Hello Casey, welcome to the forum. If you go to general discussions and scroll down a bit, look for “cleaning your Hohner 26” or “giving your Melodica a bath” there are helpful suggestions. I personally open the Melodica up and if not to bad I simply rub a little alcohol or disinfectant let it dry completely and wash the mouth pieces completely. If you open it and it is really dirty, try some of the suggestion given by Lowboy or Alan.
Monsters of Melodica