Thank-you so much for your enquiry, this is an excellent question. I would say that it is very risky for anyone to guarantee you 100% permanent hair removal. I would say that with some of the amazing lasers out there, such as the Cutera Laser System (they make use of an ND Yag Laser for hair removal) can definitely guarantee you permanent hair REDUCTION, and most clients are very fortunate and have full removal.
There are some clients who have an odd hair left behind. However, you must understand that any big changes in hormonal activity, such as pregnancy, going into menopause, polycystic ovarian syndrome etc, can all cause NEW hair growth. So we cannot stop the body from activating new follicles. In general though, most clients have very good with Laser Hair Removal treatments.