This article has been translated. For the original please click here.

Effects / principles of laser treatment in cosmetology to improve spots and acne scars and types ...



The principle of laser treatment in cosmetology and the type of laser that improves spots and acne scars

Laser treatment is said to be one of the treatments that is easy to receive even for the first time in cosmetic medicine because it does not burden the body such as swelling and bleeding .

Since there are various types of lasers, it is possible to select a laser according to the symptoms and desired effects such as improvement of skin problems such as spots / freckles, chloasma, acne scars, pore troubles, fine wrinkles / sagging, and hair loss. It will be done.

In order to receive better laser treatment, it is safe to know the mechanism and type of laser used in cosmetology and the symptoms that can be improved .

The principle that laser treatment works only on specific substances

Laser is an abbreviation that stands for "Light Amplification by Stimulated Emission of Radiation" and means "amplification of light by stimulated emission".

White light such as the sun's light and incandescent light bulbs is a collection of multiple wavelengths (wavelengths), so when passed through a "prism" that disperses the light, it separates into seven colors.

Lasers, on the other hand , artificially extract and amplify one specific wavelength (one color of light) from the wavelength of light, and have the characteristic of traveling sharper and in a straight line than light .

"Laser media" such as gas, solid, liquid, and semiconductor are used to extract wavelength from light. Laser media include carbon dioxide, ruby, Alexandrite, ittrium (Y), aluminum (A), garnet (G), etc., and the lasers produced from each are "carbon dioxide laser" and "ruby" based on the laser medium. It is called "laser".

In aesthetic medicine, the wavelength characteristics of lasers are utilized. In addition, the parameters of irradiation time and irradiation energy are important.

Laser wavelength

If you want to improve the spots, irradiate the spots with a laser and it will react only to the spots. This is because the wavelength is absorbed only by the melanin pigment that causes the stain . When the wavelength is absorbed, heat and shock waves are generated, destroying or crushing the melanin pigment. The finer melanin pigment is excreted from the body by the metabolism (turnover) of the skin, and it can be expected to have the effect of thinning the spots.

In this way, the wavelength of the laser has the property of being absorbed only by a specific substance. In aesthetic medicine, lasers with wavelengths that are absorbed by the black pigment of melanin and the red pigment of hemoglobin are used to improve spots, freckles, bruises, and reddish faces.

Laser wavelength type

There are various types of lasers used in cosmetology, and the substance of the skin that is absorbed differs depending on the wavelength of each laser. Therefore, the laser that is suitable for treatment is selected according to the target causative substance.

Laser wavelength description

Main types of laser wavelength Absorbed skin substances
hemoglobin melanin moisture
KTP laser 532nm
Die laser Around 585nm-595nm
Ruby laser 694nm
Alexandrite laser 755nm
Diode laser Around 810nm to 1450nm 〇 at 1450nm
Nd: YAG (neodymium yag) laser 1064nm
Er: YAG laser 2940nm
Carbon dioxide laser 10600nm

It is said that the shorter the wavelength of the laser, the deeper the skin surface, and the longer the wavelength, the deeper the skin. This is called "depth of invasion" and is used as an index of each laser irradiation action.

Wavelengths that are easily absorbed by moisture, such as "Er: YAG laser" and "carbon dioxide laser," are immediately converted into heat energy on the surface of the skin. Therefore, although the wavelength is long, the depth of penetration is shallow.

Laser irradiation time

The laser irradiation method includes pulse irradiation, which irradiates intermittently at regular intervals, and the laser irradiation time per shot by pulse irradiation is called "pulse width".

In order for laser treatment to improve skin problems, the pulse width must also be appropriate.

Appropriate pulse width means that the thermal effect is limited to the target such as stains that you want to improve . For example, in improving blemishes, normal skin cells are more likely to be damaged if they affect the tissues around the blemishes.

If the action of the laser does not spread to the surroundings and it is within the time (heat relaxation time *) that only the stains are settled, damage to the surrounding skin tissue can be prevented . The heat relaxation time depends on the substances present on the skin as follows.

* The time from when the temperature of the target that emits thermal energy reaches the maximum temperature to when it drops to 50% of the temperature.

size Heat relaxation time
Hair follicles 200 μm-300 μm
Capillaries 20 μm
50 microseconds
Melanosome * 1 μm
50 nanoseconds
* Melanosome: Organelle that stores melanin pigment

In aesthetic medicine, it is necessary to irradiate with a laser with a pulse width shorter than the above heat relaxation time, that is, a time shorter than the millisecond (1/1000 second) unit, and the following are used in laser treatment. It is a laser with a wide pulse width.

