Please to not clean your harmonica with alcohol
Alcohol will wear down the tips of the tines of my combs but there are a few other reasons not to use it as part of harmonica maintenance.
I spent a big part of my career working in an operating room or ICU as a Respiratory Therapist and Clinical Perfusionist. I'm familiar with asepsis and sterile techniques. Here's my take on cleaning versus trying to kill microorganisms in the harmonica.
While 70 per cent alcohol is effective at cleaning off thermometers and stethoscopes, it is not idea for disinfecting a harmonica. Alcohol is very volatile and evaporates quickly - anything less than 70 per cent concentration will not be effective. And if sprayed as a mist (for example, Mi-T-Mist), you cannot assure that a high enough concentration of alcohol will actually reach the target since most of it will evaporate in transit.
There are too many nooks and crannies in a harmonica for alcohol to work. Not to mention a porous comb will shelter microorganisms from some products.
Alcohol will not kill organisms caught under debris so to reach all the bugs, each piece of the harp must be cleaned first. But if you clean the harp well, there is no real need to sterilize.
I only think about sterilizing a harp if I am worried about a specific pathogen, example someone with active cold sores played my harp.
Instead, I recommend soap and water. My combs do not swell. You can dunk the whole harp with my comb under soapy water and slosh it around. Rinse it out, tap out the excess water and let it dry. You can use a hair dryer to warm up the inside of the harp to dry it out faster.
If you need to disinfect in addition to cleaning, I recommend hydrogen peroxide. It is inexpensive, non-toxic and earth-friendly: it breaks down into oxygen and water.