Post-nasal drip happens when mucus builds up in the back of the nose and throat. Post-nasal drip is not a medical condition, but it may be a symptom of another medical condition that causes excessive mucus production (e.g., sinusitis, rhinitis, or infections).
The inside lining of the nose produces large amounts of mucus to clean the nose, trap foreign particles (e.g., dust), and to fight infection. Post-nasal drip can be caused by various medical conditions including sinusitis (inflammation of the sinuses), viral infections such as the common cold, rhinitis (a runny nose that may be acute or chronic), allergies, or bacterial infections. In some cases, post-nasal drip can be caused by reflux, or gastroesophageal reflux disease (GERD).
People who experience post-nasal drip often describe a feeling of mucus dripping at the back of the throat. This may lead to frequent throat clearing, sore throat, and coughing. Since post-nasal drip is a symptom of another condition, other symptoms may be present that are linked to whatever's causing the problem. When allergies are responsible for post-nasal drip, many people experience teary eyes, itchiness of the nose and eyes, and headaches. If you have asthma, the post-nasal drip may make breathing even more difficult.
Other symptoms associated with post-nasal drip may include bad breath, stuffy nose, hoarse voice, or coughing.