What the humidity does to the complete instrument I explain perhaps later! What it, however, causes at your metal parts is well obvious: Corrosion! And I tell you: one likes to carry his guitar home after every rehearsal when he had to replace a complete hardware sentence for his guitar once.
Who does think now it would be done, is mistaken with that! You should fetch your guitar from the bag or the suitcase at home and putting to the fresh air, please. Because, in the suitcase, the guitar can sweat as well as in the rehearsal room!
I don’t want to you make you believe that you all have to buy a desiccator now! All you have to follow is a rule of thumb: Do not exposes your instrument to any conditions you wouldn’t feel yourselves well in these! Nothing more then can go wrong actually!