Laser Hair Removal Facts

LASER HAIR REMOVAL FACTS

Laser Hair Removal History

Laser light as a tool for unwanted hair removal was first introduced to US market in 1995, when ThermoLase Corporation (San Diego, CA) received FDA clearance for its hair removal device based on Nd:YAG laser[1]. The method suggested use of infrared (IR) laser light in conjunction with a topical light absorbing solution. Though the long lasting effects of that first laser hair removal approach were questionable (in terms of its comparison with electrolysis), its speed and virtual painlessness were so attractive that laser hair removal soon became very popular. It was soon determined that best results in hair removal could be achieved only when the unique laser light property is correctly utilized. The fact that laser emits its light energy in a very narrow spectral range (usually represented in laser specifications by peak emitting wavelength), makes it possible to effectively deliver laser energy right to the hair follicle, without damage to surrounding skin layers. That’s why the search for the laser, which would be best choice for hair removal application, has started right after the first laser appeared in the market. After a number of clinical studies were performed [2-5], the best results were demonstrated with two type of lasers: Ruby laser emitting at 694 nm (red) wavelength and Alexandrite laser that operates at 755 nm (near infrared) line. The clinical advantage of these two lasers was based on the big difference in absorption between upper skin layers (epidermis) and hair follicles containing hair pigmented with melanin. This mechanism of selective targeting of the hair follicles was called selective photothermolysis [4] and is illustrated in the Choice of Wavelength section below, where we give more detailed description of the laser hair removal physics.

Since 1997 many companies in USA and Europe introduced new laser hair removal devices. The lasers for hair removal today come in all shapes and sizes. There are also different lasers that use different wavelengths of light. Some utilize a cooling device and some do not. All laser systems emit a gentle beam of light that passes through the skin to the hair follicle where it is absorbed by the hair. Among all these systems the Alexandrite laser based devices have won the biggest market share. The popularity of these lasers is based on the preferable wavelength of 755 nm, high energy per pulse, which can be delivered at higher speed from a more compact package than in competing Ruby lasers.

Choice of wavelength

Most of the modern laser hair removal systems operate based on Anderson and Parrish’s 1981 principle of selective photothermolysis [4]. Under the principle of selective photothermolysis, when a pigmented target absorbs a particular wavelength of light in an amount of time that is shorter than or equal to the thermal relaxation time of the targeted structure, the targeted tissue will be selectively destroyed without surrounding tissue injury. The absorption properties of the main chromophore of hair follicles - melanin, and surrounding epidermis have suggested that lasers emitting light in red and near infrared spectrum are the best light sources for the hair removal [3,4]. Since melanin in the hair shaft/bulb is the primary chromophore for laser hair removal and because one of these targets (bulb) may be located up to 5 mm below the skin surface, the optimal choice of wavelength depends on both skin penetration depth and melanin absorption. For a typical hair bulb diameter of 0.3 mm located 3 mm below the skin surface, the calculations show (see Figure 1) that among popular wavelengths used for hair removal, the wavelengths in 640-780 nm produce the highest temperature rise per unit fluence (laser thermal efficiency) in the hair bulb.

Figure 1. Temperature rise in an 0.3 mm diameter hair bulb per unit fluence as a function of wavelength.

In simple words, the lasers operating at preferable wavelengths can deliver more heating damage to the hair bulb without burning the surrounding skin. This property of the laser light also gives it substantial advantage when laser is compared to non-laser hair removal devices (such as flash lamp-type light sources with very broad emission spectrum).

Currently, only two types of solid-state lasers emit light at the appropriate wavelengths and with sufficient output energy for the hair removal procedure. These lasers are Ruby laser (694 nm output wavelength) and Alexandrite laser (755 nm central output wavelength). Recent studies have shown that the clinical results achieved by both types of lasers are on par [3], so the technical differences between two lasers are usually seen as an advantage of the Alexandrite. The 810 nm output of the diode lasers, which are also widely used for hair removal, is pretty close to desired wavelength range, but required energy fluence can only be achieved at very long pulses (much longer than typical thermal relaxation time of the hair follicle), compare to the solid-state lasers.

Speed and Cost Effectiveness

The practitioners involved in hair removal procedures always pay attention to the time required to perform treatments. This time eventually determines the cost of the treatment and it strongly depends on the laser performance characteristics. In terms of pulsed lasers there are only two ways to increase the coverage rate of a treatment: increase the pulse repetition frequency (rep. rate), or increase the spot size. How fast a laser covers a treatment area is a product of the spot size and repetition rate (see Table 1).

