Ashadyna,
I'm afraid I don't have links to studies in English, and can't yet link to even non-English studies until I make a few more hundred posts, so I hope you don't mind reading about what I've myself heard, learnt and experienced.
Used properly, laser can be effective and permanent. The clinic I know (and went to) published a study—including histological data—that indicated that if applied properly even vellus hair can be permanently removed provided that it is not white. The clinic guaranteed permanent beard removal for life for a flat fee of approximately $1000. The caveats were:
- Since hair cycles are irregular, complete removal can take several years.
- Some hair may lose pigment when treated.
- Unpigmented hair is impervious to laser.
According to the doctor in charge:
- For high growth density areas the first treatment fluence must be low enough to just stun the hair roots. This first treatment is meant to just induce shedding and does not permanently remove anything. Its goal is to temporarily lower growth density enough to let the clinic increase the fluence in subsequent sessions without causing skin damage. The second treatment is timed around two to three weeks later to allow for maximum shedding.
- All subsequent sessions must be scheduled so as to keep the hair density low enough to maintain and incrementally increase fluence.
- Sufficient laser tip refrigeration is necessary to prevent heating of non-target tissue. (The tips at the clinic were cooled down to -20°C.）
- The tip pressure must be high to efficiently remove heat from the target spot and to incline the roots so that the light hits them broadside, rather than from just the top.
- Gel must be used to maximize heat transfer.
- The tips must be cleaned frequently (every few shots). Any debris on the glass surface not only lowers the energy delivered to the target, but also heats up as it blocks and absorbs the laser energy. This can cause burns at high fluences.
- The treatment area must be charted for complete coverage during each session (a grid drawn on skin using a color that doesn't react to the laser.)
Provided the above and the right laser for the skin type, hair will be permanently reduced.
Yes, reduced.
From what I understand, the reason laser has to be called "hair reduction" is that it absolutely cannot remove every single hair—at least if some is white. Some will be, and some may also turn white when the roots are damaged.
In contrast, every single hair can be unfailingly removed using proper electrolysis technique.
I've experienced both treatments. Laser did reduce the number of hairs on my face by about 97%. That part cost me just the $1000 that I paid in the beginning. It permanently removed all hair that had any significant color, but since the treatments had to be spaced farther and farther apart to be meaningful it took about three years. Some also turned reddish, and some white. To get rid of the red ones the clinic had to eventually increase the fluence to 42 J/cm2. (I had no skin damage.) The white ones were of course impervious to further treatment.
After the laser I underwent about 15 hours of electrolysis to remove the whites, weed out stragglers hiding within the sideburn border, and take care of other little odds and ends here and there.
To sum up, insufficient fluence will only temporarily stun hair. Even if it does damage the roots, as long as papillae remain viable the hair may come back. (The "bulb" located in the mid-area of the follicle is thought to play a part in this.) A high fluence is very effective, but precautions must be taken and proper technique used to avoid burns.
Electrolysis is slower, but guaranteed to be permanent
if the practitioner is skillful. The quoted 50% regrowth rate that I've also seen only means that there often is something wrong with the insertions and/or power settings used.
As for Anne Lawrence, I'm afraid I cannot comment.
