The sinuses are hollow cavities within the facial bones. Sinuses are not fully developed until after age twelve. When people speak of sinus infections, they are most frequently referring to the maxillary and frontal sinuses.
Seth Schwartz, MD, MPH, Otolaryngologist, Virginia Mason Medical Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.