Safe donor area. The safe donor area describes an area at the back and sides of the head, roughly in the shape of an arc, in which the native hairs are impervious to the affects of DHT, the hormone that causes hair loss. This fact is the basis of follicular unit hair transplants. Follicles removed from the donor area are transplanted to where they are needed. A hair transplant doctor can safely remove hair from this area for transplantation elsewhere. Doctors will not harvest hair outside of the safe donor zone because those hairs are succeptible to DHT. Each patient's donor zone will vary slightly in size and shape because of individual genetics.