Irradiation of the skin with ultraviolet rays

Ultraviolet irradiation is a therapeutic application of UV radiation.

Like many physiotherapeutic methods used in cosmetology, UV irradiation was initially used for therapeutic purposes (including treatment of acne, alopecia, vitiligo, etc.) and only after a while they began to be used for aesthetic purposes (as an alternative to natural tan) .

Ultraviolet (UV) radiation was discovered in 1801 by I. Ritter, W. Herschel, and W. Wallallon. In the first half of the XX century. In the spectrum of the optical range, reaching to the earth's surface, it occupied slightly more than 1%. However, over the past 50 years, due to unfavorable environmental conditions and thinning of the stratospheric ozone layer, this figure has increased to 3-5%.

UV rays are absorbed by different layers of the skin and penetrate into the tissues to insignificant depths - 0.1-1.0 mm. The processes of absorption and permeability of UV rays depend on such skin properties as the thickness of the epidermis, its pigmentation, the degree of hydration and blood supply, the content of carotenoids and uric acid. A certain value has a wavelength. UV rays of the predominantly "C" (CUF) region with a wavelength of less than 280 nm are absorbed by the stratum corneum of the epidermis.

UV rays "B" (280-320 nm) penetrate 85-90% in all layers of the epidermis, and 10-15% of these rays reach the papillary layer of the dermis. At the same time, UV rays with a wavelength of more than 320 nm, i.e. Region "A", are absorbed and penetrate into the deeper layers of the dermis, reaching its reticular layer. In the white race, UV rays pass deeper, in blacks they are absorbed by the surface layers of the skin due to the presence of a large amount of melanin pigment in it.

UV radiation is an indispensable factor for the normal functioning of the human body. Undoubtedly, the most pronounced direct effect it has on the skin. However, due to complex neuro-reflex and neurohumoral reactions, UV radiation significantly affects the condition of many internal organs, metabolic processes, hematopoiesis, adaptive reactions, which is the basis of its therapeutic and preventive use.

In recent years, many experts have talked about the adverse effect of UV radiation, including artificial sources, on the human body, especially on the skin.

Long-wave radiation

Ultraviolet rays of the long-wave range (DUV-rays) stimulate the transport of granules of melanin from the soma located among the cells of the basal layer of the epidermis of melanocytes along numerous processes diverging in different directions, which causes the pigmentation (quick tanning) of the skin. Melanin appears after 2 hours, but does not protect the skin from sunburn. Melanin is a powerful antioxidant and suppresses the activation of lipid peroxidation by toxic metabolites of oxygen. The maximal melanin-transporting action is irradiation with a wavelength of 340-360 nm.

Photodestruction products covalently bind to skin proteins and form antigenic peptides that come into contact with Langerhans cells of the supra-basal layer of the epidermis. These cells, which possess antigen-presenting properties, move to the dermis and trigger the formation of a cellular immune response. The start-up of the above described processes occurs after 15-16 hours and reaches a maximum after 24-48 hours after the initiation of the antigenic peptide. Depending on the state of the organism and the duration of irradiation, the composition of the cellular population of the immune response can vary significantly. Repeated exposure to photo-destructive antigenic peptides increases the number of clones of T-dimfocytes recognizing them. Consequently, regular DUV irradiation, in addition to expanding the antigen-recognizing "repertoire" of T-lymphocytes, increases the level of immunorefection of the organism to the effects of unfavorable environmental factors. At the same time, prolonged DUV irradiation results in the almost complete disappearance of Langerhans cells from the epidermis and the weakening of the presentation of the products of photodestruction by patrolling T-lymphocytes of the epidermis. Penetrating into the dermis, DuPH-induced antigenic peptides activate antigen-specific T-suppressors that block the initiation of T-helpers, which can cause blast transformation of the cellular elements of the skin.

Therapeutic effects: melanin transporting, immunostimulating.

Medium-wave radiation

Different doses of ultraviolet radiation determine the unequal probability of the formation and manifestation of therapeutic effects. Based on this, the effect of medium-wavelength ultraviolet radiation in sub-erythemic and erythemic doses is considered separately.

