3 doctors weighed in: Can post nasal drip result in mucus entering into lungs and accumulating there, or does it just go in stomach ? 3 doctors weighed in Want a second opinion? A little post nasal drip may try to enter the lungs & trigger a strong protective cough. If it went in with any volume you would have a significant pneumonia almost immediately. Most enters the esophagus/stomach & digestive pathway to be broken down over time.