The sinuses are a connected system of hollow cavities in the skull. The sinuses are lined with soft, pink tissue called mucosa. Normally, the sinuses are empty except for a thin layer of mucus. The inside of the nose has ridges called turbinates. Normally these structures help humidify and filter air. The nose is divided in the center by a thin wall, called the septum. Most of the sinuses drain into the nose through a small channel or drainage pathway called the middle meatus. The purpose of the sinuses is unclear. One theory is that sinuses help humidify the air we breathe in; another is that they enhance our voices.
 

Sinusitis in children

Sinusitis in children
Sinusitis (rhinosinusitis) in children can look different than sinusitis in adults. More often, children have a cough, bad breath, crankiness, low energy, and swelling around the eyes, along with a thick yellow-green nasal or post-nasal drip.

Child's sinuses are not fully developed until late in the teen years.

Overview of Sinusitis

sinusitis
Sinusitis is an inflammation, or swelling, of the tissue lining the sinuses. Normally, sinuses are filled with air, but when sinuses become blocked and filled with fluid, germs (bacteria, viruses, and fungi) can grow and cause an infection.

Conditions that can cause sinus blockage include the common cold, allergic rhinitis (swelling of the lining of the nose), nasal polyps (small growths in the lining of the nose), or a deviated septum (a shift in the nasal cavity).