The general opinion is that laser hair removal is permanent, and the Food and Drug Administration approved it as “permanent reduction,” but doesn’t work on everyone. Generally, this means that you shouldn’t expect laser to remove every single hair from an area. Most people need to follow up with electrolysis treatments for any remaining hairs for complete clearance as hair becomes too fine for laser to target and you reach diminishing returns. Most will also need touch-up treatments 1-2 times a year after the initial set of treatments for any new growth your body develops with age.
It has also been observed that some people seem to be non-responders – this is not confirmed and reasons are not known as not enough research has been done in this area. Keep in mind that it's also difficult to judge whether someone’s lack of results is due to the person’s potential underlying medical condition that causes continuous growth and makes it seem like laser isn’t working, whether the treatment wasn't performed properly, or whether for some people it just doesn't work and we don't know why. Basically, you can’t determine this for yourself unless you try it. In addition, results also depend on many variables involved, including the tech's experience, type of laser used and how settings are set, etc.
A set of at least 6-8 treatments at specified intervals are generally necessary to achieve substantial hair removal with laser. Factors that determine the length of treatment include the particular area to be treated, the texture of hair, frequency of treatments, history of temporary measures to remove hair (waxing, tweezing, shaving, and depilatories, etc.) etc.
Electrolysis is considered a permanent hair removal method that has been used for the past 125 years. It involves treating one hair at a time and can take a considerably long time to complete a large area, but IS an option as well. It is also the recommended method for small areas (generally, chin, upper lip, eyebrows, etc), as well as for fine and light-colored hair. The most cost-efficient treatments to completely clear an area should start with laser to remove the bulk of the hair and finish with electrolysis to remove the remaining finer sparse hair.