Picoseconds (ps) 1 / 1,000,000,000,000s (1/1 trillion seconds)
Nanoseconds (ns) 1 / 1,000,000,000s (1 billionth of a second)
Microseconds (μs) 1 / 1,000,000s (1 / 1,000,000 second)
Milliseconds (ms) 1 / 1,000s: Long pulse

Laser pulse width description

A laser with a pulse width in milliseconds is called a "long pulse laser", and a laser with a pulse width shorter than nanoseconds is called a "short pulse laser".

A picosecond laser in picosecond units is a short pulse laser.

Q-switch is a technology that outputs a laser

Nanosecond lasers with a pulse width of nanoseconds are often referred to as "Q-switched lasers." Q-switched laser Q is an acronym for quality value, which stands for the quality of the equipment that makes the laser, and "Q-switched" is a technology that outputs a high-energy laser.

Q-switch technology has made it possible to store laser energy and emit it at once with a very short pulse width (in nanoseconds). Picosecond lasers are also Q-switched lasers, but in aesthetic medicine, Q-switched lasers generally refer to nanosecond lasers .

Laser irradiation energy

In addition to wavelength and pulse width, irradiation energy (fluence) is also important in laser treatment. If the irradiation energy is low, the target such as stains cannot be destroyed sufficiently, and if the irradiation energy is too high, there is a high possibility that burns and scars will remain .

When the pulse width is in picoseconds, the object is crushed by a shock wave instead of heat. Since the shock wave has a large instantaneous peak power, the target can be crushed even with low irradiation energy. In other words, the shorter the pulse width , the stronger the instantaneous peak power, so even if the irradiation energy is low, it is possible to crush small substances, and the risk of heat damage to healthy skin tissue is reduced. Will be.

In a nutshell, the new laser treatment principle is that the longer the irradiation time, the more likely it is to cause scarring.

Source: Practical Laser Treatment: Journal of the Japanese Dermatological Association / Vol. 115 (2005) No. 11

Name of laser treatment

You can tell the wavelength and pulse width from the name of the laser

Lasers are laser media that extract wavelengths from light and are named after carbon dioxide lasers, ruby lasers, etc., so you can tell the wavelength from the name of the laser. It is also called by multiplying the pulse width, in which case it is called "long pulse alexandrite laser" or "Q-switched YAG laser".

Some lasers are called laser irradiation methods and treatment methods.

Lasers also include lasers that are referred to by names other than the laser medium and pulse width.

Fractional laser that irradiates in dots

Fractional laser is a method of irradiating a laser with a large number of fine dots . Instead of irradiating the entire area evenly, irradiate it in dots, and dare to intersperse the parts that the laser hits and the parts that do not hit. It is said that the area that was not exposed to the laser supports the recovery of the area that was exposed to the laser, and the skin recovers faster than the entire area.

Fractional laser does not irradiate the entire surface of the treated surface with a laser, but irradiates the skin with a microbeam at a constant density while leaving normal skin, which is used for the subsequent wound healing mechanism of the skin. It is a device that aims to produce a skin resurfacing effect.

Source : Optical characteristics of fractional laser treatment equipment: Journal of Japanese Society of Laser Medicine / Vol. 33 (2012) No. 2

Fractional lasers are further divided into two types.

Evaporative fractional laser

Abrasive fractional lasers are transpirational fractional lasers . Evaporation of water as a gas is called evaporation, and vaporization of tissue by evaporating water is called transpiration.

There are two main types of lasers that are easily absorbed by water, the "Er: YAG laser" and the "carbon dioxide laser", and they are often used to improve raised skin problems such as moles. Since the treatment is performed like scraping the skin, a scab is made, but a significant improvement in symptoms can be expected.

Non-transpirational non-abrasive fractional laser

A non-abrasive laser is a laser that does not "transpiration". Compared to ablative laser, it is a popular irradiation method because it can be expected to be effective while suppressing damage to the skin . Lasers use wavelengths around 1200 nm to 1500 nm. Lasers in this wavelength band have a moderate water absorption rate, and are said to stimulate the dermis layer, which contains collagen and elastin, which affect the firmness and elasticity of the skin, by heat and activate the function of fibroblasts that proliferate them. I will.

In addition, since a laser with a wavelength that absorbs water slowly is used, it rarely creates a visible scab like an abrative laser.

Laser toning to improve skin tone

Laser toning is used to improve the tone of the skin. It is expected to improve skin quality and pigment, and is often used as a treatment for chloasma.

There are many skeptics about the effect of laser alone on chloasma, and many treatments are performed in combination with tranexamic acid. It is said that liver spots are related to factors such as the effects of ultraviolet rays, hormonal changes, stress, genetic predisposition, and vascular action of the dermis.

