A cholesteatoma is a cyst or sac of skin that is growing backwards behind your eardrum into the middle ear and mastoid. It results in a chronic, smelly discharge, and the longer it remains the more damage it can do to the delicate structures of the ear.

If left untreated, after many years it could destroy your hearing, destroy your balance organ and damage your facial nerve which would give you a paralysed side of your face. It can also cause brain infections, because the ear is so close to the brain. It is therefore necessary to remove it, before it is able to cause such damage.