Some people get fluid behind the eardrum. This is sometimes called glue ear. It is very common in young children, but it can happen in adults too. We don't know exactly what causes glue ear.
Most young children will have glue ear at some time, but it doesn't always cause problems. We only need to treat it if it is causing problems with hearing or speech, or if it is causing lots of ear infections.

Grommets usually fall out by themselves as the eardrum grows. They may stay in for six months, or a year, or sometimes even longer. You may not notice when they drop out.