Table 1. Optimal coverage rates of various lasers

Spot size	Repetition rate	Area coverage rate
Æ15 mm	1 Hz	1.8 cm²/sec
Æ12 mm	2 Hz	2.3 cm²/sec
Æ10 mm	3 Hz	2.4 cm²/sec
9 x 9 mm square	2 Hz	1.6 cm²/sec
Æ9 mm	3 Hz	1.9 cm²/sec
Æ7 mm	5 Hz	1.9 cm²/sec

In most laser designs, an increase of the pulse repetition frequency leads to lower output energy. This contradiction does not allow achieving high fluence (or energy density), required for efficient hair removal, using relatively big laser beam spot sizes. That is why the capability of the hair removal laser to deliver high average power (i.e. high pulse energy at high repetition rates) is the most important factor to consider if one is looking for a cost effective system. Though the typical charges for hair removal procedures are relatively high, it may be still difficult to maintain cost efficient operation of the laser if it isn’t fast enough. The typical costs of hair removal procedures for the customers are shown in Table 2 (this data must be interpreted as a general guideline only and does not represent exact costs, special contracts and treatment conditions that may exist in various locations).

Table 2. Typical costs of various hair removal procedures.

LASER HAIR REMOVAL GENERAL COSTS:
Area Treated	Laser Cost Per Treatment and Average Treatment Time	# of Laser Treatments
Upper Lip	$50.00-$110.00 Per Treatment; Treatment Time 4 Minutes	3 - 8
Chin	$150.00-$350.00 Per Treatment; Treatment Time 5-10 Minutes	3 - 8
Bikini Line	$200.00 -$295.00 Per Treatment; Treatment Time 10-15 Minutes	3 - 8
Underarms	$150.00 -$300.00 Per Treatment Treatment Time 4 Minutes	3 - 8
Man’s Back	$800.00 -$1,200.00 Per Treatment; Treatment Time 1 Hour	3 - 8
Legs (ankle to bikini)	$750.00 - $1500.00 Per Treatment; Treatment Time 1-2 Hours	3 - 8

Finally we can say, that actual treatment time depends on the laser hair removal system technical parameters, certain body area being treated, particular patient skin and hair type and practitioner’s skills and experience. The data in Table 3 can be helpful in order to estimate required treatment times for different body areas, using known hair removal laser specifications.

Table 3. Average sizes of typical hair-bearing anatomical areas.

Site	Approximate Size
Upper lip	15 cm²
Face	80 cm²
Bikini area	125 cm²
Underarms (2)	190 cm²
Man’s back	2750 cm²
Legs (2)	8100 cm²

As an example, it will take DDC Technologies AL-40 Alexandrite laser, (operating at 15 mm spot size, 2 pulses/sec with average 20% overlap) slightly over 15 min to cover the man’s back area. Taking into account some preparation time and possible double treatment in some originally missed areas, the whole procedure can be finished in less than ½ hour.

The only other hair removal method that generally yields permanent results is electrolysis. But even 3-4 laser treatments, typically required to achieve permanent hair reduction in the average patient, are much less time consuming than electrolysis. The table below gives a comparison of time between laser and electrolysis to clear a certain body area one time:

Table 4. Same area treatment time comparison between laser and electrolysis methods.

Men:	Laser	Electrolysis
Back	45 min -3 hours	100-150 hours
Shoulders	10-20-minutes	25-50 hours
Women:	Laser	Electrolysis
Underarms	1-2 minutes	4-10 hours
Bikini	8-10 minutes	5-10 hours
Upper lip	Less than 1 min.	30-60 minutes
Chin	2-3 minutes	1-3 hours
Legs	1 ½ -3 hours	75-150 hours

References:

1. 1. “FDA Approves First Laser Hair-Removal System”, Medical Laser Report V. 9 (5), May 1995;

2. 2. J.C. Walling, D.F. Heller and G.J. Fisanick, “Alexandrite Lasers For Medical Applications” SPIE V.1892 Medical Lasers and Systems II, 1993, pp. 52-62;

3. 3. James Hsia, Karl Pope, “Comparison of the Candela GentleLASE Hair Removal System with Other Technologies”, Candela Corp. press release, 1998; David Goldberg, Rosaline Ahkami, “Evaluation Comparing Multiple Treatments With a 2-msec and 10-msec Alexandrite Laser for Hair Removal”, Lasers in Surgery and Medicine, v.25, 1999, pp. 223-228;

4. 4. B. Finkel, et. al. “Pulsed Alexandrite Laser Technology for Noninvasive Hair Removal”, Journal of Clinical Laser Medicine & Surgery, V.15 (5), 1997, pp. 225-229.

Speed and Cost Effectiveness

Electrolysis