It is difficult to quantify by subjective complaints or clinical examinations alone, hence both clinicians and researchers depend both on concurrent subjective assessment and on objective measurement of the nasal airway. Often a doctor's assessment of a perfectly patent nasal airway might differ with a patient's complaint of an obstructed nose.

Diagnosis of alcohol-induced respiratory symptoms can be strongly suggested on the bases of survey questionnaires. Questionnaires can be devised to determine the specific types of alcoholic beverages eliciting reactions; reactions evoked by one or only a few but not other types of alcoholic beverage, particularly when the offending beverage(s) is wine and/or beer, suggest that the reactions are due to classical allergic reaction to allergens in the beverage; reactions to all or most types of alcoholic beverages favors a genetic (i.e. acetaldehyde-induce) basis. Further differentiation between these two causes can be tested under medical supervision be determining if ingestion of a water-diluted pure ethanol solution elicits reactions or if an offending alcoholic beverage but not the same beverage without ethanol elicits reactions. Either result would favor an acetaldehyde-induced genetic basis for the reaction.

Diagnosis of alcohol sensitivity due to the accumulation of acetaldehyde in individuals bearing the glu487lys ALDH2 allele can be made by measuring the diameter of the erythema (i.e. red) area developing under a 15 millimeter skin patch plaster soaked in 70% ethanol and applied for 48 hours (ethanol patch test); erythema of 15 millimeters is considered positive with a false positive ratio ([100 x {number of individuals with a positive patch test}]/{number of individuals with a normal ALDH2 genotype}) of 5.9% and a false negative ratio ([100 x {number of individuals with a negative patch test}]/{number of individuals with a glu487lys ALDH2 allele}) of 0%. To resolve ambiguities in or replace the ethanol patch test for other reasons, a polymerase chain reaction using special primers and conditions can be used to directly detect the glu487lys ALDH2 genes. For other causes of acetaldehyde-induced alcohol sensitivities, the ethanol patch test will need to be tested for verification of its acetaldehyde basis and appropriate polymerase chain reactions will likewise be needed to verify a genetic basis for symptoms.

Diagnosis of alcohol sensitivity due to allergic reactivity to the allergens in alcoholic beverages can be confirmed by standard skin prick tests, skin patch tests, blood tests, challenge tests, and challenge/elimination tests as conducted for determining the allergen causing other classical allergic reactions (see allergy and Skin allergy tests.)

Good oral hygiene (thorough tooth brushing and flossing and regular professional cleaning and examination) may be helpful to prevent these disorders. Drinking plenty of water and the production of enough saliva, aid in the reduction of bacterial growth. Minimizing irritants or injury in the mouth when possible can aid in the prevention of glossitis. Avoiding excessive use of any food or substance that irritates the mouth or tongue may also help.

Lichen planus has a unique microscopic appearance that is similar between cutaneous, mucosal and oral. A Periodic acid-Schiff stain of the biopsy may be used to visualise the specimen. Histological features seen include:

- thickening of the stratum corneum both with nuclei present (parakeratosis) and without (orthokeratosis). Parakeratosis is more common in oral variants of lichen planus.

- thickening of the stratum granulosum

- thickening of the stratum spinosum (acanthosis) with formation of colloid bodies (also known as Civatte bodies, Sabouraud bodies) that may stretch down to the lamina propria.

- liquefactive degeneration of the stratum basale, with separation from the underlying lamina propria, as a result of desmosome loss, creating small spaces (Max Joseph spaces).

- Infiltration of T cells in a band-like pattern into the dermis "hugging" the basal layer.

- Development of a "saw-tooth" appearance of the rete pegs, which is much more common in non-oral forms of lichen planus.

The differential diagnosis for OLP includes:

- Other oral vesiculo-ulcerative conditions such as Pemphigus vulgaris and Benign mucous membrane pemphigoid

- Lupus erythematosus, with lesions more commonly occur on the palate and appear as centrally ulcerated or erythematous with radiating white striae. In contrast, OLP and lichenoid reactions rarely occur on the palate, and the striae are randomly arranged rather than radial.

- Chronic ulcerative stomatitis

- Frictional keratosis and Morsicatio buccarum (chronic cheek biting)

- Oral leukoplakia

- Oral candidiasis

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

Avoidance of ethanol is the safest, surest, and cheapest treatment. Indeed, surveys find a positive correlation between high incidences of glu487lys ALDH2 allele-related alcohol-induced respiratory reactions as well as other causes of these reactions and low levels of alcohol consumption, alcoholism, and alcohol-related diseases. Evidently, people suffering these reaction self-impose avoidance behavior. There is a proviso here: ethanol, at surprisingly high concentrations, is used as a solvent to dissolve many types of medicines and other ingredients. This pertains particularly to liquid cold medicines and mouthwashes. Ethanol avoidance includes avoiding the ingestion of and, depending on an individual's history, mouth washing with, such agents.

Type H1 antagonists in the histamine antagonist family of drugs were tested in Japanese volunteers with alcohol-induced asthma (who presumably have glu487lys ALDH2 allele-associated asthma) and found to be completely effective in blocking bronchoconstriction responses to alcoholic beverages; these blockers, it is suggested, may be taken 1–2 hours before consumption of alcohol beverages as a preventative of alcohol-induced respiratory reactions. In the absence of specific studies on the prevention of classical alcohol induced rhinitis and asthma due to allergens in alcoholic beverages, see asthma section on Prevention and rhinitis section on Prevention of allergen-induced reactions.

In the absence of specific studies on the treatment of acute alcohol-induced bronchoconstriction and rhinitis, treatment guidelines should probably follow those of their comparable allergen-induced classical allergic reactions (see asthma section on Treatment and rhinitis section on Treatment) but possibly favoring the testing of H1 antagonist anti-histamines as part of the initial protocol.

Dermographism can be treated by substances (i.e. an antihistamine) which prevent histamine from causing the reaction. These may need to be given as a combination of H antagonists, or possibly with an H-receptor antagonist such as cimetidine.

OTC Vitamin C, 1000 mg daily, increases histamine degradation and removal.

Not taking hot baths or showers may help if it is generalized (all over) and possibly for localized cases (in a specific area). If taking hot showers helps, it may be a condition called shower eczema. If it affects mainly the head, it may be psoriasis. In rare cases, allergy tests may uncover substances the patient is allergic to.

While cromoglycate, which prevents histamine from being released from mast cells, is used topically in rhinitis and asthma, it is not effective orally for treating chronic urticaria.