Post-nasal drip refers to mucus from the nasal cavity or sinuses flowing backwards into the throat. In fact, the lining from the nose to the throat produces mucus every day to keep the nasal passages and throat moist, and to help clear away dust, germs and irritants. Some of this mucus naturally flows down the throat and into the stomach, which is a normal physiological process.
However, when there is excessive mucus production, swelling of the nasal lining, or mucus becomes too thick, post-nasal drip may become more noticeable. Patients may feel as if there is phlegm in the throat, need to clear the throat frequently, or develop cough or hoarseness.
Common causes of post-nasal drip include infectious rhinitis, such as the common cold, influenza, adenovirus or RSV infection. It may also be caused by allergic rhinitis. Sinusitis, deviated nasal septum, and medication-induced rhinitis caused by frequent or prolonged use of decongestant nasal sprays may also affect normal mucus drainage and worsen post-nasal drip. Cold, dry air or certain medications, such as some antihistamines, may also make mucus thicker.
Patients with post-nasal drip often feel that there is phlegm or a foreign-body sensation in the throat, or may need to clear the throat repeatedly. Some people may develop a cough, especially when lying down or after waking up.
Other symptoms may include hoarseness, throat irritation, nausea, a feeling of wanting to vomit, and stronger odour from the mouth or nose. If symptoms are accompanied by nasal congestion, runny nose, sneezing or itchy nose, allergic rhinitis may be involved. If the mucus becomes thick, yellowish or purulent, and is associated with facial pressure or fever, sinusitis may be a possible cause.
Post-nasal drip is not always a serious problem. However, if symptoms persist, do not improve after treatment, or keep recurring, patients should consult a doctor to assess whether it may be related to nasal allergy, sinusitis, deviated nasal septum, acid reflux or other respiratory problems.
Medical attention should be sought promptly if there is fever, thick yellow mucus with an unpleasant smell, shortness of breath, wheezing, or worsening cough. These symptoms may be related to acute sinusitis, influenza, other respiratory infections or an allergic flare-up.
If nasal discharge or phlegm remains abnormal for a long time, has a persistent unpleasant smell, or is associated with blood-stained mucus, weight loss, one-sided nasal blockage or a neck lump, medical assessment is recommended to rule out more serious conditions involving the nasopharynx, respiratory tract or lungs.
In daily life, patients may keep indoor air moist, avoid smoke and air pollutants, reduce exposure to known allergens, and avoid using decongestant nasal sprays for a prolonged period without medical advice, as this may worsen nasal congestion or rhinitis.
