Chapter 4: Lasers and Light Devices for Hair Removal

INTRODUCTION

The achievement of permanent or semipermanent hair removal has been a goal for over a century. As early as the 19th century, physicians have attempted to achieve permanent hair removal with employment of electrolysis, initially for the treatment of trichiasis.¹ With the development of laser technology, the field of hair epilation has vastly expanded in recent years. Laser hair removal (LHR) has revolutionized the field of hair removal in large part due to the ability to selectively target and destroy hair follicles, leading to more long-lasting hair removal, requiring less operator dependency, and decreasing the potential side effects compared with other methods of hair removal. However, despite these advantages, it is of paramount importance for safe, effective LHR that the laser/light device operator has a basic understanding of laser–skin interactions including proper patient/laser selection as well as an understanding of hair anatomy, growth, and physiology.

THE HISTORY OF LASER HAIR REMOVAL

The earliest anecdotal evidence of hair destruction by laser light was by Goldman et al who first described ruby laser injury to pigmented hair follicles in 1964.² Later observations of hair loss were made as an indirect side effect during treatment of tattoos and nevi with quality-switched (QS) 694-nm ruby lasers. Lasers were initially used with the target goal of hair removal in the field of ophthalmology and urology for the treatment of trichiasis and urethral grafts.^3–5 The lasers utilized for these early treatments did not specifically target the hair follicles.

The theory of selective photothermolysis, introduced by Anderson and Parrish in 1983, revolutionized the field of lasers with the concept of selectively targeting a particular chromophore based on its absorption spectra and size.⁶ In selective photothermolysis, energy is delivered at a wavelength well absorbed by the target, within a time period less than or equal to the thermal relaxation time of the target. Based on this theory, Grossman et al began the search for a means to specifically eliminate hair utilizing light energy. They selectively targeted melanin in hair follicles using normal-mode, long-pulsed ruby lasers to achieve long-term hair removal.⁷ The preliminary studies with the ruby laser on hair follicles revealed the ability to induce a growth delay and permanent hair removal in some individuals. These early results opened a flood gate of research into the study of various wavelengths and a more in-depth look at laser–tissue interactions in the pursuit of long-term hair removal utilizing lasers and light devices.^7–10

Since the introduction of the first Food and Drug Administration (FDA)–approved hair removal laser system in 1996, the field of laser-assisted hair removal has grown tremendously. Currently, multiple lasers and light sources are available and marketed for the treatment of unwanted or excessive hair in both a clinical environment and, more recently, the home setting. The goals of ideal laser epilation are for the treatment to be practical and ...