The sinuses are hollow cavities within the facial bones. Sinuses are not fully developed until after age 12. When people speak of sinus infections, they are most frequently referring to the maxillary and ethmoid sinuses.
Review Date 4/13/2020
Updated by: Josef Shargorodsky, MD, MPH, Johns Hopkins University School of Medicine, Baltimore, MD. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.