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Sinuses are hollow air spaces in the human body. When people say,
"I'm having a sinus attack," they usually are referring
to symptoms in one or more of four pairs of cavities, or sinuses,
known as paranasal sinuses. These cavities, located within the
skull or bones of the head surrounding the nose, include the:
- Frontal sinuses over the eyes in the brow
area
- Maxillary sinuses inside each cheekbone
- Ethmoid sinuses just behind the bridge of the nose and between
the eyes
- Sphenoid sinuses behind the ethmoids in the upper region of
the nose and behind the eyes
Each sinus has an opening into the nose for
the free exchange of air and mucus, and each is joined with the
nasal passages by a continuous mucous membrane lining. Therefore,
anything that causes a swelling in the nose-an infection, an allergic
reaction, or an immune reaction-also can affect the sinuses. Air
trapped within a blocked sinus, along with pus or other secretions,
may cause pressure on the sinus wall. The result is the sometimes
intense pain of a sinus attack. Similarly, when air is prevented
from entering a paranasal sinus by a swollen membrane at the opening,
a vacuum can be created that also causes pain.
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