What people usually refer to as sinuses are the air pockets in the head. There is one pair of cheek sinuses (maxillary sinuses) and one pair of sinuses between the eyes (ethmoid sinuses), one frontal sinus above the eyes and one sphenoid sinus in the center of the head. They all drain into the nose and nasopharynx. Any or all of them can become infected. Those areas of the face that are overlying the sinuses can sometimes become swollen when the sinuses underneath are infected. The forehead can show some swelling when the frontal sinus is infected. The cheeks can be swollen when the maxillary sinuses are infected. The bridge of the nose can be swollen when the ethmoids are infected.
However, with most sinus infections, there is usually no visible swelling, and when it does occur it is minimal. The reason is that the sinuses are separated from the face by bone. Much more common than swelling is tenderness when the skin over the infected sinus is touched or tapped.
Very rarely, a sinus infection can break through the bone and produce significant facial swelling and redness of the skin. When this happens, an urgent trip to the physician or emergency room is necessary. Antibiotics and sometimes surgery are necessary to clear up the problem.