October 20 (HealthDay News) -- Laser therapies to remove unwanted hair may be safer and more effective when used separately rather than in combination, according to an Iranian study.

The researchers at the Baqiyatallah University of Medical Sciences in Tehran compared the removal of hair on the legs of 15 people using either long-pulsed 755-nanometer alexandrite lasers (12- and 18-millimeter spot sizes), long-pulsed 1,064 nanometer Nd:YAG laser (12-millimeter spot size), or a combination of alexandrite and Nd:YAG 12-millimeter spot size lasers.

The participants received a total of four treatment sessions at eight-week intervals. Average hair density was measured with a hair counting device and special software, and hair reduction was assessed by comparing digital photographs taken before treatment and at eight- and 18-month follow-up sessions.

Average hair reductions 18 months after final treatment were 75.9 percent for the 12-millimeter spot size alexandrite laser, 84.3 percent for the 18-millimeter spot size alexandrite laser, 73.6 percent for the Nd:YAG laser, and 77.8 percent for the combination therapy.

Leg areas that received the alexandrite laser treatments had higher average pain severity than those treated with the Nd:YAG laser. The highest amount of pain occurred in areas that received the combination treatment. Those areas were also most likely to have hyperpigmentation (dark spots on the skin).

"Despite other studies showing more efficacy of the alexandrite rather than the Nd:YAG laser, our trial results showed no significant difference between them," the study authors concluded. "The use of alexandrite or Nd:YAG laser systems alone for at least four treatments sessions and with eight-week intervals have long-term persistent efficacy in hair reduction with acceptable and transient adverse effects."

The study was published in the October issue of the Archives of Dermatology.

SOURCE: JAMA/Archives journals, news release, Oct. 20, 2008