Increased nasal mucus occurs when the tissues lining the nose or sinuses become irritated and swell or grow abnormally. Viral and bacterial infections, allergies, environmental irritants and nasal polyps are among the most common causes of runny nose, also known as rhinitis, and postnasal drip. Treatments to alleviate rhinitis or postnasal drip vary, depending on the underlying causes.
Upper-respiratory Infections
Upper-respiratory infections remain the most common cause of runny nose, with roughly 1 billion head colds occurring annually in the United States, according to the National Institute of Allergy and Infectious Diseases. Viral or bacterial sinusitis also prove to be frequent causes of increased nasal mucus. Influenza, chicken pox, whooping cough, measles, rubella and roseola characteristically cause upper-respiratory symptoms, including runny nose, notes the Mayo Clinic.
Allergies
A runny nose caused by an allergy is known as allergic rhinitis. Up to 30 percent of American adults and 40 percent of children have allergic rhinitis, the American Academy of Allergy, Asthma and Immunology reports. An immune-system reaction to various types of inhaled particles causes swelling of the nasal tissues and increased nasal discharge. Sneezing, itchy eyes and excessive tearing frequently accompany allergic rhinitis, also known as hay fever.
Common causes, or triggers, of allergic rhinitis include tree and plant pollens, pet dander, molds, cockroach droppings, cigarette smoke, dust mites and fragrances. Allergic rhinitis may be year-round or seasonal, depending on the allergic triggers. Treatment includes avoidance of substances that provoke symptoms, nasal steroid sprays, antihistamines and antileukotriene medications. Allergy shots may provide relief for people with severe, year-round symptoms.
Environmental Irritants
Inhaled environmental irritants can cause inflammation of the nasal tissues, leading to increased nasal mucus and runny nose. This condition is known as nonallergic rhinitis. This form of rhinitis most commonly occurs in adults, notes the American Academy of Allergy, Asthma and Immunology. Smoke, pollution and pungent odors frequently precipitate nonallergic rhinitis in susceptible individuals.
Medications may also cause nonallergic rhinitis, including certain beta-blockers for high blood pressure, nonsteroidal anti-inflammatory drugs, antidepressants, drugs for erectile dysfunction, sedatives and birth-control pills. Prolonged use of nasal-decongestant sprays can provoke rebound rhinitis when the drug is stopped.
Nasal Polyps
Nasal polyps are small growths on the lining tissues of the nose and sinuses. These noncancerous growths may cause runny nose, nasal stuffiness, postnasal drip, blocked airflow and a decreased sense of smell and taste. Although no identifiable cause can be determined in most cases of nasal polyps, people with asthma and an aspirin allergy commonly develop them. Topical nasal steroids often reduce the size of nasal polyps, relieving symptoms. Large or troublesome nasal polyps may require surgical removal.
References
- National Institute of Allergy and Infectious Diseases: Common Cold Overview
- MayoClinic.com: Runny Nose
- American Academy of Otolaryngology--Head and Neck Surgery: Allergic Rhinitis, Sinusitis, and Rhinosinusitis
- American Academy of Allergy, Asthma & Immunology: Tips to Remember, Rhinitis
- MayoClinic.com: Nonallergic Rhinitis
