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Laser Hair removal — Transcript

by Understanding Dermatology · 3,736 words · 544 segments · language en · Watch on YouTube

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0:03In the name of God, the Most Gracious,
0:04the Most Merciful. We will, God willing
0:06, start a new lecture in the laser
0:09therapy series. We have already spoken
0:13previously about the basics of laser
0:15therapy and laser safety. Today, we
0:18will talk about something practical in
0:21lasers, which is laser hair removal. Of
0:25course, at the beginning, we want to
0:27know what the indications for laser are
0:32. It is not just something optional or
0:34something aesthetic or something that a
0:39female or a male wants to remove. No,
0:42there are many diseases that involve
0:44excessive hair growth, such as
0:46hirsutism and hypertrichosis. So, for
0:50this, we may also need to perform laser
0:53hair removal. At the same time, there
0:55are some diseases which are follicular
0:57diseases. Follicular disease means we
1:00have a disease related to the follicle.
1:03Like pseudofolliculitis, acne
1:05keloidalis, or hidradenitis. All these
1:09things, if we perform laser hair
1:10removal, they improve. Because this is
1:13a large part of the pathogenesis of the
1:15disease. Therefore, it is not just
1:18something cosmetic and aesthetic. We
1:20will try to understand the subject step
1:22by step. By first wanting to understand
1:26the mechanism of laser hair removal, or
1:29what is called phototricholysis. Before
1:32we begin, we must differentiate between
1:34two things: The hair itself, or the
1:36hair fiber, or the hair shaft. As we
1:38see, this is composed of dead keratin.
1:42And the hair follicle, which is the
1:44part with cells that create the hair
1:46shaft. The process, of course, begins
1:50as soon as we place the laser on the
1:53skin, in the area that has the unwanted
1:55hair we want to remove. This happens
1:59because the hair melanin—these red
2:02dots—the melanin inside the hair, is
2:05what absorbs the laser beam. It is as
2:09if this is the chromophore that
2:11receives the laser and absorbs it. So,
2:13what does this do? This causes heating
2:17of the hair itself. And after that, the
2:20heat is transferred to the green part
2:22around it, which is the hair follicle.
2:25Then, damage begins to occur to the
2:27hair follicle. Once the hair follicle
2:31is damaged, there will no longer be any
2:34hair regrowth, and the laser succeeds.
2:38So the laser must begin by absorption
2:41in the shaft, and then transfer. To
2:45speak about it in a practical way. We
2:49have two things: the laser machine
2:52itself that we want to choose and know
2:55its parameters. We have four things
2:57that must be adjusted. And then, the
3:00patient himself, how to control these
3:03parameters via three things: the
3:06phototype, hair color, and its
3:08thickness. So we will look at them
3:10point by point. First, let's start with
3:12the laser machine. The first thing is
3:15the wavelength. As we said in the
3:17previous lectures on basics, the
3:18wavelength is what determines the type
3:20of device. So we want to know what the
3:23devices are, or what the devices are
3:25that we can use to treat any condition
3:27involving excess hair. Of course, it
3:31must be selectively absorbed by melanin
3:34. Meaning the wavelength emitted from
3:36the device must be absorbed by melanin.
3:39And this brings us back to the curve we
3:41studied. We want to know what the
3:44absorption spectrum of melanin is. If
3:47we look at this curve as we took before
3:51, we will find that melanin is absorbed
3:55at all wavelengths. As we can see right
4:00here. All of this green line wavelength
4:03, it’s all main absorption. It gets
4:05absorbed in everything, in the
4:08ultraviolet and infrared. All three
4:11things, in the ultraviolet, the visible
4:13, and the infrared. And as the
4:15wavelength gets longer, as we can see
4:18here, the absorption decreases. As the
4:21wavelength gets shorter, the absorption
4:23increases. Based on this, theoretically
4:26speaking. Any laser device that emits a
4:30wavelength can be absorbed by melanin
4:33and used for hair removal. But as we
4:37said before, we must look out for other
4:40chromophores. We must look out for the
4:43interaction with other chromophores.
4:45Then, we must also ensure the
4:47absorption level is appropriate. And
4:49that there is good depth. These are
4:50three important factors we will explain
4:52now. What does that mean? I am in this
4:55area, right here. There is good
4:59absorption for melanin. But there is
5:01interaction with hemoglobin. So it is
5:04better not to use devices in this area.