In the first case, the SUF radiation within the range of 305-320 nm stimulates the decarboxylation of tyrosine followed by the formation of melanin in melanocytes. The intensification of melanogenesis leads to compensatory activation of the synthesis of adrenocorticotropic and melanin-stimulating hormones of the pituitary gland, which regulate the secretory activity of the adrenal glands.

When medium-wave ultraviolet rays (280-310 nm) are irradiated with lipids of the surface layers of the skin, vitamin D synthesis is triggered, which regulates the excretion of calcium and phosphate ions in the urine and accumulation of calcium in the bone tissue.

When the intensities of the SUF radiation (erythemic dose) increase, the products of photodestruction-antigenic peptides-are transported by the Langerhans cells from the epidermis to the dermis by sequential recruitment and proliferation of T-lymphocytes, causing the formation of immunoglobulins A, M and E, and granulation of mast cells basophils and eosinophils with histamine release , heparin, platelet activation factor FAT) and other compounds regulating the tone and permeability of the skin vessels. As a result, biologically active substances (plasmakinins, prostaglandins, arachidonic acid derivatives, heparin) and vasoactive mediators (acetylcholine and histamine) are released in the adjacent layers of the skin and vessels. Through molecular receptors, they activate ligand-guided ion channels of neutrophils and lymphocytes and, by activating the endothelial hormones (endothelin, nitric oxide, superoxide of nitrogen, hydrogen peroxide), significantly increase the vascular tone and local blood flow. This leads to the formation of a limited skin hyperemia - erythema. It occurs after 3-12 hours from the moment of irradiation is saved up to 3 seconds. Has clear boundaries and a smooth red-violet color. The further development of the reaction is interrupted due to the increase in the dermis of the content of cis-urocanic acid, which has a pronounced immunosuppressive effect. Its concentration reaches a maximum after 1-3 hours and returns to normal after 3 weeks after irradiation. Erythema leads to dehydration and reduction of edema, a decrease in alteration, suppression of the infiltrative-exudative phase of inflammation in segmentally associated with the area of irradiation of the underlying tissues and internal organs.

The reflex reactions that arise during SUF irradiation stimulate the activity of almost all the systems of the body. Activation of the adaptive-trophic function of the sympathetic nervous system and restoration of disturbed processes of protein, carbohydrate and lipid metabolism in the body takes place. The sensitivity of the skin of a healthy person to SUF radiation depends on the time of the previous irradiation and to a lesser extent on the hereditary pigmentation. In the spring, sensitivity increases, and in autumn it decreases. The skin of various areas of the human body has an unequal sensitivity to ultraviolet radiation. The maximum sensitivity is fixed in the upper parts of the back and lower abdomen, and the minimum - on the skin of the hands and feet.

Therapeutic effects: melaninsynthetic, vitamin-forming, trophostimulating, immunomodulating (suberythmic doses), anti-inflammatory, desensitizing (erythemic doses).

Shortwave radiation

Short-wave irradiation is a therapeutic application of short-wave ultraviolet radiation. It causes denaturation and photolysis of nucleic acids and proteins. The resulting fatal mutations with the ionization of atoms and molecules lead to inactivation and destruction of the structure of microorganisms and fungi.

Therapeutic effects: bactericidal and mycicidal.

With a schematic representation of the histological and biochemical reactions occurring in the epidermis and the skin itself under the influence of UV-irradiation, we can talk about the following changes. In the skin there are many so-called chromophores - molecules that absorb a significant amount of UV radiation with certain wavelengths. These include, first of all, protein compounds and nucleic acids, trans isomer of urocanic acid (absorption of UV radiation in the spectrum of 240-300 nm), deaminated histidine, melanin (350-1200 nm), aromatic amino acids of protein molecules in the form of tryptophan and tyrosine (285-280 nm), nitrogenous compounds of nucleic acids (250-270 nm), porphyrin compounds (400-320 nm), etc. Under the influence of UV absorption in chromophore substances of the epidermis and dermis, the most pronounced photochemical reactions develop, the energy of which leads to the image vaniyu active oxygen species, radicals, hydrogen peroxide and other free radical compounds. In turn, these substances react with DNA molecules and other protein structures, which can lead to undesirable consequences and changes in the genetic apparatus of the cell.

