Specificity of laser hair removal using long and short pulses

Abstract

In the present work it has been shown that long single pulses and a series of short pulses with the same exposure duration and total energy density heat the dermal papilla and the bulge area differently. A series of short pulses produces more heat in the papilla what makes temporal hair removal more efficient. Exposure to long single impulses causes a more pronounced heating of the bulge area what provides better long-term effectiveness of epilation.

Purpose. To develop an algorithm for selecting optimal parameters of diode laser irradiation so as to achieve the required temperature level for thermal destruction of the dermal papilla and the bulge area during epilation with long pulses and a series of short pulses.

Material and methods. Epilation with long pulses was performed in 109 patients aged 20–80 having thick black and dark brown hair. The researchers took into account the depth of hair follicle location, Fitzpatrick skin phototype, patient’s age. Epilation was performed with Capello diode laser (wavelength 808 nm) manufactured by Promoitalia Ltd. (Italy). Parameters of energy density and pulse duration for hair removal were selected using the developed tables to determine the heating intensity of dermal papilla of black hair with its depth of 3.5–4.5 mm (fair skin). Pulse duration was 60–150 ms, energy density was 60–120 J /cm².

Results. After 7–9 sessions of thick black hair removal on the shin, thigh, armpits, chin, shoulder and forearm as well as on the pubic area, control examination in half a year and in one year detected only isolated hairs (not more than 1%) in all treated zones.

Conclusion. The developed tables can be used to determine optimal parameters (exposure duration and energy density) for a single impulse in order to achieve necessary temperature level to get thermal destruction of both dermal papilla and bulge area in patients with thick black hair and depth of 3.5–4.5 mm.