WO2000024464A1

WO2000024464A1 - Method of hair removal by transcutaneous application of laser light

Info

Publication number: WO2000024464A1
Application number: PCT/CA1998/001005
Authority: WO
Inventors: Bob W. Stewart; Frances R. Jochum
Original assignee: Keralase Ltd
Current assignee: Keralase Ltd
Priority date: 1998-10-28
Filing date: 1998-10-28
Publication date: 2000-05-04
Anticipated expiration: 2001-04-28
Also published as: JP2002528191A; CA2348788A1; EP1124612A1; AU9731498A

Abstract

A method of hair removal, used primarily for cosmetic purposes, comprising the transcutaneous use of laser light having a wavelength which targets the keratin component of hair, thus destroying the air by photothermolysis without damage to surrounding skin or tissue; this primary method may be supplemented by the use of intrafollicular hair removal methods utilizing a second wavelength of light produced by the same source used to generate the primary light wavelength.

Description

Method of Hair Removal by Transcutaneous Application of Laser Light

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to a method of permanent hair removal using laser light. More specifically, the invention relates to the transcutaneous use of laser light to target the keratin component of hair, thus destroying the hair by photothermo lysis without damage to surrounding skin or tissue.

2. Description of the Prior Art

Currently available laser hair removal methods may be classified as either mtrafoUicular or transcutaneous in nature. Intrafollicular methods comprise the delivery of laser light thru a small probe tip to the hair follicle. The light utilized is of a wavelength which is readily absorbed by either the melanin in the hair or the hemoglobin in the blood vessels surrounding the papilla. This absorption of light energy produces heat, resulting in damage to the hair shaft, photocoagulation of the tissue surrounding the papilla, and subsequent destruction of the hair. Because the light energy employed in this method is absorbed by either blood or melanin in the skin, it requires the use of a very narrow beam of light to target a single hair at a time and prevent damage to the surrounding tissue. This results in a painstaking, time-consuming process which must be administered by a skilled operator. When targeting melanin, this method losses effectiveness when used on lighter haired or darker skinned patients. In addition, some methods in this category require that the needle-like probe tip be inserted into the hair follicle, a painful process which must be repeated for every hair.

Transcutaneous laser hair removal methods currently available utilizes a substance which is massaged into the skin to penetrate the hair ducts. After cleaning the substance from, the skin's surface, light of a wavelength which passes through the skin, but which is absorbed by the substance, is directed onto the treated area. The absorption of energy by the substance applied to the hair duct causes photocoagulation of the tissue surrounding the papilla and results in destruction of the hair. Although this method allows for treatment of a sizable area of skin, it requires the inconvenient, time consuming application of the light-absorbing substance. In addition, great care must be taken to completely remove the substance from the skin's surface prior to the laser treatment to avoid damage to the skin.

Because of the disadvantages associated with both methods of hair removal in use today, a new method is needed which provides faster, more convenient, and less painful permanent hair removal without damage to the patient's skin.

SUMMARY OF THE INVENTION

The invention relates to a method of permanent hair removal used primarily for cosmetic purposes. This method comprises the transcutaneous use of laser light having wavelength in the 880-930 nanometer range wherein the light is directed onto an area of skin on which hair removal is desired. Light of this wavelength passes through the skin with only minimal absorption by blood, blood components, and melanin. This wavelength is, however, readily absorbed by the protein keratin, the main component of hair of all colors. Absorption of the light energy by the keratin produces heat, which damages the hair shaft and root and photocoagulates the blood vessels and tissue surrounding the papilla, resulting in destruction of the hair and preventing its re-growth.

In its preferred embodiment, the method also includes the use of a second wavelength of laser light produced by known means, such as second harmonic generation or 3 -mixing plus second harmonic generation, from the same laser source which generates the primary 880-930nm wavelength. This second wavelength of light, which will be in the 440-465 nanometer range, is readily absorbed by both blood components and melanin. An intrafollicular probe is used to deliver the second wavelength of light to the hair follicle, in the manner described in the prior art, to treat the small percentage of hairs having papillas at a skin depth beyond the effective range of the primary wavelength of light. In this fashion, a single laser light source can be used to treat all types of hair in the least painful and most efficient, cost effective, and convenient manner possible.

There are numerous problems associated with the hair removal methods in the field of prior art. Some of these methods are painful for the patient. Others have varying effectiveness depending on the skin and hair color of the patient. Most must be administered by highly skilled operators to reduce the risk to the patient. All of these methods involve expensive, painstaking, and time-consuming processes. In addition, all carry substantial risk of skin damage if not performed properly.

It is an object of the invention to provide a hair removal method which: 1) is fast and convenient; 2) is less painful; 3) is effective on hair of all types; 4) has reduced risk for skin damage; and 5) utilizes a low cost, low maintenance, and low power consumption laser source. Further objects and advantages of the invention will become apparent from a consideration of the drawings and description. BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a sectional view of an area of skin showing the structure of hair and skin and the transcutaneous application of laser light.

Figure 2 is a graph showing the absoφtion spectrum of hemoglobin, melanin, and keratin in the visible and near infra-red light range.

Figure 3 is a sectional view of an area of skin showing the structure of hair and skin and the intrafollicular application of laser light.

