* The adenoids can become infected as part of a short illness, or can stay swollen over a long time. * Enlarged adenoids can make it more likely that a child will get ear infections because they block the tubes leading to the middle ear. They can also cause sinusitis and may interfere with breathing so the child has to breathe through the mouth and snores at night. * Children with large adenoids are often unable to breathe easily through their nose, so they usually breathe through their mouth (their mouth is always open). Their mouth and lips get dry and they may have 'bad breath'.