When humans get the common cold, a common symptom is a stuffy or runny nose. Is that the body's immune response or is that the virus's doing?
There are different causes and mechanisms behind runny and stuffy nose. I cover them separately below.
My professor of pathoanatomy and pathophysiology says that the correct answer here is serous inflammation to the runny nose.
Acute viral respiratory infection
The other answers mostly discusses about the mechanisms (secondary), but not the cause itself. The most upvoted answer describes factors affecting the inflammation but not explicitly mention serous inflammation and its factors.
Congestion in nose is a passive and local process resulting from reduced outflow of blood from a nasal tissue. The nasal epithelium is very thin which makes it vulnerable to flu and cold. The viral particle passes through the membrane (often because of scarring) and causes the change in the vascular permeability of the surrounding big vein.
Mechanisms of stuffy nose are covered partially by Ram and Aleadam:
which respond against viral particles and cause
Stuffy nose is about the reduced outflow of blood from a nasal tissue i.e. isolated venous obstruction. Even small obstruction (scarring) can lead to it. I know no safe systemic medication that can prevent the change of vascular permeability of the nasal big vein. Local steroids like Nasonex improve the recovery time by reducing the congestion when taken during long term - however, it cannot prevent the vascular permeability change of the large vein.
I have an intuition that the the nasal venous congestion can be relieved by the systemic lymphatic drainage massage by special movements involving
which help to drain the accumulated fluid from the nasal tissues. I know no substitute or medication to replace the stimulation of lymphatic drainage.
Prophylactics for the symptoms
You can oil your membranes but to oil them all even at the back side is difficult - even more difficult if have to have them oiled continuously. So there remains some membranes unoiled. I think it takes rather much time for the venous side to recover. Therefore, you feel you feel stuffy nose long time after the runny nose has ended. Local oiling is not enough during cold and allergic times for many patients.
Some medicines for Prophylactics
It's mainly caused by swelling of large veins and by an increase in vascular permeability that leads to an accumulation of fluids in the nasal mucosa. These effects are mediated, at least in part, by bradykinin and histamine, and can be counteracted by epinephrine. These mediators are part of the immune response to the viral particles.
You can read more about it here:
The stuffiness is due to edema or swelling of the mucous membrane covering the nasal cavity. The swelling is caused by vasodialatation or dialatation of the capillaries and leaky vessels which accumulate fluid within the mucous membrane. The runny nose is mainly due to hyperactivity of the mucous cells of the lining which causes vastly more secretion than normal, triggered by the inflammatory reaction to the infection.