Reflux causes throat irritation, leading to a sensation of increased mucus in the throat, which 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. Causes
There are multiple causes of PND, which can be acute or chronic. Allergic rhinitis
Allergic rhinitis (AR) is a common condition where exposure to allergens results in the release of inflammatory mediators, such as histamine, that causes sneezing, rhinorrhea, itchy eyes, and nasal congestion. The increased rhinorrhea and mucus production can result in PND. Non-allergic rhinitis
Non-allergic rhinitis (NAR) is a condition in which there are symptoms of rhinitis, including rhinorrhea and nasal obstruction, but with negative skin and serum allergy testing results. It can be further categorized into:
Non-allergic rhinitis with eosinophilia (NARES)
Hormonal rhinitis (such as during pregnancy)
Medication-induced rhinitis
Atrophic rhinitis
Irritant and occupational rhinitis (including tobacco smoke, cleaning supplies, etc.) Idiopathic nonallergic rhinitis

Rhinosinusitis
Rhinosinusitis is inflammation or infection of the sinus cavities. Acute rhinosinusitis has symptoms lasting less than four weeks, while chronic rhinosinusitis lasts greater than 12 weeks. This persistent irritation can lead to increased mucus production as a result of pro-inflammatory pathways, producing symptoms of PND. Mechanism
The exact mechanism of PND depends on its etiology, but usually involves increased production of mucus from the nasal mucosa. In addition to providing sense of smell, the nasal cavity serves to filter and regulate the temperature and humidity of inspired air. The nasal mucosa can produce secretions, or mucus, that provides lubrication and protection for the nasal cavity.
Antibiotics may be prescribed if the PND is the result of bacterial sinusitis. In cases where PND is caused by allergic rhinitis or irritant rhinitis, avoidance of allergens or irritating factors such as dander, cigarette smoke, and cleaning supplies may be beneficial. Antihistamines are particularly useful for allergic rhinitis, and it may be beneficial in some cases of non-allergic rhinitis. First-generation antihistamines such as chlorpheniramine and clemastine are more potent but have greater sedatory effects; later-generation antihistamines may be used to reduce these effects. Azelastine, a topical antihistamine, is approved for both allergic and non-allergic rhinitis due to its unique anti-inflammatory effects separate from its histamine receptor antagonism.Intranasal steroids may also be beneficial in patients who do not respond to antihistamines. In one meta-analysis, intranasal steroids were shown to improve symptoms of non-allergic rhinitis at four weeks better than a placebo. Decongestants such as pseudoephedrine can tighten blood vessels of the nasal mucosa and result in a decrease in mucus production. Anticholinergics such as ipratropium bromide can help reduce secretions by blocking parasympathetic effects on the nasal mucosa.Other methods, such as drinking warm fluids and using saline nasal irrigation, may be useful for managing symptoms of PND but its exact efficacy is unclear in medical literature. Epidemiology
Because PND is often characterized as a "symptom" rather than a separate condition, the exact incidence is unknown and varies by its etiology. Chronic rhinitis, which includes allergic and non-allergic rhinitis, can affect 30-40% of the population. Non-allergic rhinitis is more common in females than in males.