DRAWING REFERENCE NUMERALS

9 hair

10 shaft

11 root

12 papilla

13 follicle

14 blood vessels

15 sebaceous glands

16 epidermis

17 dermis

18 laser light

19 fiber optic cable probe tip

20 intrafollicular probe DESCRIPTION OF THE PREFERRED EMBODIMENT Description:

Figure 1 illustrates the preferred embodiment of the invention. As shown, laser light 18 emanates from the probe tip 19 of a fiber optic cable, not shown, and is directed onto the surface of the skin. The other end of the fiber optic cable is connected to a laser light source, also not shown. The size and shape of the light beam may be customized to meet the requirements of any individual application. Figure 1 also illustrates the structure of hairs 9 and the surrounding upper and lower skin layers, known as the epidermis 16 and the dermis 17, respectively. Hair 9 comprises shaft 10, shown shaved near the surface of the skin, and root 11. Follicle 13 is a sac which encloses shaft 10, root 11 and adjacent sebaceous glands 15. Located at the lower end of follicle 13 is the papilla 12, which is fed by blood vessels 14 and provides nourishment to root 11. In order to prevent regrowth of hair 9, it is the papilla 12 and blood vessels 14 which must be damaged sufficiently to prevent continued nourishment of root 11.

Figure 2 illustrates the relatively high absoφtion of light in the 880-930 nm wavelength range by the protein keratin. Figure 2 also shows the relatively low absoφtion of light in the same range by the hemoglobin and melanin present in the tissue surrounding the hair. These absoφtion characteristics of keratin, hemoglobin, and melanin allow the transcutaneous use of light of the chosen wavelength to target the keratin in the hair shaft and subsequently destroy the papilla without damage to the surrounding tissue.

The preferred embodiment of the invention primarily utilizes laser light 18 having wavelength in the 880-930 nanometer range. As indicated in Figure 2, light of this wavelength passes through the dermis 17 and the epidermis 16 with only minimal absoφtion by blood, blood components, and melanin. This wavelength is, however, readily absorbed by the protein keratin, which is the main component of hair of all colors. Absoφtion of the light energy by the keratin produces heat, which damages the hair shaft 10 and root 11. This heat may also photocoagulate the blood vessels 14 feeding the papilla 12, resulting in destruction of the hair 9 and increasing the probability of permanent removal.

Power level and duration of the laser pulse directed onto the skin must be carefully chosen to optimize the conduction of heat from the hair shaft and root to the papilla. As an example, a 0.1 second pulse from a laser delivering a power level of approximately 6 milliwatts per hair to the root would deliver sufficient energy to the hair shaft and root to result in significant damage to the papilla and a high probability of permanent hair removal. Use of a shorter, higher energy laser pulse will rapidly vaporize the hair, resulting in hair removal below the surface with little probability of permanent hair destruction. Pulses of less than 0.0001 seconds in duration having sufficient energy to damage hair can lead to very explosive, i.e. photoacoustic, absoφtion and to hyper- or hypo-pigmentation. Conversely, a pulse longer than 0.2 seconds can result in damage to the surrounding tissue and possible scarring.

Although highly effective on hairs having papillas at a skin depth of 1.0 cm or less, scattering and absoφtion of the laser light make the transcutaneous method less effective on the small percentage of hairs which exceed this limit. To effectively remove these hairs, the preferred embodiment of the invention further comprises the intrafollicular application of laser light 18 having a second wavelength, as shown in Figure 3. This second wavelength is produced by known means, such as second harmonic generation or 3 -mixing plus second harmonic generation, from the same laser source which generates the primary 880-930 nm wavelength. In the manner described in the prior art, the intrafollicular probe 20 is used to deliver laser light 18 of the second wavelength directly into the follicle 13 and of a hair 9 having papilla 12 at skin depth beyond the effective range of the transcutaneous method. This second wavelength of light, in the 440-465 nanometer range, is readily absorbed by either the melanin in the hair 9 or the hemoglobin in the blood vessels 14 surrounding the papilla 12, resulting in damage to the hair shaft 10, photocoagulation of the tissue surrounding the papilla, and subsequent destruction of the hair. In this fashion, a single, inexpensive, laser light source can be used to treat all types of hair in the least painful and most efficient, cost effective, and convenient manner possible.

Although the above description contains specificities pertaining to laser light wavelength, pulse duration, and power level, these specificities should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Variations in primary and secondary laser wavelength, pulse duration, and power level may be possible without significantly reducing the effectiveness of the method. The invention contemplates all variations in these, and all other laser parameters, which accomplish an equivalent result.

Claims

CLAIMS We claim:

1. A method for permanently removing hair from skin by means of laser light having a wavelength which passes thru the skin with minimal absoφtion and which is substantially absorbed by the keratin component of hair, wherein said laser light is directed onto the surface of said skin for a period of time sufficient to cause photocoagulation of said hair.

2. The method of claim 1 , wherein said wavelength of said laser light is 880-930 nanometers.

3. The method of claim 2, wherein: a) a second wavelength of laser light which is produced by known means, such as second harmonic generation or 3 -mixing plus second harmonic generation, from the same laser source which generates the 880-930 nanometer wavelength; b) said second source of light is directed by intrafollicular means to said hair.

4. The method of claim 3, wherein said second wavelength of light is 440-465 nanometers.

5. The method of claim 1 , wherein the duration of the pulse of said laser light is chosen to optimize the heat conducted to the papilla of said hair.