Cosmetics Applications of Laser and Light-Based Systems

Gurpreet Ahluwalia

• Publisher: William Andrew
• Year: 2008
• Topic: Business
• eBook ISBN:
  9780815519676
• Subtopic: Industria tessile e della moda
• Index: Business

In recent decades, cosmetic science has found new high-potency, bioactive ingredients that produce visibly superior skin benefits to the consumer. Light-based devices, including lasers and intense-pulsed light systems, have been used for years in the treatment of cutaneous vascular and pigmented lesions, yet have only recently appeared in cosmetic applications, beauty salons and spas. Meanwhile, ever more research and development is being performed with the intent of bringing them to the home-use market. This book is the first to introduce a range of currently used, or under development, laser- and light-based technologies that will provide greater cosmetic benefits to the consumer. It explains the basic physics of light-based technologies, the bio-physical principles behind their mechanism of action, and their applications in many cosmetic procedures. The fundamentals of skin and hair physiology (relevant to the understanding of actions of various cosmetics) are also explained, as are: cosmeceuticals; topical drugs for cosmetic benefits; non-invasive and invasive options available for beauty treatments, and how all this fits in with the emerging light-based technologies. Individual chapters are devoted to the various skin and hair conditions where light-based systems are currently used. Treatments discussed include the rejuvenation and toning of damaged skin; skin resurfacing and microdermabrasion; hair removal and growth reduction; wrinkle reduction; acne treatment and cellulite. Finally, the book examines the synergy of cosmeceuticals and topical bioactive agents with light-based technologies, safety issues, a regulatory perspective for OTC marketing, and concludes with a discussion of the business aspects related to home-use of light-based devices. - The first book to introduce this emerging technology to the personal care industry - Explains their applications in many cosmetic procedures - Devotes individual chapters to common skin and hair conditions

1

Basic Technology and Targets for Light-Based Systems

Chapter 1 The Biology of Hair Growth

Valerie Anne Randall, Natalia V. Botchkareva, Centre of Skin Sciences, School of Life Sciences, University of Bradford, Bradford, UK

• 1.1 Introduction 4
• 1.2 The Functions of Hair 4
• 1.3 Hair Follicle Anatomy 7
  • 1.3.1 The Hair Shaft 7
  • 1.3.2 The Inner Root Sheath 7
  • 1.3.3 The Outer Root Sheath 7
  • 1.3.4 The Dermal Papilla 8
• 1.4 Changing the Hair Produced by a Follicle via the Hair Growth Cycle 9
  • 1.4.1 Telogen-The Resting Phase 10
  • 1.4.2 Anagen-The Growth Phase 11
  • 1.4.3 Catagen-The Regressive Phase 11
  • 1.4.4 Exogen-Hair Shedding 13
• 1.5 Hair Pigmentation 13
• 1.6 Seasonal Changes in Hair Growth 15
  • 1.6.1 Hormonal Coordination of Seasonal Changes in Animals 15
  • 1.6.2 Seasonal Variation in Human Hair Growth 16
• 1.7 Hormonal Regulation of Human Hair Growth 18
  • 1.7.1 Pregnancy 18
  • 1.7.2 Androgens 18
    • 1.7.2.1 Human Hair Follicles Show Paradoxically Different Intrinsic Responses to Androgens 18
    • 1.7.2.2 The Mechanism of Androgen Action in Hair Follicles 21
• 1.8 Treatment of Hair Growth Disorders 25
• References 26

1.1 Introduction

The hair follicle is a highly dynamic organ found only in mammals. Although frequently overlooked, the follicle is fascinating from many viewpoints. For cell and developmental biologists it has an almost unique ability in mammals to regenerate itself, recapitulating many embryonic steps en route [1,2]. For zoologists, it is a mammalian characteristic, significant for their evolutionary success and crucial for the survival of many mammals-loss of fur or faulty colouration leads to death from cold or predation. Human follicles also pose a unique paradox for endocrinologists as the same hormones, androgens, cause stimulation of hair growth in many areas, while simultaneously inhibiting scalp follicles causing balding [3,4]. In contrast, hair is often seen as rather irrelevant medically, as human hair loss is not life threatening. Nevertheless, hair is very important for most people [5]. Many men spend significant time shaving daily and vast amounts are spent on hair products; a ‘bad hair day’ is a common expression for days when everything goes wrong! This reflects the important role hair plays in human communication in both social and sexual contexts and explains why hair disorders such as hirsutism (excessive hair growth) or alopecia (hair loss/balding) cause serious psychological distress [6].