Various studies have been conducted on treatment methods such as high frequency (RF) treatment, treatment with dye laser that acts on vascular lesions, phototherapy, and laser treatment, but it is said that there is still no "reliable treatment method".

Laser shower and laser facial

Long pulse Nd: YAG laser or long pulse alexandrite laser is a method of hollow irradiation with the laser irradiation surface away from the skin . Since the irritation is mild, it is said that it has the effect of increasing collagen in the dermis layer and promoting the improvement of firmness by repeating the treatments and treating the entire face instead of destroying the cause of specific skin problems. ..

The name of the laser treatment of the medical institution

Lasers can be categorized by various axes such as laser medium, pulse width, irradiation method, and treatment method, but various machines are being developed by cosmetic medical device manufacturers.

There will be multiple machines for each of the "picosecond laser", "Q-switched laser", "laser toning", etc.

Some medical institutions call it the "picosecond laser" treatment menu, while others call it the machine name "picosecond", and the names vary from medical institution to medical institution.

Compare laser treatment with other cosmetology treatments

Difference between laser treatment and light treatment

Light therapy, which is similar to and different from laser therapy , irradiates a milder light energy compared to laser, so downtime tends to be shorter .

In addition, while lasers have a specific wavelength, light contains various wavelengths, so it is possible to work on different skin problems such as age spots, freckles, and redness of the skin at the same time. Therefore, it can be said that phototherapy is suitable for approaching multiple skin problems, and laser treatment is suitable for partial skin problems .

However, because it has various wavelengths, energy is dispersed, and it is difficult to give energy specifically to each problem, and the effect is relatively mild.

Difference between laser treatment and radio frequency (RF) treatment

High frequency (radio wave / RF) is a kind of electromagnetic wave like light. Since the high frequency band is the frequency band of radio, it is also called RF, which is an acronym for Radio Frequency in English.

Lasers irradiate strong energy in a short time, while high frequencies apply relatively weak energy for a long time to heat the deep part of the body . By doing so, it promotes blood flow and metabolic power, aiming to improve skin firmness and slimming effect. There are also machines that can perform light therapy and high frequency therapy at the same time.

Difference between laser treatment and HIFU

HIFU (High Intensity Focused Ultrasound) is a punctate heat of about 70 ° C that acts on the dermis layer and the underlying SMAS layer (superficial fascia) without damaging the skin surface . It can be expected to improve deep wrinkles and sagging, and to have a slimming effect. Also, compared to radio frequency (RF) treatment, pain tends to be stronger depending on the irradiation site, but it is said to be a highly effective sagging treatment.

Difference between laser treatment performed at medical institutions and home cosmetology equipment

There are various models of household cosmetology devices such as hair removal, LED, and RF, and anyone can easily purchase them. However, there is a clear difference between home cosmetology equipment and aesthetic medicine laser machines due to the rules stipulated by the Pharmaceutical Machinery Law.

Anyone can use a home-use cosmetology device safely, and it will be "a device that does not affect the structure and function of the skin and body . " For this reason, household cosmetologists do not have the effects of "small face", "wrinkles and blemishes disappear", and "sag improvement", and the expression in advertisements is illegal. Cosmetology machines can only be used by nationally qualified healthcare professionals.

Laser treatment and laser type according to skin problems

Treatment of age spots and freckles

The treatment is performed at a wavelength that is absorbed by melanin, and the destroyed melanin is gradually pushed out to the surface of the skin by turnover and is naturally discharged .

Depending on the irradiation method, the treatment site may look like a thin scab, but it will come off naturally in about 1 week to 10 days. After the procedure, tape protection or ointment may be required.

Main lasers to use

  • Long pulse laser
  • Nanosecond laser
  • Picosecond laser
  • Er: YAG laser, carbon dioxide laser, etc.

Melasma treatment

The skin is layered from the outside with the epidermis layer and the dermis layer. Chloasma mainly appears in the epidermis layer, but some are mixed in the dermis layer.

Therefore, treatment may be performed with a phototherapy machine that acts on the epidermis layer, but it is said that chloasma is exacerbated by stimuli such as rubbing , and stimuli are given using nanosecond lasers and picosecond lasers. It is common to use a combination of laser toning, which irradiates with low output, and oral administration of tranexamic acid.

Main lasers to use

  • Laser toning

Improvement of fine wrinkles, sagging, pore troubles, acne scars

Laser treatment can be expected to improve fine wrinkles and early sagging. When laser heat energy is applied to the dermis layer of the skin, it is said that the function of the dermis layer is activated by stimulating fibroblasts that increase collagen and elastin that maintain elasticity and elasticity. It is said that the activation of the dermis layer improves the condition of the epidermis layer above the dermis layer, and improves the overall skin quality such as acne scars and pore opening .

