Alexandrite laser medical data
Alexandrite lasers for hair removal were cleared by FDA to market in the U.S. in 1997. Despite its current popularity, there’s not a lot of data on alexandrites for hair removal.  Arguably the best overview is Ash. 
A short-term study of 130 female subjects had an average of 8 facial treatments over 18 months. Researchers observed an average 75% reduction for dark hair at 3 months and 10% for light hair. A similar study noted 81% to 95% reduction at 3 months after 3 to 5 treatments,  as did a smaller study which observed 86% reduction at 3 months after a single treatment.  One comparative study observed 74% reduction at 3 months after 4 treatments, which was about twice the clearance they observed with electrolysis.  Another with short term follow-up observed 19% reduction at 3 months, which compared favorably to Nd:YAG. 
A mid-range study observed 25-47% reduction at 4 to 6 months after 1 or 2 treatments in various areas.  A similar study found 66% reduction at 1 month, 27% reduction at 3 months, and 4% reduction at 6 months. 
One study of treatment at the bikini found an average of 43% reduction at 6 months plus “one growth cycle” after a single treatment, with 60% of sites having greater than 30%.  Another study with five bikini treatments observed 78% reduction at 12 months after final treatment.  One study comparing long and short pulsewidths observed about 33% reduction at 6 months for both pulsewidths.  This was also observed in a study observing 60% to 80% reduction at 6 months after 3 treatments.  Damage to follicles was confirmed in one thorough histological analysis. 
In 150 dark-skinned patients (skin type IV-VI) treated with alexandrite side effects occurred in about 2% of cases.  This matches results in a large-scale study of lighter skin types.  Preheating or precooling the skin before treatment may help reduce side effects. [17, 18] Lower fluences have been observed to cause higher rates of double hairs as regrowth. 
- Please see summary below.
- Ash K, Lord J, Newman J, McDaniel DH. Hair removal using a long-pulsed alexandrite laser. Dermatologic Clinics. 1999 Apr;17(2):387-99, ix.
- Raulin C, Greve B. Temporary hair loss using the long-pulsed alexandrite laser at 20 milliseconds. European Journal of Dermatology. 2000 Mar;10(2):103-6.
- Finkel B, Eliezri YD, Waldman A, Slatkine M. Pulsed alexandrite laser technology for noninvasive hair removal. Journal of Clinical Laser Medicine and Surgery. 1997;15(5):225-9.
- Connolly CS, Paolini L. Study reveals successful removal of unwanted hair with LPIR laser. Cosmetic Dermatology 1997;10:38-40.
- Gorgu M, Aslan G, Akoz T, Erdogan B. Comparison of alexandrite laser and electrolysis for hair removal. Dermatologic Surgery. 2000 Jan;26(1):37-41.
- Rogers CJ, Glaser DA, Siegfried EC, Walsh PM. Hair removal using topical suspension-assisted Q-switched Nd:YAG and long-pulsed alexandrite lasers: A comparative study. Dermatologic Surgery. 1999 Nov;25(11):844-4; discussion 848-50.
- McDaniel DH, Lord J, Ash K, Newman J, Zukowski M. Laser hair removal: a review and report on the use of the long-pulsed alexandrite laser for hair reduction of the upper lip, leg, back, and bikini region. Dermatologic Surgery. 1999 Jun;25(6):425-30.
- Nanni CA, Alster TS. Long-pulsed alexandrite laser-assisted hair removal at 5, 10, and 20 millisecond pulse durations. Lasers in Surgery and Medicine. 1999;24(5):332-7.
- Laughlin SA, Dudley DK. Long-term Hair removal using a 3-millesecond alexandrite laser. Journal of Cutaneous Medicine and Surgery. 2000 Apr;4(2):83-88.
- Lloyd JR, Mirkov M. Long-term evaluation of the long-pulsed alexandrite laser for the removal of bikini hair at shortened treatment intervals. Dermatologic Surgery. 2000 Jul;26(7):633-7.
- Goldberg DJ, Ahkami R. Evaluation comparing multiple treatments with a 2-msec and 10-msec alexandrite laser for hair removal. Lasers in Surgery and Medicine. 1999;25(3):223-8.
