According to the American Academy of Allergy, Asthma and Immunology, allergies affect 40 million to 50 million people per year and can have a serious impact on a person's quality of life. Allergic rhinitis, or a runny nose caused by a response to an allergen, is a common cause of post-nasal drip. The nose typically produces mucus to trap foreign substances such as dust, pet dander, pollen, bacteria and viruses. When the nose produces too much mucus, the mucus runs down the back of the throat, which can be uncomfortable and cause a cough.
Causes of Allergic Rhinitis
According to the National Institute of Allergy and Infectious Diseases (NIAID), allergic rhinitis occurs when an allergen-sensitive person inhales an allergen. An allergen can be any substance that causes a person's body to respond inappropriately. When the body encounters the allergen, it generates large amounts of an antibody called immunoglobulin E, or IgE. These antibodies are unique in that they bind tightly to mast cells, a special type of cell that releases histamine. This histamine release results in inflammation and causes many of the symptoms of allergic rhinitis, including sneezing, runny nose and itchy eyes. People who develop seasonal allergic rhinitis typically are sensitive to outdoor allergens.
Symptoms of Post-Nasal Drip
Post-nasal drip is one of the common results of allergic rhinitis. When excessive mucus is produced as a response to the allergen, the mucus drips down the back of the throat. This can result in constant swallowing of mucus, a tickling in the back of the throat, chronic sore throat, chronic cough and bad breath. When a physician examines a patient with post-nasal drip, he typically sees a pattern on the back of the throat that is referred to as "cobblestoning."
Other Causes of Post-Nasal Drip
Post-nasal drip can be caused by any process that results in increased mucus. The most common causes other than allergic rhinitis include non-allergic (vasomotor) rhinitis and sinusitis. Non-allergic rhinitis can be suspected in an older patient who previously has not had allergies or in a patient with negative skin testing to allergens. Gastroesophageal reflux disease, or the reflux of stomach acid back up into the esophagus, can cause similar symptoms and may be misdiagnosed as post-nasal drip. It is important to differentiate among these disorders because the treatment for each is different.
Treatments that decrease mucus production in allergic rhinitis help to resolve the symptoms of post-nasal drip. Inhaled corticosteroids tend to be the most effective drug therapy; they reduce nasal congestion directly through an anti-inflammatory effect. Antihistamines are medications that reduce the histamine response and therefore help to relieve allergy symptoms. However, these medications may cause drowsiness and also have the side effect of dry mouth. Nasal sprays such as saline drops and a neti pot can be used for nasal irrigation to reduce the burden of nasal mucus, but these treatments improve symptoms without improving the overall disease.
If post-nasal drip does not improve with treatment of allergic rhinitis, it is important to consider other causes. Chronic sinusitis can be evaluated by an ear, nose and throat physician and can be treated with antibiotics and even with surgery if there is an abnormality causing the sinusitis. Vasomotor rhinitis can be treated with a nasal steroid. Avoidance of triggers such as spicy foods, changes in weather or occupational exposures can be helpful as well.