Because glands in the mucous membranes are always working to keep the nose moist, some postnasal drip-the flow of fluid from nose to throat-is normal. It becomes a problem when mucus is overproduced and drainage is excessive, making your throat sore and producing a constant need to clear it.
The underlying cause maybe an allergy; an irritant such as smoke, fumes, or a cold: or sinusitis, an inflammation of the mucous membranes of the sinuses.
If sinusitis is the problem, besides postnasal drip, you are likely to have a stuffy nose, headache, pain above the eyes and behind the cheekbones, and thick, greenish mucus. Sinusitis often follows a bad cold. If it is painful or chronic or persists for weeks, consult a doctor.
Postnasal drip is most common in cold weather, when air both outdoors and indoors is low in humidity. If you can, stay indoors when it’s extremely cold. Add moisture to indoor air by means of vaporizers or humidifiers. It may help to blow your nose gently from time to time, even if you feel no need to, and to sleep with your head propped on two pillows.