Nasal congestion can be caused by anything that irritates or inflames the nasal tissues. Infections — such as colds, flu or sinusitis — and allergies are frequent causes of nasal congestion and runny nose. Sometimes a congested and runny nose can be caused by irritants such as tobacco smoke and car exhaust.

Where does the fluid in your sinuses come from?

Mucus is made by mucosal glands that line the body's respiratory tract, which includes the nose, the throat and the lungs, Lebowitz said. Related: Why do we sneeze? Most of the mucus that people sneeze out comes from the mucosal glands lining the nasal passages, Lebowitz said.

Does Covid 19 cause sinus mucus?

Can Covid-19 Cause a Sinus Infection? COVID-19 is a disease that can cause what doctors call a respiratory tract infection. It can affect your upper respiratory tract (sinuses, nose, and throat) or lower respiratory tract (windpipe and lungs). There is no information yet on whether COVID-19 causes sinusitis.