Race/Class Question

[daisygoth]

I know you can't turn Race or Class cards sideways and that you can discard it at any time. However, can you take it from in play and put it back into your hand to change your Race/Class or do you have to discard it to play another Race/Class? (IE could I go back and forth between a Dwarf and Elf if I wanted to? Or after one is in play would it need to be discarded to go to the next?) Thanks!