Thus, with the maximum absorption of UV radiation, proteins and nucleic acids are primarily affected. However, as a result of free radical reactions, lipid structures of the epidermis and cell membranes are damaged. UV radiation increases the activity of metal proteases, which can cause degenerative changes in the intercellular substance of the dermis.

As a rule, unfavorable effects most often arise from the effect of UV radiation from regions "C" (280-180 nm) and "B" (320-280 nm), causing the most severe reactions in the epidermis. DUV radiation (region "A" - 400-320 nm) has a milder effect, mainly on the dermis. Histological studies on unfavorable changes in skin cells under the influence of UV irradiation in the form of dyskeratosis, degranulation of mast cells, reduction of Langerhans cells, inhibition of DNA and RNA synthesis, are described in great detail by dermatologists and cosmetologists who study photoaging of the skin.

These changes in the morphological state of the skin, as a rule, occur with excessive undamaged irradiation in the sun, in solariums and when using artificial sources. Degenerative shifts in the epidermis and actually in the skin at the same time are manifested by an increase in the mitotic activity of the germ layer of the epidermis, acceleration of keratinization processes. This is expressed in the thickening of the epidermis, the appearance of a large number of completely keratinized cells. The skin becomes dense, dry, easily folds into wrinkles and prematurely ages. At the same time, this skin condition is temporary.

Of course, there is a positive effect of UV rays on the body. Under their action there is a synthesis of vitamin D, so necessary for the body to assimilate calcium and phosphorus, the formation and restoration of bone tissue. With some skin diseases, UV irradiation has a therapeutic effect and is called heliotherapy. But in this case it is necessary to follow the recommendations of the doctor. Skin Reaction to UV Irradiation:

• thickening of the stratum corneum and reflection or absorption of light by keratin;
• production of melanin, the pigment granules of which dissipate the absorbed solar energy;
• formation and accumulation of urocanic acid, which, passing from the cis-form to the trans-form, promotes neutralization of energy;
• selective cumulation of carotenoids in the dermis and hypoderma, where beta-carotene acts as a stabilizer of cell membranes and an absorber of oxygen radicals formed upon damage to porphyrins by UV rays;
• production of superoxide dismutase enzymes, glutathione peroxidase and others, neutralizing oxygen radicals;
• restoration of damaged DNA. And the normalization of the replication process.

In the event of a disruption in the function of protective mechanisms, depending on the intensity, wavelength and penetrating ability of the sun's rays, it is possible to damage tissues of varying degrees - from mild erythema, sunburn to the formation of cutaneous neoplasms.

Negative factors of exposure to UV radiation:

• burn;
• damage to the eyes;
• photo aging;
• danger of oncological diseases.

Recommendations for receiving UV irradiation:

• Before sunburn, it is necessary to prepare skin of the face and body; remove makeup, take a shower, use a scrub or gommage.
• Avoid the application of perfume, cosmetic products (except professional means for stimulation of melanogenesis, protection and moistening)
• Take into account the intake of drugs (antibiotics, sulfonamides and other skin sensitizing agents to UVD).
• Use eye protection glasses, cream to protect the red lip rims.
• It is recommended to protect hair from direct exposure to UV rays.
• It is recommended to avoid direct exposure to UV rays on the nipple area of the mammary gland and genitals.
• After UV irradiation, it is recommended to take a shower and apply a special moisturizer. The use of scrub after insolation is not justified.
• In the presence of dermatological diseases it is necessary to consult a patient with a dermatologist.

The distance from the patient's body to the source of integral UV radiation is 75-100 cm; DUV + SUF radiation - 50-75 cm; DUV radiation - not less than 15-20 cm.

Dosing procedures are carried out by different methods: by bio-dose, by intensity (density) of energy in J / m ² or by the duration of irradiation specified in the irradiator's instructions and chosen taking into account the sensitivity of the skin to UV radiation.

During the period of irradiation, especially in the winter-spring season, it is recommended to take multivitamins, especially vitamin C. It is not shown that UV irradiation is carried out continuously, during the whole year.

Between courses of irradiation in solariums or fotariums it is necessary to make intervals for the restoration of the optical properties of the skin and normalization of the organism's activity. Control of disinfection of sun beds, floor coverings, protective glasses.