Well, I shave my face every day, not sure why they'd ask you to grow it out. On the day of the laser treatment, the closer the shave, the better.
I saw results almost instantly. After the second session I noticed I still had some brown hairs on the underside of my chin, but now I barely notice any. I have a rather substantial amount of blonde facial hair though, which makes me sad...
Usually it is recommended to go 6-8 weeks between sessions. 10 sessions sounds about right. That would be closer to 18 months though. You will see most of the results early on, but you have to keep doing it to get the stragglers.
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