Avoiding Blisters From Karate?

I've been taking Shotokan cl for about 4 months now, I go to cl 3 times a week for an hour and a half. Ive noticed my feet becoming more rough and at time hurt the next day. Ive also noticed I get blister allot, sometimes the blisters look like they are healing, but as soon as I go to cl it either opens or another blister forms on top the the healed skin. We train barefoot on the wood floors, dance studio type floors. Ive tried using athletics tape and does not work, the tape sticks on for a while but then gets loose. Is there something I an use or do make my feet more tolerant and not form blisters ?