5:07Well, here there is also good
5:09absorption for melanin. It decreases a
5:13bit, true, but there is interaction
5:15with water, and also with hemoglobin.
5:18So we should also avoid this area. To
5:21achieve these three conditions, of
5:24having selectivity for melanin and
5:27avoiding other chromophores like
5:29hemoglobin and water, I must avoid this
5:33area entirely. And I will avoid this
5:36area. And I will focus on the part in
5:37the middle. So, the absorption
5:39coefficient must be appropriate. It is
5:42very high here, low here, and medium
5:45here. For depth of penetration, we have
5:48a rule: the longer the wavelength, the
5:50better the depth of penetration. So,
5:53here the penetration is short, here it
5:56is deeper. But because of other factors
5:59, we always choose the middle area.
6:03This middle area is the best for hair
6:06removal. Why? First. We stay away from
6:10other chromophores. As we can see, we
6:12stay away from hemoglobin, which is
6:14this red area here. And we stay away
6:16from the water here. And this area is a
6:19medium area. It is medium in everything
6:22; the absorption coefficient is not too
6:24high or too low, it's moderate.
6:28Therefore, the depth of penetration is
6:30reasonable, neither short nor long.
6:34Looking down here, we see it starts
6:36from about 600 and goes up to 1000,
6:391100, 1200; in this whole range. This
6:42is the area we use for laser hair
6:45removal devices. 600 to 700 nanometers
6:48is our starting point, up to 1000 or
6:511100 as our end point. What are the
6:54devices found here? There are four
6:57devices we must understand and know
6:59well. The first is Ruby at 694, then
7:03Alexandrite at 755, Diode at 800, and
7:07Nd: YAG at 1064. So, there are four
7:11main devices shown below with their
7:15wavelengths. These are the ones we use
7:18for laser hair removal. And we know why
7:21these four. Right. These are their
7:26specifications. Their names, Ruby, Alex
7:29, Diode, and Nd: YAG, and their
7:31wavelengths. There is one more
7:34important point. If we focus on these
7:37four, the first one, the Ruby, has the
7:40shortest wavelength. Then, the
7:42wavelength continues to get longer up
7:44to the Nd: YAG. We will exclude the
7:46Ruby. Its use in laser hair removal is
7:49almost non-existent. We always start
7:52with the Alex. Possibly the Diode. Or
7:54maybe the Nd: YAG. So, why specifically
7:56the Ruby? The Ruby has a few drawbacks.
7:58It is, first of all, very short. And
8:00since it is...very short, its
8:02penetration is...low. The second thing
8:07is that its absorption is very high.
8:10This should be an advantage, the
8:11highest absorption. Because our curve,
8:14as we said, goes downwards. Meaning it
8:16goes down like this with the wavelength
8:18. So, it should have the highest
8:19absorption among them. And that should
8:21be a good advantage. But at the same
8:22time, it is a disadvantage. If someone
8:24has dark skin and their skin has a lot
8:26of melanin. This high absorption
8:28coefficient, or high absorption, might
8:31cause a skin burn. It can cause damage
8:33and lead to complications. So, after
8:35choosing four, we will exclude the Ruby
8:38. And we will work with the three: the
8:41Alex, the Diode, and the Nd: YAG. Now,
8:44regarding the other things we adjust in
8:46the device, or want to understand. We
8:48already know the wavelength, which is
8:50the type of device, and we have learned
8:51that. We have three more things left.
8:55The first is the pulse duration. And if
8:58you remember from the basic lectures.
9:00The pulse duration here works in normal
9:02mode, which is in milliseconds. It is
9:06simply that if I have a small hair. A
9:08thin hair, as you can see, its follicle
9:12is also small. So we choose a short
9:14pulse duration for it. A short pulse
9:16duration. The larger the hair gets and
9:19becomes thick, it means its follicle is
9:21...larger, so we lengthen the pulse
9:23duration. That is the whole idea. And
9:26this is the most important point in a
9:27nutshell. If I am working, for example,
9:31with 20 milliseconds on a thin hair, or
9:3325, I might find a thick hair and reach
9:3630, and so on. So the thicker the hair,
9:40the thicker the follicle, so I need
9:41more time. Therefore, I increase the
9:44pulse duration. The next element is the
9:47spot. Size; of course, the spot size in
9:50the device involves multiple handpieces
9:53that we use. They have specific
9:56diameters in millimeters: 5 mm, 10 mm.
