The effect of LED light radiation on human skin

1 Introduction

Applying LED light sources to lighting is a major advancement in the development of science and technology. Compared with the traditional light source, it is a solid-state semiconductor material, there is no mercury pollution, and it has environmental protection characteristics, which conforms to the trend of energy saving and emission reduction. Since the application of LED lamps to lighting may cause long-term exposure to the human body, it is particularly important to test the human body radiation safety of LED lamps. This experiment is intended to evaluate the effect of an LED light source used in the studio on human skin color and skin barrier function.

2 Methods and materials

2. 1 subject

A total of 30 healthy female volunteers aged 20 to 50 years were selected for this trial. Subject enrollment criteria were: healthy subjects with uniform skin color and age between 20 and 50 years of age; no serious systemic disease, no immunodeficiency or autoimmune disease; no active allergic disease; nearly one month Those who have not used hormonal drugs and immunosuppressive drugs in the whole system; those who did not participate in other clinical trials during the trial; volunteers who participated in the trial, signed informed consent and were able to complete the prescribed contents according to the test requirements; history. Exclusion criteria are as follows: Pregnant or lactating women; have been diagnosed with skin tumors in the past 12 months and are receiving treatment; suffering from atopic dermatitis, eczema, psoriasis or other chronic skin diseases may affect experimental observation; Other pigment-related skin diseases such as vitiligo, malignant melanoma, sun keratosis, etc.; allergic history of cosmetics, fragrances or other skin care products or their ingredients; anti-inflammatory drugs such as corticosteroids, aspen Pirin (more than four days a week), immunosuppressants, etc.; with diabetes, lupus, rheumatoid arthritis, etc.

2. 2 Test related instruments and equipment

2. 2. 1 LED light fixture

The LED lamp (LED50W news light, Beijing Xingguang Group) actually used in the TV studio is used, and the illumination is 2800lx.

2. 2. 2 CM2500d chromameter

CM2500d chromameter (Minolta Camera Co, Japan) is a CIE-recommended instrument for measuring color. The output of the result is represented by L* a* b *. The L* value represents the balance from white to black. The larger the L* value, the closer to white. The smaller the L* value, the closer to black. The a* value represents the balance from red to green, with a positive value indicating the red direction and a negative value indicating the green direction. The b* value represents the balance from yellow to blue, with a positive value indicating the yellow direction and a negative value indicating the blue direction.

2. 2. 3 Maxmeter MX18

Mexameter MX18 (Courage + Khazaka, Germany) is designed for the two main color base melanin and hemoglobin of the skin, and the results are expressed as pigment index (M) and erythema index (E).

2. 2. 4 skin moisture tester Corneometer

Skin moisture tester Corneometer (Courage +Khazaka, Germany), test principle: Since water has a high dielectric constant (approximately 81), much higher than other substances, after the test probe is in contact with the skin, the capacitance value (F The change can reflect the water content in the stratum corneum of the skin. The higher the water content of the stratum corneum, the higher the capacitance; and vice versa.

2. 2. 5 Tewameter TM300

Tewameter TM300 (Courage + Khazaka, Germany) is a standard method for reflecting the barrier function of the stratum corneum. It does not directly indicate the moisture content of the stratum corneum, but indicates the loss of water in the stratum corneum. The higher the TEWL value, the more water lost through the skin, the worse the barrier function of the stratum corneum.

2. 3 methods

2. 3. 1 Irradiation site: Select the non-exposure site—the upper arm flexion side as the irradiation area, each time in the same area.

2. 3. 2 Irradiation dose: The illuminance selected in the test is 2800lx, the irradiation time is 15 minutes, and it is irradiated once a day for 30 days.

2. 3. 3 Determination of skin physiological and physical indicators: Skin L* a* b* value, M, E value, stratum corneum water content and TEWL value were measured before the subject received the LED lamp and after 30 times of irradiation. The above indicators are measured under constant temperature and constant humidity conditions. The room temperature is required to be 25 ° C and the relative humidity is 45% to 55%. The testee enters the test environment 30 minutes in advance and is quiet to be tested. The test site is exposed 10 minutes before the measurement. . The LED light source was measured three times before and after the irradiation, and the average value was taken.

2. 4 statistical processing

The L* a* b* value, M, E value, stratum corneum water content, and TEWL were processed by paired t test before and after the LED light source.

