Harmonicas can become a breeding ground for bacteria and other undesirables because of bacteria and food particles being blown in with warm moist air. It is important for your own health as a harmonica player that you keep your instrument clean and disinfected and use proper hygiene when you play. It will also keep the harmonica in better playing condition. Here are a few methods of cleaning your instrument.
Unscrew the all the screws, putting them somewhere safe so they won't get lost. The two cover plates, two reed plates and the comb will now come apart freely.
Wash the comb with a toothbrush and warm, soapy water. Dry it thoroughly because moisture can cause the metal to tarnish and rust.
Use the same method to clean the cover plates. It is possible to use a metal cleaner or polish on the cover, but most players don't consider this necessary. Tarnish won't hurt anything but the appearance, and a polish can leave an unpleasant chemical smell that is hard to get rid of.
Use your fingers with warm soap and water to wash the reed plates. Be gentle and don't use a brush because it could damage the delicate reeds that are part of these plates. Dry very thoroughly to avoid rust.
Use rubbing alcohol or hydrogen peroxide to disinfect any of the parts with a cotton swab, including the mouthpiece, if desired. It won't kill every type of organism but it will work well for our purposes. Be careful not to leave any fuzz from the cotton swab behind.
Reassemble the harmonica the same way you took it apart.
Buy a cleaning kit for a chromatic harmonica or follow the manufacturer's recommendations for thorough cleaning. You should never soak or run water through a chromatic harmonica, because this will ruin the instrument. For a basic cleaning, read on.
Wipe the mouthpiece with a damp cloth after playing, or dribble water over it with the holes facing down. Do not let any water go inside the holes. Wiping the mouthpiece with an alcohol wipe will disinfect the outside surface.
Dry it immediately. Don't put it away damp.
Don't play your harmonica during or after eating, and brush your teeth before playing. Run a little water over the mouthpiece, holding it face down under the water, and wipe it dry after playing it each time.