This question already has an answer here:
My main problem when bouldering and sometimes while climbing is, that after some time the skin/flesh of my middle and lower phalanges start to hurt and the skin comes off so further climbing becomes nearly impossible. The timespan until this happens differes and I can't see any progression over time or that bigger timespans between my climbing sessions would lead to better conditions. It seems to me that this isn't a problem of training, but of poor preparation/condition which lead to a bad form of the day for my fingers.
So my question would be, is there anything I can do between the days of climbing to strengthen and prepare my finger skin/flesh to make it last longer?