What is sinus congestion?

Painful sensation: from engorgement of nasal and sinus mucous membranes, most of the time secondary to allergies, but infection also does it

Good question!: The answer is basically inflammation but what does that mean? It means that when our nasal passages are exposed to allergens, viruses, bacteria or even environmental changes (weather, altitude), the blood vessels dilate and this alone can cause mild "congestion." With infection or allergies, cells from the immune system are recruited to the area and bring water/fluid to the nasal tissues.