The ability of lasers to nonspecifically damage hair follicles was noted nearly 50 years ago in the first reports on the use of lasers on human skin.1,2 It was not until the theory of selective photothermolysis was proposed by Rox Anderson and John Parrish at the Wellman Center for Photomedicine at Harvard Medical School, however, that the concept of selectively targeting a particular chromophore based on its absorption spectrum and size was realized.3 Several years later, this group also reported one of the first successful uses of a normal-mode ruby laser for long-term and permanent hair removal.4,5
Today, removing unwanted body hair is a worldwide trend, and photoepilation by laser or other light-based technology is one of the most highly requested procedures in cosmetic dermatology.6 Alternative methods for removing unwanted hair include bleaching, plucking, shaving, waxing, and chemical depilatories. Threading is a common practice in some cultures. Unfortunately, these methods do not provide a permanent solution to unwanted hair, and can be inconvenient and tedious.7,8 Electrolysis is a method for hair removal in which a fine needle is inserted deep into the hair follicle and uses electrical current, thereby destroying the hair follicle and allowing for permanent hair removal of all types of hair.9,10 However, this technique is extremely operator dependent and efficacy in achieving permanent hair removal is variable among patients.9,10 It is also impractical in terms of treating large areas. Eflornithine is a topical inhibitor of ornithine decarboxylase that slows the rate of hair growth, which can be effective for decreasing unwanted facial hair,8 and is currently indicated for the removal of unwanted facial hair in women. Eflornithine can be combined with lasers and intense pulsed light (IPL) for hair removal.11,12 In this chapter, we provide a detailed overview of laser hair removal (LHR) including a discussion of hair follicle biology, the science behind LHR, key factors in optimizing treatment, and future directions.
The hair follicle is a complex, hormonally active structure with a programmed growth pattern (Fig. 53-1). It is anatomically divided into the infundibulum (hair follicle orifice to insertion of the sebaceous gland), isthmus (insertion of the sebaceous gland to the insertion of the arrector pili muscle), and inferior (insertion of the arrector pili to the base of the hair follicle) segments. The dermal papilla, a neurovascular structure that supplies the cells of the proliferating matrix at the base of the follicle, helps form the hair shaft.
Hair follicle anatomy. (Reproduced with permission from Tsao SS, Hruza GJ. Laser hair removal. In: Robinson JK, Hanke CW, Sengelmann RD, Siegel DM, eds. Surgery of the Skin. Philadelphia, PA: Elsevier Mosby; 2005:575–588. Copyright Elsevier.)
Each hair follicle consists of a permanent (upper) and nonpermanent (lower) ...