Currently cosmetic skin lasers are generally used to treat the following diseases.
Vascular diseases: e.g., nevus of bright redness, simple hemangioma, capillary dilation.
Pigmented diseases: nevus of Ota, freckles, tattoo removal.
Laser hair removal.
Laser skin peeling, skin rejuvenation, and laser treatment of acne.
I. Vascular diseases
Traditional treatments: surgery, isotopes; non-pulsed lasers (continuous wave or semi-continuous wave lasers) such as argon lasers, copper vapor lasers, which are prone to scarring (5-22%) and persistent pigment abnormalities.
Nowadays, pulsed dye laser is generally used, which is the first laser developed based on the theory of selective laser decomposition and can selectively destroy capillaries, while there is almost no damage to other structures of epidermis and dermis. After laser treatment, the histopathological changes are: the damaged blood vessels are replaced by fibrous tissue. The general wavelengths are: 577nm, 585nm, 595nm, in recent years, the laser for vascular diseases mostly uses 595nm, because the longer wavelength has deeper penetration. The pulse width is 0.45ms-1.5ms, and the pulse width is adjusted according to the diameter of the blood vessel, the thicker the blood vessel, the larger the pulse width should be.
The energy of the appearance of purpura without excessive edema, crusting and blistering is generally taken as the standard in laser treatment of bright red nevus. In general, children < adults; face > neck; dark skin tone < fair skin. Most lasers are now equipped with cooling devices to protect the skin. We have observed that the anatomical location of the lesion, the thickness of the blood vessels, and the epidermal pigmentation of the patient's age are related to the efficacy.
Simple hemangiomas, which generally grow rapidly within 1 year of age and subside at 5-10 years of age, are treated with laser for the following reasons: to prevent further enlargement, to prevent ulceration and bleeding, to facilitate the psychological development of the child, and to provide a better skin condition after treatment than natural recovery.
Facial capillary dilation, 1-2 times cure rate up to 90% or more, need to adjust the pulse width according to the thickness of the blood vessels.
Lower limb vasodilatation, lower limb veins compared with the above vascular diseases: deep location, thick diameter, thick walls, high intravascular pressure so require longer laser wavelength, large pulse width, high energy, with cooling system to protect the epidermis. Long pulse Nd:YAG is reported to be more effective.
Other indications of pulsed dye laser: spider nevus, erythema and capillary dilation of rosacea, venous lake, hypertrophic scars, plaque psoriasis, skin rejuvenation, wrinkle removal.
Side effects: transient purpura, temporary pigmentation changes, scar formation is rare.
II. Treatment of nevus of Ota
Traditional treatment: freezing, chemical peeling, skin grinding, surgical excision, which often have poor efficacy and leave scars. Nowadays, Qs laser is used, and after several treatments, most of the patients with nevus of Ota can be completely cured, and the efficacy of amateur tattooing is better, while the efficacy of professional tattooing is slightly worse.
Nevus of Ota, late-onset bilateral nevus of Ota-like spots, skin pigmentation caused by memantin: using Qs ruby, Qs emerald, Qs Nd:YAG, all can freckle, coffee spot, Becker’s nevus: generally using multifrequency Qs Nd:YAG , flash pump 531nm pulsed dye laser, Qs ruby, Qs emerald, the latter 2 efficacy is unpredictable.
Chloasma: poor effect, easy to recur and even aggravate, generally do not use laser treatment.
Treatment of tattoos
The mechanism of laser treatment for tattoo is generally considered as follows: 1) the high temperature of laser causes chemical changes in the tattoo material, 2) it is broken into very small particles and taken away by phagocytes, 3) it is discharged from the epidermis.
The dye used for the tattoo affects the outcome of the treatment. (Some people use QS Ruby to treat amateur tattoos after 3 treatments 85% of them are completely cured, while professional tattoos after 6 treatments are completely cured 10%, partially removed 70% and almost invalid 20%. (There are also reports of 65% cure rate for professional tattoos after 9 treatments; 90% cure rate for amateur tattoos after 5 treatments.) Laser for tattoo treatment: Q-switched ruby (694nm), suitable for blue and black tattoos; green is slightly worse, red and yellow are not effective. Q-switched emerald (755nm), suitable for blue and black tattoos, green tattoos; red is worse. Q-switched Nd:YAG (1064nm) + frequency doubling (532nm) is suitable for blue and black tattoos (1064)/red (532).
Side effects of laser treatment for tattoos.
Temporary hyperpigmentation 10-50%, easy to occur with short wavelengths.
Very rarely, persistent hyperpigmentation, hypopigmentation and abnormal skin texture may occur.
Yellow tattoos (generally used for cover-up) dyes may turn black under Qs laser action.
For those who systematically use gold preparations, laser treatment may cause the skin to appear gray-blue.
For people who are allergic to tattoo tattoos, laser treatment may cause systemic allergy.
The current problems of laser treatment of tattoos, for some special colors such as yellow treatment effect is not good, for some tattoos, after several treatments, there are still some color residue. In order to reduce the number of treatments, some people use Qs Nd:YAG first and then apply Carbon-based lotion locally and then Qs Nd:YAG again.
Four, laser hair removal
Traditional hair removal methods: hair removal cream, waxing, is temporary, electrolysis, although permanent, but time-consuming, may leave scars.
The current laser hair removal wavelength: 600-1100nm red or infrared light, good penetration, pulse width: greater than 3ms, less than 40-100ms. such as: long pulse ruby laser EpiLaser (Palomar); EpiTouch (Sharplan), long pulse emerald GentleLase (Candela) EpiTouch Alex (Sharplan), semiconductor laser LightSheer (Coherent), pulsed intense light, etc.
Laser hair removal should be noted.
Sun protection: Do laser hair removal should be noted, hair removal area in the week before and two weeks after treatment sun protection.
Two weeks before treatment, hair removal area should not be plucked, waxed or electrolysis hair removal.
Laser hair removal requires multiple treatments.
Laser hair removal generally requires three to six times: because most of the hair follicles are bundled together in groups of three, one treatment can only destroy one of the follicles in a group; hair growth has to go through the anagen phase, regression phase and resting phase, and laser hair removal is effective in the anagen phase, less effective in the regression phase and almost ineffective in the resting phase.
Interval: 4-8 weeks, or when a considerable amount of hair is found to start growing, another treatment is performed.
Side effects of laser hair removal erythema, follicular hyphal-like papules: generally considered to be effective markers.
Hyperpigmentation: race, individual differences, sun exposure, excessive laser energy, excessive coolant, laser handle head overheated from laser exposure or overcooled from refrigerant buildup.
Prevention: light avoidance, depigmentation agent, appropriate energy, avoidance of handle head contact with skin
V. Laser grinding
Although it is said that the traditional laser can also remove the skin superficially, it often leaves a very thick thermal damage area, the depth is not easy to grasp, the postoperative recovery is slow, and the possibility of scar formation is high. Nowadays, the pulsed CO2 laser, pulsed bait laser, overcomes the above shortcomings and is widely used abroad for wrinkle removal, treatment of depressed acne scars, and cosmetology, but it is rarely carried out in China due to the long post-operative recovery period, possible infection, and severe post-operative pigmentation in yellow people. These lasers are: ultra-pulsed CO2 laser, scanning CO2 laser with computer control, and bait laser.
These lasers are infrared lasers with dynamic cooling system, which specifically heats the superficial dermis without damaging the epidermis, causing it to denature and inducing the body’s repair process, producing collagen fibers and so on, thus allowing wrinkles and depressed scars to be repaired. Also, since sebaceous glands are within the range of action of this type of laser, it can be used to treat acne.