10:00Of course, a big spot size is always
10:03better for two reasons. As you can see,
10:07the larger the spot size, the deeper
10:09its penetration. So it is more
10:11effective. If I work with a small spot
10:14size like this, it is relatively
10:16superficial. So the larger the spot
10:19size, the better. Because it reaches
10:21deeper. And the second thing is that
10:23this allows me, if I. Am working on a
10:25large area. To make the session a bit
10:29faster. And we finish quickly. So it is
10:32preferred to use a larger spot size. As
10:35much as possible. We come to the next
10:38point, which is the fluence. This is
10:41the final point regarding the device.
10:42We learned the device type. We learned
10:44the pulse duration. The spot size. The
10:47fluence. The fluence is the energy that
10:49we use. And it is measured in Joules
10:51per square centimeter. You find on the
10:54device 15, 20, or 10 depending on the
10:56device. The fluence should follow a
10:59very simple rule. We use sufficient
11:02fluence to cause destruction to the
11:04hair. And to the hair follicle as well.
11:08And we use the largest amount possible.
11:10The highest fluence possible that we
11:12can use. We use it, but of course, we
11:14shouldn't exceed that too much. Because
11:16if we increase it, as we covered in the
11:18laser-tissue interaction. In the early
11:21lectures, it will cause transmission
11:23and this. This is not good, nor is
11:26using low fluence either. Low power or
11:30low energy, because this sometimes
11:32creates a paradox; it does the opposite
11:35, meaning it stimulates hair growth. So
11:39this is a very, very important point.
11:42We must use the appropriate fluence;
11:44less of it. Is harmful, and more of it
11:48is also harmful, so how do we know? We
11:51do something very famous called test
11:53doses. We experiment. And if you are
11:57giving a good amount of energy, an
12:00immediate response occurs. We see two
12:04things. The hair shaft that remains, we
12:07leave. A small piece of the hair shaft
12:09vaporizes right in front of us. I mean,
12:12we shave the skin. The hair becomes 1
12:14mm, 2 mm. Just a little bit, this is if
12:16the power is not sufficient. You will
12:18find the hair as it is. Nothing
12:19happened to it. But with sufficient
12:21power, you see it burning in front of
12:23you. It happens. It undergoes
12:24vaporization, it evaporates before your
12:26eyes, okay. The second thing, I'm not
12:28looking at the hair shaft, of course.
12:30But I want the follicle. So after a few
12:32minutes, I see perifollicular erythema
12:35and edema. You find edema around each
12:39follicle. And it means a reaction has
12:43started in the follicle. So this is
12:46called the end. Point, the good
12:48end-point for me, which tells me that
12:50my power was good. Let's get to the
12:53patient quickly. How did we learn about
12:55the device? Let's look at the patient.
12:56Regarding the patient, three things
12:58interest me. Which are their phototype,
13:01their skin, and the hair itself. We
13:03look at its color and we look at the
13:04thickness. These are the three things
13:07that control laser hair removal.
13:10Regarding the skin phototype, look at
13:12this diagram. Dark skin versus fair
13:16skin. Dark skin epidermis has a lot of
13:19melanin. So when we use the laser to
13:24reach the follicle, as we see here in
13:27green, part of the laser beam and
13:29energy is absorbed in the epidermis. So
13:33the epidermis gets heated, it burns,
13:36and gets damaged. And at the same time,
13:39it takes part of the energy that was
13:41supposed to reach the hair follicle.
13:44This is unlike fair-skinned people. In
13:46fair-skinned people, theoretically, the
13:48epidermis is clear, or the amount of
13:50melanin is low. So these problems don't
13:51happen. Meaning there is no heating of
13:55the epidermis, no damage, and no loss
13:57of energy or anything. That's why for
14:01dark-skinned people, their problem is a
14:03dual problem. Dark, dual problem, I am
14:06afraid of two things. Part of the laser
14:08is absorbed in the epidermis, and this
14:10causes damage to us. That's the first
14:13problem, that I get damage to the
14:15epidermis. And the part that reaches
14:18the hair follicle afterwards is minimal
14:20. The efficacy decreases. So I increase
14:24the power a bit to compensate, which
14:26increases damage to the epidermis. And
14:29so on, it becomes a very big problem.
