Laser hair removal

This is the 4238th article of Da Yi Xiao Hu

In recent years, laser hair removal, as a relatively common medical cosmetic method, has entered the public's field of vision with overwhelming advertising. So whether it is effective or harmful to the human body must be a question that everyone is very concerned about. Let us understand it scientifically.

1. What is the principle of laser hair removal?

Is there any damage to the surrounding skin?

The more professional laser hair removal is selective photothermal hair removal. Since the hair follicles and hair shafts are rich in melanin, the melanin is distributed between the cells of the hair bulb matrix and can also be transferred to the structure of the hair shaft. Lasers of specific wavelengths can target melanin and perform hair removal treatment accurately and selectively. After melanin absorbs the energy of the laser, the temperature rises sharply, causing the surrounding hair follicle tissue to be destroyed, and the hair will no longer grow.

According to the theory of selective photothermal action, as long as the appropriate wavelength, pulse width and energy density are selected, the laser can accurately destroy the hair follicles without causing damage to adjacent tissues. [1]

2. Who is not suitable for laser hair removal?

Laser technology is suitable for most people. However, the following individuals should avoid laser hair removal:

1. Allergic constitution, scar constitution

2. Syphilis, AIDS, hepatitis patients

3. People with skin inflammation, infection or photosensitive skin

4. Patients with blood diseases or coagulation disorders

5. Women who are menstruating, pregnant or breastfeeding.

6. Patients who have been taking drugs for treating joint pain and vasodilators.

7. People who have used other methods to remove hair within 6 weeks.

8. Do skin color test, people with dark skin.

9. People who have recently taken photosensitizing drugs such as aspirin

10. People who have taken retinoic acid drugs or used cis-retinoic acid within 6 months before treatment

11. People who are allergic to hydroquinone or other bleaching agents.

12. People with mental illness

13. Minors under the age of 14[1]

3. What should you pay attention to before and after laser hair removal?

① Before laser hair removal, the patient should fully understand the treatment process and realize that multiple repeated treatments are needed.

② Those with darker skin should avoid sun exposure as much as possible before surgery, and it is best to use sunscreen 4 to 6 weeks in advance; for those with darker skin due to sun exposure, they should wait for a period of time or take active measures before receiving treatment.

③ Patients at high risk of herpes can receive preventive antiviral treatment before surgery.

④ Shave the hair in the treatment area to prevent epidermal damage caused by hair burns.

⑤ Patients who are very sensitive to pain can use topical anesthetics to relieve pain.

⑥ During the treatment, both the physician and the patient should wear laser protective goggles to prevent eye damage from laser, and use appropriate cooling devices such as cold air, cold gel, etc. to protect the epidermis.

⑦ Under normal circumstances, there may be a mild burning sensation after surgery, and mild erythema and follicular papules may appear on the local skin, which usually disappear within a few hours.

⑧The treatment area does not need to be bandaged. You can apply ice pack for 30 minutes and then apply antibiotic soft gel or skin care ointment locally.

⑨The patient can gently clean the hair removal area twice a day and return for a follow-up visit one week after treatment.

⑩ To minimize pigmentation, use a sunscreen with an SPF of at least 15 before outdoor activities and avoid sun exposure. [1]

4. General steps of laser treatment

① Turn on the power and preheat the machine.

② Preparation of the treatment area: Shave the hair and clean the area to remove grease and dirt before treatment.

③Set treatment parameters and conduct trial treatment.

④ Obtain the optimal parameters and complete the entire treatment.

⑤ Explain the precautions after surgery. [2]

5. What are the side effects of laser hair removal?

How to avoid it?

There is a stinging sensation of varying degrees during the treatment, but it is tolerable. Erythema or follicular papules may appear immediately in the treatment area and will disappear on their own. Purpura may appear in the treatment area of ​​some patients 1 to 3 days after treatment. If the energy density is too high, blisters and erosion exudation may appear in the treatment area. Temporary pigmentation or hypopigmentation may occur, most of which can be restored after a few months, and very few may have permanent hypopigmentation.

With the continuous development of laser equipment, laser hair removal has brought people more comfortable and efficient treatments, and has also made laser hair removal increasingly safe and reliable. However, there are still risks and dangers in choosing non-professional places such as beauty salons without any registration, registration or certification. I hope that everyone will choose a regular hospital and, under the treatment of experienced doctors, reduce the occurrence of side effects and achieve more ideal cosmetic results. [1]

6. Misconceptions about laser hair removal

Q1: Will hair loss affect sweating?

A: Wrong. Hair removal will not affect sweating. We already know that the principle of laser hair removal is that hair follicles absorb melanin, which causes them to shrink and lose their ability to regenerate, thus completing the hair removal process. The human body sweats mainly through sweat glands. Sweat glands and hair follicles are appendages of the skin and do not affect each other. Moreover, laser hair removal mainly targets the melanin in hair follicles, but there is no melanin in sweat glands, so it will not damage sweat glands and will not affect human sweating. [3]

Q2: Will laser hair removal cause more and thicker hair to be removed?

A: Wrong, body hair will not become thicker or more numerous after laser hair removal. Why do some people think that hair will become thicker after hair removal? It may be because of an optical illusion:

Position 2 in the picture is thicker than position 1. After shaving, part 2 is exposed, and visually it feels that the hair has become thicker and thicker, but this is an illusion. So what determines the amount and thickness of body hair? Hair grows from hair follicles. The amount and thickness of hair depend on the relevant characteristics of hair follicles: including the number of hair follicles, the sensitivity of hair follicles to hormones, the health of hair follicles, and the hair growth cycle. Therefore, the amount and thickness of body hair are mainly determined by genes. Any hair removal method will not "kill" hair follicles under safe operation. Because laser hair removal destroys the hair papilla containing melanin, causing the hair follicles to enter a dormant period. Over a longer period of time, it can achieve the effect of reducing the amount of growing hair and making the hair thinner and softer. [4]

Q3: Will the effect of hair removal be immediate after one session? Will I never grow hair again after laser hair removal?

A: Wrong. Usually laser hair removal needs to be done 3 to 6 times. There are two main reasons for this. First, the hair follicles in the skin are mostly bundled together in threes, with the opening coming from the same pore. The hair that grows from one follicle in a group of three can only be destroyed by one treatment in the group. Second, hair growth goes through certain growth stages, namely the catagen, telogen and growth phases. Laser hair removal is 75% effective in the growth phase and 25% effective in the catagen phase. However, there is almost no effect in the telogen phase.

Moreover, currently, laser or intense light therapy devices can achieve permanent hair removal. However, this is not what most people think, that after laser hair removal treatment, hair will not grow for life. The permanence mentioned here is not the real permanence. In fact, the correct understanding of permanent hair removal should be that after laser hair removal treatment, hair will not grow within a hair growth cycle. [5]

After reading this, I believe everyone has a certain understanding of laser hair removal. "Everyone loves beauty", but I hope everyone can do sufficient homework before medical beauty treatment and choose a regular hospital. After all, safety and health always come first.

[1] Source: https://xuewen.cnki.net/CJFD-JTYI201201045.html “Don’t worry about excessive hair, laser can beautify your skin” Family Medicine, Issue 1, 2012

[2] Source: https://baike.baidu.com/item/激光脱髮/362191?fr=aladdin

[3] Source: https://lemon.baidu.com/answer?id=978378&core=978378&fromSSR=1

[4] Source: https://www.zhihu.com/question/23795827

[5] Source: http://tag.120ask.com/jibing/tuomao/939313.html

Author: Shanghai University of Traditional Chinese Medicine

Rehabilitation Occupational Therapy Freshman

2021441013

Xie Jinle