Permanent hair removal with a diode-pumped Nd:YAG laser: a pilot study using the direct insertion method

Abstract

Background: The removal of unwanted hair with various laser systems and related procedures has been investigated for many years. All researchers have met difficulty when trying to achieve "permanent" hair removal. In addition, damage to the epidermis and other complications, including hyper- or hypopigmentation in pigmented skin, have occurred because the laser energy was applied indirectly to the hair bulb through the epidermis.

Objective: To achieve permanent hair removal with the use of a diode-pumped neodymium:yttrium-aluminum-garnet laser system with an insulated optical needle. Also, to establish laser treatment parameters that allow for quick and effective removal of hair with minimal pain and no long-term medical complications.

Method: The laser used in the study was capable of producing up to 500 mJ of energy per burst at a 1,064-nm wavelength. A pulse width of 200-500 micros and a burst frequency of 100-200 Hz could be selected, and both defined a subset of the treatment parameter space. An optical needle, typically 130 microm in diameter, was prepared before each new treatment was conducted. Three bursts of energy, 300 mJ each, with a 300-millisecond interval, were delivered through the optical needle into each hair follicle. Between 200 and 300 shin hairs, typically terminal hairs, on each of 5 volunteers were treated. These volunteers were observed over 18.5-30 months for the regrowth of hairs by hair count.

Results: At the end of the observation period (6-30 months after the last treatment), 3 of 5 volunteers showed permanent loss of 76%-94.3% of their unwanted hair. One volunteer lost 34.8% of the original hair, but regrown hair was much thinner than the original terminal hair. One volunteer lost only 22.8% of the original hair, and regrown hair was coarse terminal hair. Except for the loss of hair, no change in skin texture, sensation, or skin color was observed.

Conclusion: The direct insertion optical method (DIOM), delivering laser energy directly to the hair bulb through an optical needle, has proven to be effective and achieves permanent hair removal in 60% of volunteers without medical complications.