14:32How do we solve that? There are many
14:36ways, four things we do, and maybe
14:39others, five for example, that we do
14:41for dark skin types. First, we use
14:45longer wavelengths. What does that mean
14:47? We said we have four devices. We've
14:50already ruled out the Ruby. Now we have
14:53the Alex, Diode, and Nd: YAG. As the
14:56skin type—look at this chart—as the
14:58skin type gets higher. We move toward
15:01four, five, and six. You should also
15:03use a longer wavelength. As you can see
15:05, take the longest one, the Nd: YAG.
15:08Why do long waves have advantages for
15:12dark skin? First, because it's a long
15:16wavelength, it reaches deeper. And it
15:20...Won't be as concentrated in the
15:22epidermis, like a short one would.
15:25Meaning, if I used a short one like
15:26Ruby, most of it stays in the epidermis
15:28and a small part in the dermis, so the
15:29damage is quite dangerous. But the
15:32longer the wavelength, the greater the
15:35part that reaches the dermis. Therefore
15:39, I provide some protection to the
15:41epidermis. In addition to something
15:44very important from the curve, as we
15:46said, the further down we go, the
15:48longer the wavelength, the lower the
15:50absorption coefficient, meaning the Nd:
15:52YAG absorption is low. This ensures
15:55there is no major risk to the epidermis
15:57. So that is a very, very simple rule.
15:59The darker the skin, the longer the
16:02wavelength we use. We choose a device
16:05with a longer wavelength. Meaning, the
16:08Nd: YAG is better than the Diode, and
16:09the Diode is better than the Alex, and
16:11avoid the Ruby entirely. Well, this is
16:14another summary of what we just said.
16:17That shorter wavelengths have high
16:20absorption. Therefore, it is preferable
16:24to keep those for fair skin. But for
16:27dark skin, let's use longer wavelengths
16:31. What else can I do besides using?
16:34Longer wavelengths. There is a very,
16:36very important rule. Use the lowest
16:39fluence possible. Do not use high
16:43energy. So that burns don't occur in
16:45the epidermis. And keep the wavelength,
16:48our pulse duration, as long as possible
16:51. So there are two things we do that
16:53are opposites. It is wrong to use high
16:56power and short duration. No. That is
16:59for dark skin. Try to use the longest
17:02possible pulse duration. And keep the
17:06power as low as possible. But of course
17:09, not so low that it doesn't have an
17:11effect, or causes a paradox. No, keep
17:13it at a reasonable effect level. And of
17:16course, we pay close attention to
17:18epidermal cooling. This is important.
17:20Because when I apply ice, for example,
17:22or use a cooling agent on the skin like
17:25cryogen. This keeps the epidermis cool.
17:28So it isn't affected much by the heat
17:29that occurs. These are the important
17:31things we use for dark. Skin. When we
17:34look at the hair itself, we look at two
17:37things: its color and its thickness.
17:40Meaning, thin or thick, like that. For
17:42our color, we have two possibilities.
17:44If it's light-colored, yellow or brown.
17:47Or if it's a dark color, black. Let's
17:50focus now. The light color has very
17:52little melanin. So, it's a chromophore
17:56that absorbs little energy. I must use
17:58high energy. How do I do that? Increase
18:01the fluence. Use high fluence, and use
18:05a device with high absorption. Meaning,
18:09what should I lean towards? Towards
18:11short, not long wavelengths. Use, for
18:13example, the Ruby laser. If possible,
18:17use the Alexandrite. But don't go for
18:20the Nd: YAG because the Nd: YAG...Or
18:22that Nd: YAG will have low absorption.
18:26And here I have light hair, which needs
18:28a lot of energy to be affected. The
18:31opposite is true if it's black. If it's
18:33black, it will absorb......everything,
18:35so I can give it very low fluence. And
18:37use any device. Even if the device has
18:40low power, it will be fine. If the
18:42power is high, it's also fine, no
18:44problem at all. So that matters
18:46regarding the hair color itself. Now,
18:50the hair thickness, it could be fine or
18:53it could be coarse. Of course, we
18:56discussed pulse duration before. I am
18:58reminding you again, if it's thin, we
19:00keep the pulse duration short. And if
19:03it's thick, we keep the pulse duration
19:06long. But here I am talking about
19:08another element, energy. It is very
19:11clear that if the hair is thin, just
19:14like light hair, it needs more energy.