Immediately afterwards, redness, burning, and tingling may occur, but it is said that it will subside in about 2 to 3 days. Makeup after treatment is possible, but depending on the type of laser, makeup may not be possible for 24 hours, so please check with your doctor in advance.

Main lasers to use

  • Long pulse laser
  • Nanosecond laser
  • Picosecond laser
  • Fractional carbon dioxide laser, etc.

Mole removal

In rare cases, it may be malignant melanoma instead of a mole, so early consultation is important if you are concerned . Mole with a ridge is usually a scab because it is a procedure that scrapes the skin, but it is not uncommon for the treatment to be completed with a single procedure.

Main lasers to use

  • Nanosecond laser
  • Picosecond laser
  • Er: YAG laser and carbon dioxide laser
  • Fractional carbon dioxide laser, etc.

Removal of tattoos and bruises

Similar to spots and moles, it is treated with a laser with a wavelength that is absorbed only by the pigment in the skin. Previously, the pigments that could be treated were limited, but with the advent of picosecond lasers, it is said that it has become easier to remove various pigments such as red and blue .

The number of treatments for tattoo removal and bruise treatment varies depending on the size of the treatment site, and in many cases repeated treatment is required.

Main lasers to use

  • Nanosecond laser
  • Picosecond laser
  • Carbon dioxide laser, etc.

Medical laser hair removal

It is possible to remove hair by irradiating the melanin of the hair with a laser and causing heat damage to the hair matrix cells that grow the hair and the bulge that produces the cells. It damages the cells involved in hair growth by heat and destroys them to stop the growth of new hair .

Hair has a cycle called the hair cycle, and in hair removal treatment, the hair in the growth phase cycle is irradiated. Since the hair cycle is different for each hair, it is necessary to repeat the treatment multiple times.

Main lasers to use

  • Long pulse laser (Alexandrite laser, Nd: YAG laser, diode laser)
  • (Medical laser hair removal also uses an optical IPL treatment machine)

Laser treatment precautions

The pain of laser treatment is like a rubber band

Depending on the symptoms and the area to be treated, laser treatment may cause pain like a rubber band depending on the irradiation method . Some medical institutions use local anesthesia (including cream tape) at the treatment site.

Laser treatment precautions and aftercare

You may also feel redness and burning after the procedure . In that case, wrap the ice pack in a clean cloth to cool the affected area. These symptoms are most likely to subside within hours to days.

The skin after the treatment is easy to dry, so please take good care of moisturizing. When you go out, you need to take proper measures against UV rays and be careful not to irritate your skin due to massage of the affected area or rubbing due to excessive face washing.

Excessive blood circulation may increase redness and itchiness at the irradiated area, so you should refrain from drinking alcohol, taking a long bath, or strenuous exercise on the day of the event. In addition, stimulating the itchy area may cause complications, so it is recommended to take measures such as cooling.

A skin-beautifying drug that should be used in combination with laser treatment

  • High-dose vitamin C infusion (whitening effect, antioxidant effect, immune function strengthening effect)
  • Cinal (suppression of melanin pigment production, promotion of reduction of ready-made melanin pigment)
  • Tranexamic acid (suppression of melanocyte activation, anti-inflammatory effect)
  • Drinking sunscreen (sunburn damage care with antioxidants)

In order not to fail in laser treatment

The right time for laser treatment

Laser treatment is basically possible at any time of the year, but it is important to prevent UV rays after treatment. Therefore, those who are "not confident in thorough UV protection care" or "have a lot of outdoor activities" should consider performing the treatment in the fall and winter, avoiding the spring and summer when the UV rays are strong .

What you should pay attention to is the treatment for weddings and events. Depending on the irradiation method, it may temporarily become a scab, so plan the treatment at a time when you can afford to deal with skin problems.

Laser treatment and vinyl skin

"Vinyl skin" is said to be caused by excessive skin care and beauty treatments. At first glance, it is often thought that the skin is shiny and beautiful, but the texture has been worn out by wrong skin care with strong friction, peeling in a short period of time ignoring the cycle of skin metabolism, and laser irradiation. It is that.

The texture that expresses the beauty of the skin, such as "fine texture" and "fine texture", refers to the state in which the skin grooves and hills on the surface of the skin are regularly arranged. .. If this arrangement is disturbed by ultraviolet rays, friction, or excessive skin care, the barrier function of the skin will be weakened and the water retention capacity will be lost, causing rough skin and aging, so caution is required.

With proper laser treatment, you don't have to worry about vinyl skin. Under the diagnosis of a doctor, aim for youthful and beautiful skin by treating the symptoms according to the correct cycle.

(Updated January 2021)