 Electrolysis is the only permanent hair removal for lighter, finer hair. For darker hair, laser is also permanent and much more efficient.
The FDA defines both laser and electrolysis as permanent treatments. Laser is defined as hair 'permanent reduction', while electrolysis is defined as 'permanent hair removal'. Because laser targets coarse, dark hairs, it may be considered a reduction if lighter, finer hairs are also present in the area. This may be critical in facial areas where fine coarse and fine hair are mixed. However, in legs or bikini lines the fine hair is not an issue so laser can be 100% efftective.
The Illusion of impermanence
Even after an area has been completed with electrolysis or laser, hormonally stimulated hair growth can occur later. New hair growth is uncommon on most body areas after puberty, so you can expect long-lasting results. Facial hair on women or back hair on men, may be stimulated by various factors over time, particularly aging. When this happens after any treatment is complete, it can give the impression that results were only temporary.
There are also situations where hair does not respond to treatment. Hair follicles that lack sufficient melanin may initially seem to respond to laser but can regrow later. Similarly, with electrolysis, regrowth may occur if the hair has been under-treated.