- Boss WK Jr, Usal H, Thompson RC, Fiorillo MA. A comparison of the long-pulse and short-pulse Alexandrite laser hair removal systems. Annals of Plastic Surgery. 1999 Apr;42(4):381-4.
- Ono I, Tateshita T. Histopathological changes in the hair follicle after irradiation of long-pulse alexandrite laser equipped with a cooling device. European Journal of Dermatology. 2000 Jul-Aug;10(5):373-8.
- Garcia C, Alamoudi H, Nakib M, Zimmo S. Alexandrite laser hair removal is safe for Fitzpatrick skin types IV-VI. Dermatologic Surgery. 2000 Feb;26(2):130-4.
- Nanni CA, Alster TS. Laser-assisted hair removal: side effects of Q-switched Nd:YAG, long-pulsed ruby, and alexandrite lasers. Journal of the American Academy of Dermatology. 1999 Aug;41(2 Pt 1):165-71.
- Topping A, Gault D, Grobbelaar A, Green C, Sanders R, Sibbons P, Linge C. Successful reduction in skin damage resulting from exposure to the normal-mode ruby laser in an animal model. British Journal of Plastic Surgery 2001 Mar;54(2):144-150.
- Raulin C, Greve B, Hammes S. Cold air in laser therapy: first experiences with a new cooling system. Lasers in Surgery and Medicine 2000;27(5):404-10.
- Ye JN, Prasad A, Trivedi P, Knapp DP, Chu P, Edelstein LM. Pili bigeminy induced by low fluence therapy with hair removal alexandrite and ruby lasers. Dermatologic Surgery 1999 Dec;25(12):969.
Summary of data with links to abstracts
= recommended only for in-depth researchers
= may be worth ordering
= strongly recommended
Human clinical studies
Connolly (1997): An early article showing 20 subjects had 86% reduction three months after a single treatment.
Finkel (1997): Finkel took before and after photographs of 126 fair- to dark-haired subjects who had 3 to 5 treatments on various areas. Observers of the photos noted 81% to 95% reduction 3 months after last treatment.
Fuchs (1997): an clinical early report of success.
Boss (1999): 18 subjects in full skin type range had treatment in various areas to compare long pulse and short pulse. Six months after 3 treatments, they report 60% to 80% reduction.
McDaniel (1999): 22 ideal subjects (light skin, dark hair) had 25-47% reduction at 4 to 6 months after 1 or 2 treatments in various areas.
Nanni (1999): 36 subjects had one treatment. Hair counts were reduced by 66% at 1 month, 27% at 3 months, and 4% at 6 months.
Goldberg (1999): 14 subjects had 3 treatments on paired sites. 6 months after treatment average reduction was about 34%.
Rogers (1999): 15 subjects had 1 alexandrite treatment on one armpit. 3 months after treatment average reduction was 19%.
Gorgu (2000): 12 subjects had one armpit treated with electrolysis and the other with alexandrite laser. 14 weeks after final treatment, they reported electrolysis had 35% clearance and laser had 74% clearance.
Raulin (2000): 130 female subjects had an average of 8 facial treatments over 18 months. 13 weeks after final treatment, average clearance was 75% for dark hair and 10% for light hair.
Ono (2000): A histopathological study comparing hairs before and after treatment.
Lloyd (2000): 11 subjects had 5 bikini treatments over 15 weeks. 1 year after final treatment, average clearance was 78%
Laughlin (2000): Photos of 25 various body sites getting one treatment were observed to have an average 43% reduction in terminal hairs after "one growth cycle." Counts remained stable 6 months after the growth cycle.
Ye (1999): Reports that low-fluence alexandrite treatment can cause more than one hair to grow from the same follicle (pili bigemini).
Garcia (2000): In 150 dark-skinned patients (skin type IV-VI) treated with alexandrite, about 2% had side effects.
Narukar (1998): Compares long-pulse on various skin types (no abstract).
Ash (1999): A fairly good overview of available data at the time of writing.
Nanni (1998): A practical review of lasers widely available at the time (Nd:YAG, ruby, alexandrite).