19:18Unlike if the hair is thick or has a
19:20lot of chromophores. So, any small
19:23amount of energy will result in a very
19:25strong net result. So, for thin hair, I
19:28must increase the energy. Just like
19:30light-colored hair. But give it a short
19:32pulse duration. Thick, dark hair does
19:36not need a lot of energy. So, decrease
19:40the energy or fluence. But because it
19:43is large and the follicle is large, I
19:45must increase the pulse duration. Now,
19:47this is a summary, meaning we are
19:49putting together the three things we
19:51mentioned. We said for our patient,
19:53there are three things I look at before
19:55deciding what to do. I look at my skin
19:59phototype, fair to dark. We agreed that
20:04as the skin type goes up—3, 4, 5, 6
20:06—the higher it goes, the more I move
20:09toward long wavelengths, as you can see
20:11. I move from Ruby to Alexandrite to
20:13Diode. The second thing is the hair
20:16color itself. The darker the color, the
20:20more I can use devices with......low
20:23power for light colors. Meaning, for
20:26light brown things, as you see here. I
20:28must use strong things for them. Use
20:30Alexandrite for them like this. Stay
20:31away from the Nd: YAG. Because the Nd:
20:33YAG will be weak. Keep it for people.
20:34The dark skin or even dark hair; the
20:37hair diameter is the third element, too
20:40. Thin hair has few chromophores, it is
20:43weak and needs high power, but it needs
20:46a short duration, which is why things
20:49with high power, like Ruby and
20:51Alexandrite...Are used for fine hair.
20:56We will summarize all of this later.
20:58But let me say something important, if
21:00I am talking about the Nd: YAG as a
21:02device. It has the longest wavelength,
21:04the longest of them all. It is one of
21:06the most frequently used devices. I
21:08want to know its advantages and
21:09disadvantages. Its advantage is that it
21:11is suitable for dark skin and fair skin
21:14. And for everyone, really. Everyone
21:16can use it. The second thing is its
21:20deep penetration. It reaches a
21:24sufficient depth because it has the
21:25longest wavelength. Its disadvantages
21:28are well-known; it is relatively weak.
21:29Because its absorption coefficient is
21:32low. And this weakness makes it
21:36unsuitable for thin hair or hair with
21:38little melanin. As we said, it needs
21:40the hair to be dark. And it needs the
21:43hair to be coarse, thick. Of course,
21:47that is why they always said something
21:49very important in laser hair removal.
21:52That the ideal candidate, the best
21:54person for laser hair removal, is one
21:56who has all three traits we look for.
21:59Skin phototype should be white,
22:01light-skinned. Because those with light
22:04skin, what about them? I am not worried
22:07about their epidermis, and I can work
22:09well. The second thing, their hair
22:11should be what? It should be dark, a
22:13dark color. It has a lot of black
22:16chromophores. It won't need any
22:17specific device to work on it. And the
22:20next thing is that it should be thick
22:22or terminal hair. So these are the
22:24three ideal specifications. As these
22:26factors change, we need to be a bit
22:28more careful. If the skin is dark, we
22:31must be careful. If the hair is thin,
22:33weak, or has little melanin, we must
22:35increase the fluence and so on. Okay.
22:39Finally, this slide is very, very
22:41important, and we will conclude with it
22:43, God willing; it summarizes the three
22:45parameters we mentioned regarding the
22:47patient and how you should act, so
22:49let's focus on it very well. I will
22:53start with the skin type. The higher
22:55the skin type, meaning the person
22:57getting hair removal is darker or tan.
23:01We do three things instinctively. The
23:04first thing. Use a high, long
23:06wavelength. Meaning, use an Nd: YAG
23:09device, for example, or a diode, or
23:11something similar. The second thing is
23:14to reduce our power and increase the
23:17pulse duration. That is for skin type.
23:20Now for the hair itself. For light
23:22versus dark hair color, for light hair,
23:25I must increase the power. For dark
23:28hair with a lot of melanin, we reduce
23:30the power. As for the thickness of the
23:34hair, for thin hair, we handle it in
23:36two ways. I must give it high power.
23:41Consequently, I choose a device with a
23:43high absorption coefficient. And I keep
23:48the pulse duration short because it is
23:50thin. The thickness of the hair or its
23:54size is related to the pulse duration.
23:56The larger the target, the more pulse
23:58duration it needs, and vice versa. So,
24:02we have reached a conclusion for laser
24:04hair removal in a practical way. And
24:08God willing, we will continue the rest
24:10of the laser dermatology lectures in a
24:12practical manner, God willing.

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