Hair growth is co-ordinated by hormones, usually in parallel to changes in the individual’s age and stage of development or environmental alterations like day-length [7]. Hormones instruct the follicle to undergo appropriate changes so that during the next hair cycle, the new hair produced differs in colour and/or size. This chapter will review the functions of hair, its structure and the processes occurring during the hair growth cycle, the changes which can occur with the seasons, and the importance of the main regulator of human hair growth, the androgens. Throughout the chapter, the main emphasis will be on human hair growth.

1.2 The Functions of Hair

Mammalian skin produces hair everywhere except for the glabrous skin of the lips, palms, and soles. Although obvious in most mammals, human hair growth is so reduced with tiny, virtually colourless vellus hairs in many areas, that we are termed the “naked ape”. Externally hairs are thin, flexible tubes of dead, fully keratinised epithelial cells; they vary in colour, length, diameter, and cross-sectional shape. Inside the skin hairs are part of individual living hair follicles, cylindrical epithelial downgrowths into the dermis and subcutaneous fat, which enlarge at the base into the hair bulb surrounding the mesenchyme-derived dermal papilla (Fig. 1.1) [8].

Figure 1.1 The hair follicle. The right-hand side of this diagram shows a section through the lower hair follicle while the left represents a three-dimensional view cut away to reveal the various layers.

Drawing by Richard J. Dew. Reproduced from Randall [3].

In many mammals, hair’s important roles include insulation for thermoregulation, appropriate colour for camouflage [9], and a protective physical barrier, for example, from ultraviolet light. Follicles also specialise as neuroreceptors (e.g. whiskers) or for sexual communication like the lion’s mane [10]. Human hair’s main functions are protection and communication; it has virtually lost insulation and camouflage roles, although seasonal variation [11–13] and hair erection when cold indicate the evolutionary history. Children’s hairs are mainly protective; eyebrows and eyelashes stop things entering the eyes, while scalp hair probably prevents sunlight, cold, and physical damage to the head and neck [14]. Scalp hair is also important in social communication. Abundant, good-quality hair signals good health, in contrast to sparse, brittle hair indicating starvation or disease [15]. Customs involving head hair spread across many cultures throughout history. Hair removal generally has strong depersonalising roles (e.g. head shaving of prisoners and Christian/Buddhist monks), while long uncut hair has positive connotations like Samson’s strength in the Bible.

Other human hair is involved in sexual communication. Pubic and axillary hair development signals puberty in both sexes [16–18], and sexually mature men exhibit masculinity with visible beard, chest, and upper pubic diamond hair (Fig. 1.2). The beard’s strong signal and its potential involvement in a display of threatening behaviour, like the lion’s mane, [5,10,14] may explain its common removal in “Westernised” countries. This important communication role explains the serious psychological consequences and impact on quality of life seen in hair disorders like hirsutism, excessive male pattern hair growth in women, and hair loss, such as alopecia areata, an autoimmune disease affecting both sexes [19]. Common balding, androgenetic alopecia or male pattern hair loss [20], also causes negative, effects, even among men who have never sought medica...

Table of contents

• Cover
• Title Page
• Personal Care and Cosmetic Technology
• Copyright
• Dedication
• Table of Contents
• Contributors
• Preface
• Part 1- Basic Technology and Targets for Light-Based Systems
• Part 2 - Hair Management by Light-Based Technologies
• Part 3 - Light-Based Systems for Improving Skin Appearance
• Part 4 - Treatment of Skin and Hair Disorders Using Light-Based Technologies
• Part 5 - Synergy of Bioactive Molecules with Light Energy
• Part 6 - Regulatory and Safety Guidance
• Index
• Personal Care and Cosmetic Technology Series