A brief discussion on the application of LED in dermatology

Using light to treat human diseases is a very old method. As early as thousands of years ago, China and other countries used sunlight to treat diseases. As a new type of light source, LED is gradually being used in medicine and playing a positive role as its biological effects are gradually recognized by people. This article will explain and describe the application of LED in dermatology in detail.

　　1. Optical parameters affecting LED biological effects

　　The biological effect of LED depends on different optical parameters, including different wavelengths, flow rates, intensities, irradiation time, continuous waves or pulse waves, as well as the number of clinical treatments and treatment intervals. Different wavelengths can reach different locations of skin tissue (as shown in Figure 1). Generally speaking, the longer the wavelength, the stronger the penetration ability. At 400nm, the penetration distance of skin tissue does not exceed 1mm, the penetration distance of 514nm is about 0.5mm~2mm, and the penetration distance of 630nm is about 1mm~6mm. At the same time, light of different wavelengths can be absorbed by different color bases in tissues. In clinical practice, red light (630nm~700nm) is often used to treat deep skin tissue structures, such as sebaceous glands; blue light is used in photodynamic therapy to treat skin lesions located in the epidermis; if you want to reach the dermis of the skin, you need a longer wavelength, such as a wavelength of 660nm, which can reach the reticular layer of the dermis and thus exert an effect on the skin fibroblasts in the dermis, which is also one of the principles of LED light sources for photorejuvenation.

　　2. Application of LED in Dermatology

　　1. Photorejuvenation

　　Photorejuvenation is defined as a non-ablative skin rejuvenation treatment using continuous intense pulsed light at low energy density. In just a few years since its introduction in 2000, photorejuvenation has rapidly spread across the country and has been widely used in major cities. It has now become one of the main means to improve skin photoaging. This technology can significantly improve skin wrinkles, rough texture, irregular pigmentation, and enlarged pores, and has been recognized by many technical professionals and beauty seekers. The characteristic histological changes of skin photoaging are elastic fiber degeneration and collagen fiber maturation disorders in the dermal matrix, which lead to sagging and wrinkles on the skin.

　　Studies have found that after visible light to near-infrared LED light penetrates the skin epidermis and reaches the skin dermis, it promotes the regeneration and rearrangement of elastic fibers and collagen fibers through photothermal and photochemical effects, thereby achieving the effect of reducing skin wrinkles and increasing elasticity.

　　2. Prevent or treat post-inflammatory hyperpigmentation

　　Pigmentation of the skin after inflammation is a common and difficult-to-avoid phenomenon in physical and chemical skin cosmetology, especially in Asian populations. For example, in order to reduce the degree of skin pigmentation after laser treatment, patients are generally advised to avoid seasons with strong ultraviolet rays, avoid sun exposure, and apply sunscreen, etc. However, it is still difficult to completely avoid pigmentation after inflammation. In recent years, studies have found that 660nm LED light can prevent and even treat this kind of skin pigmentation after inflammation, which will be a new research hotspot in the skin beauty industry.

　　3. Promote wound healing

　　LED lights of various wavelengths from visible to near infrared can promote the growth of epithelial cells after trauma and promote the healing of wounds. At the same time, they also have a good therapeutic effect on the healing of chronic ulcers in the lower limbs of diabetic patients.

　　4. Reduces Inflammation

　　A series of studies have shown that LED has anti-inflammatory effects. Studies have found that 635nm LED light can inhibit the release of inflammatory mediators - prostaglandin E2 (PGE2) by gingival fibroblasts, thereby reducing the inflammatory response of the gums. If LED light is used in advance before pulse dye laser treatment of skin photoaging, it can reduce the discomfort of skin erythema, swelling and pain caused by dye laser. Using LED light source in advance before radiotherapy for breast cancer patients can reduce the side effects of radiotherapy.

　　5. Scar prevention

　　Keloid is a skin disease that affects beauty clinically and is difficult to treat. It is caused by excessive proliferation of connective tissue after skin damage. Patients often have a scar-prone physique. Clinically, it starts as a small and hard red papule, which slowly grows and produces round, oval or irregular scars that are higher than the skin surface and stretch outward like crab feet. The skin is smooth and shiny, and may be accompanied by pain, itching and other discomforts. Clinical treatment is difficult and the effect is not ideal. Studies have found that LED can significantly improve patients' discomfort such as pain and itching, flatten scars, and has the advantage of being non-invasive.

　　6. Other functions

　　In addition, LED can also be used as a phototherapy device without ultraviolet rays, for photodynamic therapy, treatment of hair loss, reduction of skin damage after ultraviolet radiation, etc.

　　In short, as a new type of light source, LED has been gradually applied to dermatology. With the continuous innovation of LED lamps and the research on the mechanism of LED biological effects in medicine, the application of LED in dermatology will have unlimited prospects. At the same time, LED has high safety and can be used as a home medical device.