Ruby lasers for hair removal were approved by FDA and came into the market in the U.S. in 1997. Ruby lasers have the best published documentation of results. There are also two perfect papers by practitioners which describe optimizing treatment parameters. Studies with short-term follow-up showed 20% to 60% reduction at 3 months. Another found that there is a fluence-dependent relationship at a range of 38% to 49% reduction at 3 months, which can be compared favorably to electrolysis and waxing. A large short-term research observed that about two-thirds of subjects had over 50% reduction at 3 months.
 Long-term observation with ruby is better documented than other lasers. As discussed in the section on “permanent hair reduction,” the pilot research observed 4 of 13 patients had 42% to 60% reduction at 24 months. Several studies since then have also found a great number of non-responders among “ideal” subjects, reasons of that fact are unknown. Two well-designed studies showed almost identical non-response rates of 29% and 28%. Patients had apparently permanent reduction in hair color and diameter, and one observed 22% reduction 7 months after a single treatment. Another investigation had similar results of less than 25% reduction at 6 months after an average of 2 treatments. Other researches have fixed better results: One found 61% reduction at 9 months after 4 treatments. The second noted the sparse regrowth in 63% of patients at 8 months.
 Side effects are generally rare. Usually skin discoloration and darkening are observed. Skin discoloration rates have been reported from 1% to 10%. Darkening is more common and often takes several months to decide. Histological results show that people with darker skin are more likely to have side effects, especially hypopigmentation.
Some ways to reduce side effects such as preheating or precooling the skin before treatment are used. Epidermal cooling is used to reduce pain and side effects, especially in darker skin. Four types of cooling have been developed:
- Clear gel: usually chilled
- Contact cooling: through a window cooled by circulating water
- Cryogen spray: immediately before/after the laser pulse
- Air cooling: forced cold air at -34 degrees C
It was observed that lower fluences cause higher rates of double hairs as regrowth. As with electrolysis, there is a chance of isomorphic phenomena like trauma-induced lesions. Clients should avoid sun after treatment, which can cause significant and persistent pigment changes to the skin lasting several months.
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