What is postnasal drip? Postnasal drip develops when too much mucus collects at the back of the nose or in the throat. It usually creates the sensation of a “tickle” or itch in the throat that won’t go away. The mucus can be clear and watery or thick with a green, yellow, or white color. The discomfort associated with postnasal drip usually leads to coughing, throat clearing, and watery eyes. In people with asthma, postnasal drip can make it difficult to breathe. Causes of postnasal drip include allergies, the common cold, and the flu. It also sometimes accompanies other respiratory bacterial or viral infections or can be brought on by simple irritation, such as eating very spicy foods. Certain medications can cause postnasal drip, such as drugs containing estrogen. Postnasal drip is not life threatening and usually resolves on its own. However, if the symptom lasts more than a few weeks, and if it is accompanied by foul-smelling discharge, fever, or difficulty breathing, you should contact a medical professional to identify the cause. Seek prompt medical care if you have facial lumps or a nonhealing sore in your nose, loose or painful upper teeth, a persistent or mucus-producing cough with sore throat, white patches and redness on your tongue or in your mouth, a persistent fever, or a feeling of something stuck in your throat that will not go away.