You can wear a hard hat the day of and after your hair transplant. It depends which area of scalp has been transplanted. Our patients get a baseball hat as part of their post op kit from the office that they can wear and go home with. If we restore the temporal points, we may not use a hat for the first 4 days. After day 4 anyone can use a hat even if it couches the transplanted area. For more of how to take care of your transplanted hair after your hair restoration procedure check this page:
In answering your question, we typically tell patients to wait until atleast 8 to 10 days post Hair Restoration procedure, before they wear any form of hats. Just make sure it does not touch the recipient region, and allow it to breath every so often. Hope this helps.