This is a common question and we hear a lot of discussions among practitioners about what laser is best for large areas, like legs or a man’s back. We have reviewed several studies published in the last few years, and here is the consensus among our medical panel members.
For individuals with fair skin types I-III each laser will provide good long term results, i.e. 75-80% permanent hair reduction. The 755-nm alexandrite laser is significantly more painful and it is not unlikely that some individuals, especially men, will quit after the 5th treatment, thus potentially reducing the overall efficacy of the treatment.
Alexandrite (755 nm) is not recommended for skin types IV-VI due to the high level of the absorption of this wavelength by the malanin of the skin. Overheating typically results in dispigmentation or scarring of the dark skin. This laser should not be used on tanned skin for the same reason. Nd:YAG 1064 nm laser is the golden standard for hair reduction on dark and tanned skin.
We have reviewed a sizable body of research to answer this question. Yes, these lasers can be used in combination.
Several randomized, single-center, within-participant, investigator-blinded, active-controlled clinical trials have been cmpleted with individuals aged 16 to 50 years with skin phototypes III and IV. These are the only two skin types, which could benefit from a combination treatment. Typical results are: the mean hair reduction 18 months after the last treatment, as measured by the assessors from digital photographs, are 75-82% for alexandrite laser, 74-80% for the Nd:YAG laser, and 77-80% for the combination therapy. The incidence of adverse effects (hyperpigmentation) and pain severity were significantly greater in areas that received combination therapy.
The conclusion is what the majority of practitioners already know: do not use alexandrite lasers for skin types darker than III; Nd:YAG lasers are good for all skin types and tanned skin; combination therapy does not have any additional benefit and may cause more adverse effects.