What causes hairiness in threads?

Check working condition and parts of sewing machines (i.e. hook, bobbin case, throat plate, needle tip, sharp thread guide) plus thread quality and material thickness.

I have untwisted thread, why is this and how can I prevent it?

How do I minimise hairiness effect after stitching using CFP or any unbonded threads?

Check thread-needle size compatibility and needle condition. Check components in contact with thread (thread path, tension discs, needle eye, bobbin, rotary hook) and also machine timing.