The adenoids are made up of a group of blood cells that create antibodies, which are proteins that neutralize foreign substances in the body. Unlike the tonsils that are easy to see in the mouth, the adenoids are located at the back part of the nasal cavity, behind the soft palate. When infection or inflammation occurs, the adenoids can enlarge. Since they are seated at the back of the nasal cavity, the swollen adenoids can block airflow through the nose. The exact cause of enlarged adenoids is not always clear.
Most studies point to chronic infection of the upper respiratory tract.
The adenoids can also enlarge from chronic irritation when infected or inflamed nasal secretions are constantly swept back over it. Allergies may also cause enlargement of the adenoids. Adenoid enlargement is more common in children than adults. There is no way to prevent this condition. In young children, the easiest way to find an enlarged adenoid is with an x-ray.