The sinuses are air-filled cavities within the bony confines of the skull whose purpose has yet to be defined. Their delicate mucosal surface is highly susceptible to the inflammation caused by allergic reactions to outside irritants – dust, mold, pollen, pet dander, chemicals, smoke, etc. When the tissues lining the sinus become swollen, known as Sinusitis, fluid begins to collect instead of draining naturally. The end result is facial pressure, nasal drainage, and with enough time to allow bacterial overgrowth, infection.