Ultraviolet therapy

Therapeutic effect

The biological effects of ultraviolet light are the basis of its clinical therapeutic effects. The biological effects of ultraviolet light have been described in detail in the relevant chapters, and the spectrum of their action is shown in Figure 4-1. This section only briefly describes the mechanism of action of clinical application of UV in the treatment of skin diseases.

(1) bactericidal effect

Ultraviolet irradiation of infected wounds can directly kill pathogens or change the living environment of microorganisms and inhibit their growth and reproduction. The bactericidal effect of ultraviolet light is related to its wavelength, and the ultraviolet sterilizing ability of different wavelengths is different. Those with a wavelength of 300 nm or more have almost no sterilizing ability, and those with a wavelength of 300 nm or less have a bactericidal power with a shortening of the wavelength, and the strongest of 250 to 260 nm is later, and this is called a ultraviolet sterilizing curve (Fig. 4-1). And various bacteria have different sensitivity to different wavelengths of ultraviolet light, and Staphylococcus aureus is most sensitive to 253.7nm ultraviolet light. In addition, ultraviolet irradiation must reach a certain irradiation intensity to have an effective bactericidal effect. Studies have shown that the negative quadratic intensity of 3 �� 10 cubic erg��cm can inhibit bacterial growth, and each bacterium receives 7.6��10 When the action of the six-th power photon is used, the growth is significantly suppressed. Danish physician Niels Finsen used artificial UV to heal lupus and skin tuberculosis, and he won the 1903 Nobel Prize in Medicine.

(2) promote the synthesis of vitamin D

It is an important physiological action after ultraviolet radiation on the skin, and the peak wavelength is at 280 nm (Fig. 4-1). This not only has preventive and therapeutic effects on rickets and rickets, but also has a positive effect on preventing osteoporosis in the elderly.

(3) Promoting local blood circulation

Vascular relaxation in the ultraviolet irradiation area and improvement of local nutritional status can accelerate the clearance of inflammatory mediators, and the hypoxia and acidosis are alleviated. The factors that cause erythema reaction by ultraviolet light can improve local blood circulation. The erythema formation curve has two peak wavelengths (Fig. 4-1), which are located at 297 nm and 250 to 260 nm, respectively. In addition, blue-violet light can increase skin circulation by 100%, and most of the ultraviolet light sources are accompanied by a certain amount of blue-violet light. Usually, the improvement of blood circulation caused by ultraviolet erythema reaction is delayed, and blue-violet light is an immediate effect.

(4) analgesic effect

The erythema treatment has obvious analgesic effect. The pain threshold is increased in the irradiation area, and the sensation time is prolonged, which has a good alleviation effect on inflammatory and non-inflammatory pain. 50% of the ultraviolet light at 350nm can penetrate deep into the free nerve endings, making these sensory nerve endings enter the inter-ecological (conduction pause) and the pain is weakened.

(5) Anti-inflammatory effect

The above bactericidal action, promoting local blood circulation and analgesic effects are all beneficial to anti-inflammatory effects. In addition, UV can mobilize and strengthen the body's immune function, such as UVB and UVA can stimulate the function of the reticuloendothelial system; skin protein denaturation (addition of antigen) after UV irradiation leads to the increase of body complement and lectin; Under the action of ultraviolet rays, the body's opsonization is increased, which can promote phagocytosis. Therefore, the anti-inflammatory effect of ultraviolet rays is a combined effect of the above factors.

(6) Promoting wound healing

Ultraviolet light has the effect of promoting cell growth, division and proliferation, improving blood circulation, improving tissue cell nutrition and regeneration conditions, etc., all of which are beneficial to wound healing. It can be used clinically to treat various wounds, wounds and skin ulcers that have not healed.

(7) Pigmentation

It is beneficial to enhance the skin's light fastness and improve the resistance to ultraviolet rays. It is also a mechanism for treating vitiligo. Including both immediate and delayed, the former occurs immediately after irradiation, and light of 300-700 nm can be caused, which is the result of melanin oxidation and melanin distribution in keratinocytes. The most effective cause of delayed pigmentation is 254 nm UVC or 340 nm UVA.

(8) skin keratin thickening

Ultraviolet radiation can promote skin keratin thickening, up to 2 to 3 times thicker, thereby enhancing the skin's barrier function, reducing harmful chemicals and allergens into the skin. In addition, a certain intensity of ultraviolet radiation on the body surface can make the skin pigmentation, thicken the keratin, and enhance the skin barrier defense ability; it can also enhance the physical fitness, improve the adaptability to environmental changes and resistance to certain diseases, such as can be used for prevention and treatment. Pressure sores, folliculitis, rickets, etc.

(9) desensitization

Under multiple UV exposures, the body produces a small amount of histamine, which continuously enters the bloodstream from the skin and stimulates the production of histidine. When the latter has sufficient amount, it can decompose excessive histamine in the blood during allergic reactions. To desensitization. Therefore, it can be used clinically to prevent and treat type I allergic diseases as the main pathogenesis. This year's study proves that ultraviolet radiation also has a preventive effect on type IV allergic reactions, such as contact dermatitis. The most effective wavelength is 297 nm UVB, but the effect of UVA is not obvious.

(10) Immunomodulatory effects

When human skin is exposed to ultraviolet radiation, even if the radiation dose is relatively low, it will change the morphology and function of the epidermal Langerhans cells, induce specific inhibitory T lymphocytes, or induce immunosuppression of the body, affecting keratinocytes. Immunological activity. DNA and urinary acid are the main color bases for immunological changes induced by ultraviolet radiation.

(11) Other special people such as miners and athletes who use ultraviolet radiation can enhance physical strength, reduce fatigue and improve endurance. Ultraviolet light also significantly promotes the absorption of subcutaneous ecchymoses and promotes thrombolytic effects. It can be used to prevent and treat acne, frostbite, dystrophic ulcers, and early thrombotic occlusive vasculitis. In addition, it has been reported that UVB irradiation can significantly alleviate the symptoms of pruritus in AIDS patients, which is conducive to the improvement of patients' quality of life. Ultraviolet rays also have the effect of treating tumor cell apoptosis.