3 Experimental results

3. 1 Subject general situation

A total of 30 subjects were selected for this trial, all female, aged 25 to 48 years, mean age 36.67 years, skin type II-IV.

3. 2 Changes in skin color L* a* b before and after irradiation

The changes in the L* a* b values ​​reflecting the skin color indicators before and after the irradiation were compared (Table 1, Figure 1 - 1, 2, 3), and the results were not statistically compared with the L*, a*, and b values ​​before and after the irradiation. Learning differences (P > 0.05).

3. 3 Changes in skin color M and E before and after irradiation

The changes of M and E values ​​(Table 2, Figure 2) reflecting the skin color index before and after irradiation were compared. The results showed that there were no significant differences in M ​​and E values ​​before and after irradiation (P > 0.05).

3. 4 Changes in water content of the stratum corneum before and after irradiation

There was no significant difference between the two groups (P > 0.05).

3. 5 Changes in water content of TEWL before and after irradiation

The changes in skin TEWL before and after irradiation (Table 4, Figure 4) were compared, and there was no statistical difference between the two (P > 0.05).

3. 6 adverse reactions

During the experiment, three subjects were exposed to the 10th time (2 cases) and the 11th self-reported skin was dry and tingling, but the skin did not have visible erythema, papules, blisters, desquamation, etc. Abnormal reaction. The above discomfort disappeared more than 10 minutes after the end of the irradiation. Three subjects did not withdraw from the experiment.

4 Discussion

Since the application of LED lamps to lighting may cause long-term exposure to the human body, radiation safety testing of LED lamps is particularly important. In Europe, although LEDs are not laser products, Europeans still believe that LED products for lighting have safety hazards, and LEDs in lighting products are required to comply with IECPEN 60825 - 1 "Safety requirements for laser products - Part 1: Equipment classification, requirements and use The requirements of the Standards Chapter 1 - General Requirements. The IEC organization has developed and published IEC 62471: 2006 "Photobiosafety of lamps and lamp systems". China has published the national standard GB20145 - 2006 "Photobiosafety of lamps and lamp systems", causing photochemical hazards to the skin and eyes of LED lamps, near-ultraviolet hazards to the eyes, photochemical hazards of retinal blue light, retinal aphakic photochemical hazards, retinal heat Exposure limits for hazards such as hazards and skin heat hazards are specified. However, the above standards are only measured under laboratory conditions, and there is still a lack of practical research work on human skin.

In this experiment, the LED lamps actually used in the TV studio were used to simulate the actual use of the human skin, and the changes in skin color before and after the irradiation were observed. In order to record the skin color change more accurately, the CM2500d chromameter and the Mexameter MX18 were used to record the color of the skin. The CM2500dchromameter is a CIE-recommended instrument for measuring color. The output of the result is represented by L* a* b*. The L* value represents the balance from white to black. The pure black is 0 and the pure white is 100. The larger the L* value, the more Close to white, the smaller the L* value, the closer to black. The a* value represents the balance from red to green, with a range of + 60 to - 60, with a positive value indicating the red direction and a negative value indicating the green direction. The b* value represents the balance from yellow to blue, with a range of + 60 to - 60, a positive value for the yellow direction and a negative value for the blue direction. MexameterMX18 is designed for the two main color base melanin and hemoglobin of the skin, and the results are expressed as pigment index (M) and erythema index (E). After the LED lamps used in this experiment were continuously irradiated for 30 times, the L*, a*, b, and M and E values ​​of the skin color index did not change significantly. It is suggested that in the case of short-term measurement of this experiment, this LED lamp has no adverse effect on the skin color of human skin.

At the same time, two indicators of skin barrier function and moisturizing function were also determined in the experiment: the water content of the stratum corneum and the transepidermal water loss (TEWL). In the short-term irradiation process of this experiment, the LED light source has the above two indicators. No significant impact.

As a new type of light source, LED is a new way to try out a new product. First of all, we should assess its safety. For LED lights, whether the lighting will cause harm to the human body will be the most concerned issue, and it is also a key factor for the widespread use of LED lights. To evaluate the safety of a new type of light source for human skin requires a long-term accumulation process. In this experiment, only a small dose of short-term irradiation is carried out due to limited conditions, but a preliminary discussion on the safety of human skin by LED light source will be discussed in the future. At work, we will delve into the evaluation of LED safety for long-term exposure.