When is the earliest I can use hair concealer fiber like Caboki/Toppik after hair transplant surgery?

I recommend patients wait until 3-5 days to begin to use Caboki or Toppik on the scabs, remembering to be gentle with hair washing is effect. Ideally you should wait until all the scabs are off so you can clean your scalp well when washing without fear of disturbing the grafts.

I would ask the hair restoration surgeon who performed your procedure for his/her recommendations. Typically I allow my patients to use hair fibers no earlier than 7 days after a transplant.