Sinus Development in Children

According to the American Academy of Pediatrics, or AAP, the paranasal sinuses, made up of the ethmoid, maxillary, sphenoid and frontal sinuses, are a common site of infection in children and adolescents.These hollow cavities found in the skull are lined with mucous membranes and help to decrease the weight of the skull while warming and filtering air that enters the nose and mouth. These sinuses develop at different stages of life, starting in the fetus and ending near age 20.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Before Birth

The ethmoid and maxillary sinuses form during the third and fourth month of gestation. At birth these sinuses are the size of a pea. The ethmoid sinuses are located on each side of the nose, between the eyes. Made of very thin bone, they grow to their adult size, about the size of a matchbox, by adolescence. The maxillary sinuses are in each cheek, sitting above the teeth and below the eyes. They too reach adult size by adolescence.

Before 5 Years

The sphenoid sinuses begins to form at age 2, and are air-filled and visible on X-rays by age 5. The sphenoid sinuses sit behind the eyes and are located deeper than the other sinuses, behind the ethmoid sinuses. The right and left sphenoid are next to each other, only separated by the septum, a thin plate of bone. They reach adult size, about the size of a large grape, by adolescence.

Before 8 Years

The frontal sinuses develop last, starting around age 4. They are air-filled cavities located in the forehead. Their size and shape differ for each person. They appear on X-rays near age 7 or 8, and do not fully develop until adolescence. They continue to grow until about age 20.


According to the AAP, the paranasal sinuses are often a site of infection in children and adolescents. These infections are often a cause of sickness. For example, the AAP estimates children have six to eight upper-respiratory infections, or colds, every year and that 5 to 13 percent of these are further complicated by infections in the paranasal sinuses. Knowledge and understanding of the development of the paranasal sinuses have enabled doctors to more effectively treat these infections in children and adolescents. For example, doctors know that in early childhood infections usually involve the ethmoid and maxillary sinuses, as they are already formed.

Suspected Infection

According to the American Academy of Otolaryngology, there are a variety of symptoms that may indicate a sinus infection in a child 3. This includes cold symptoms lasting more than 10 to 14 days, sometimes with a low fever. This extended length of sickness is an important difference between the common cold, often present in children, and a sinus infection. Thick yellow or green nasal drainage, a headache in children age six or older and swelling around the eyes can also signal an infection. Lastly, post-nasal drip, which can lead to a sore throat, cough, bad breath and nausea or vomiting can also mean your child has a sinus infection.