Using hair fibres and hair concealers after a hair transplant, including overnight use?

At 6 weeks you are well healed and should have no issue using hair fibers. After 7-10 days you should be able to use fibers without causing a problem. You just want to be careful in that initial period (7-10 days)  not to let anything contaminate the graft site.

You can start using concealers few days after surgery. If you are concerned about its use, it is best to ask your surgeon.

This should be fine with no issues at this point post op. The problem with these concealers is the potential for infection or inflammation secondary to irritation. After approximately 2 weeks to be on the safe side should be fine. Take care.  

The usage of hair fibers and concealers has no effect on the success of the hair transplant. 

I tell my patients to hold off until all of the crusts are gone from the recipient area as these fibers can be embedded in the crusts causing possible infection