Sadly I had to learn the hard way. I went to a spa place that did so called "electrolysis". I was told it would take up to a year and it was a dollar a minute. She would grab a hair with a tweezer and after a few seconds/zaps she would be able to remove the hair. Even though it is a less painful way to remove hair, it was not permanent. A few times she would drop the tweezer on me! The tweezer would be hot and a few times hit my upper lip and burned! The last straw for me was when she pressed the tweezer against my upper lip and I pushed her away. When I said she burned me, she looked at her tweezer with confusion. The last appointment that I was suppose to go to, I overslept and missed the appointment. Thank god.
I finally found a real electrologist and for 2 years on and off, she did my entire upper lip (to this day i have a few very light strands) and my underarm (I have a few strands). I even had a strand of hair that showed up on a strange spot on my chest, and kept reappearing. For a year, I kept plucking it and my skin kept getting irritated. One day I mentioned it to her, and as she was removing, she found two hairs! The hairs have not appeared to this day.
BTW the hairs that were removed from the tweezer process came back. Go figure.