Properly done electrolysis completely kills the stem cells at the root of the hair, no hair can form again from that root.
The human body is very resilient and new hair follicles can be formed. Without androgens (T), new hairs will remain as small and thin vellus hairs just like genetic females have.
More detail if you want it
The complexity of hair follicles and their development cycle can make achieving a one zap = one kill difficult.
Multiple roots can effectively share the same pore, roots that have had insufficient nutrients can be re-energized as a side-effect of hair removal treatment on nearby hairs, damaged roots can be pointing away from the skin surface making treatment less effective on that root.
Hair growth cycles can make it seem like the process is not working.
The most effective treatment happens when the hair is growing (anagen phase).
When the growing stage ends, the hair bulb detaches from the root, the root becomes dormant while the hair is slowly pushed out until it sheds (this phase can last months).
For effective treatment, the probe needs to be very near the root stem cells when the electric current (or radio frequency burst) is triggered. An electrologist inserts the probe down to the hair bulb by feel, when the hair is not actively growing, the hair bulb is moving away from the root stem cells, thus reducing the effectiveness of the treatment.
The first full clearing of your facial hair can appear like it didn't work well, as only the actively growing hairs were killed. The good news is essentially all of the hairs that appear after than should be in the growth phase and the zap to kill ratio will go way up. Successfully getting rid of a mail beard will take regular sessions every month for many months.
Lasers: Lasers are always less effective than electrolysis. When dealing with terminal hairs, especially male beard hair, some folks achieve a "good-enough" result that allows them to transition quicker and/or get an initial clearing quicker.
-Cindi
