Because of the difficulty in controlling permanent marker ink that has been dissolved with alcohol, don't use alcohol unless you want to erase EVERY BIT of label text. Otherwise you'll be trying to remember text to re-enter.

However, alcohol can be useful if you have labels that are full of obsolete text. Just put a few drops on a tissue or pad and wipe away as shown in the photo above. Hint: 99% alcohol is generally better than 70% rubbing alcohol.