The following information was taken from http://www.hairfacts.com/medpubs/ndyagmed.html

Nd:YAG laser using a carbon-based lotion was promoted as long-term and even permanent for years, until published clinical data showed that this was not true. [1] The best overview of Nd:YAG history, benefits and limitations is Littler's 1999 article. [2]

Q-switched with carbon-based lotion

Early published medical papers using Nd:YAG with the carbon lotion reported from 27% to 66% reduction at 3 months after one treatment. [3] One 15-subject study found long pulse Nd:YAG more effective and less painful when compared to alexandrite treatment [4]

One large study of patient satisfaction at six months after multiple treatments showed those seeking to thin hair were generally pleased, but 75% of those expecting more were not pleased. [5] One study observed full regrowth by month six [6]. Side effects were observed in one study to be less likely with this treatment compared to other lasers. [7] Another also saw fewer side effects than ruby or alexandrite [5]

One study confirms observation that treatment is probably more effective on anagen hairs. [8] Histological evidence suggests thermal damage occurs to about 1 mm deep. [9]

One small study suggests promise for treatment of “shaving bumps” (pseudofolliculitis barbae) [10] and another reports on successful treatment of infants born with excessive amounts of downy hair (hypertrichosis lanuginosa congenita) [11]

Long pulse Nd:YAG

The one published study found 15 subjects had 59% reduction at 3 months [12]

An unpublished report observed skin discoloration in tanned skin is rare and resolved by 6 months. Eleven patients followed had about 30% reduction at 6 months. [13] Another unpublished manufacturer report [14] with a long-term follow up [15] observed that 25 subjects had median of 27% reduction at 3 months after a single treatment. Also in this report, observers of before and after photos thought the after photos looked better in three-fourths of the treated areas, with the control looking better in half the treated areas. Sites receiving one or two treatments were observed to have 39% and 50% reduction at 12 months, respectively.

References

1. Please see hairfacts.com for a list of Nd: YAG laser medical data.
2. Littler CM. Hair removal using the Nd:YAG laser system. Dermatologic Clinics 1999 Apr;17(2):401-30, x.
3. Goldberg DJ, Littler CM, Wheeland RG. Topical suspension-assisted Q-switched Nd:YAG laser hair removal. Dermatologic Surgery 1997 Sep;23(9):741-5.
4. 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):844-47; discussion 848-50.
5. Bencini PL, Luci A, Galimberti M, Ferranti G. Long-term epilation with long-pulsed neodimium:YAG laser. Dermatologic Surgery1999 Mar;25(3):175-8.
6. Nanni CA, Alster TS. Optimizing treatment parameters for hair removal using a topical carbon-based solution and 1064-nm Q-switched neodymium:YAG laser energy. Archives of Dermatology 1997 Dec;133(12):1546-9.
7. 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.
8. Kolinko VG, Littler CM, Cole A. Influence of the anagen:telogen ratio on Q-switched Nd:YAG laser hair removal efficacy. Lasers in Surgery and Medicine 2000;26(1):33-40.
9. Goldberg DJ, Silapunt S. Histologic evaluation of a millisecond Nd:YAG laser for hair removal. Lasers in Surgery and Medicine 2001;28(2):159-61.
10. Rogers CJ, Glaser DA. Treatment of pseudofolliculitis barbae using the Q-switched Nd:YAG laser with topical carbon suspension. Dermatologic Surgery 2000 Aug;26(8):737-42.
11. Littler CM. Laser hair removal in a patient with hypertrichosis lanuginosa congenita. Dermatologic Surgery 1997 Aug;23(8):705-7.
12. Goldberg DJ, Samady JA. Evaluation of a long-pulse Q-switched Nd:YAG laser for hair removal. Dermatologic Surgery 2000 Feb;26(2):109-13.
13. Grossman M. Hair Removal for Tanned Patients & Wide Range of Skin Types with the Altus Nd:YAG CoolGlide Laser – Study Results (unpublished 11/2000)
14. Kilmer SL. 3 Month Clinical Results Using the CoolGlide Long-Pulse Nd:YAG Laser for Hair Removal. (unpublished and undated)
15. Kilmer SL. Summary of 15 Month Clinical Results Using the CoolGlide Long-Pulse Nd:YAG Laser for Hair Removal. (unpublished, June, 2000)