UV is that part of the sun's radiation that gives the skin a nice brown tint and helps the body produce vitamin D, which is necessary for bones. This vitamin is also involved in the regulation of cell division and even to some extent prevents the development of colon and stomach cancer. Under the action of sunlight, the so-called “hormones of pleasure”, endorphins, are produced.
The human body is able to defend itself against harmful compounds produced under the influence of sunlight. DNA damage is quickly restored thanks to a special system that controls its integrity. And if, nevertheless, a change has occurred in the cell, it is recognized by the immune system as foreign and destroyed. Unfortunately, sometimes the body cannot cope with these damages, especially since UV suppresses the activity of the immune system. That is why, having arrived from warm countries, a person often catches a cold.
At the same time, suppression of the immune system is the main mechanism for treating diseases such as atopic dermatitis and some other skin diseases using ultraviolet radiation.
UV is divided into three spectra depending on the wavelength. Each spectrum has its own characteristics of impact on the human body.
- Spectrum C has a wavelength from 100 to 280 nm. This is the most active range, the rays easily penetrate the skin and cause a destructive effect on the cells of the body. Fortunately, such rays practically do not reach the Earth's surface, but are absorbed by the ozone layer of the atmosphere.
- Spectrum B (UVB) has a wavelength of 280-320 nm and makes up about 20% of all UV radiation that hits the Earth's surface. These rays give redness to the skin during sun exposure. They quickly cause the formation of active compounds in human skin, affecting DNA and causing a violation of its structure.
- Spectrum A, whose wavelength is 320-400 nm, accounts for almost 80% of the UV radiation that hits the human skin. Due to the longer wavelength, these rays have 1000 times less energy than UVB, so they almost do not cause sunburn. They are much less conducive to the production of biologically active substances that can affect DNA. However, these rays penetrate deeper than UVB, and the harmful substances they produce remain in the skin much longer.
Sunburn is primarily skin damage.
The damaging effect of the sun gradually accumulates in the body, and can manifest itself many years later in the form of skin cancer.
Parents, please note: if a child has a sunburn that causes blisters, especially if this happened more than once, the risk of developing melanoma in the future increases several times!
People are protected from the harmful effects of sunlight in different ways. Dark-skinned people have stronger protection, and people with red hair or blondes with blue eyes are more susceptible to the damaging effects of sunlight.
UV can sometimes contribute to the development of itchy rashes. In solar urticaria, itchy, nettle-like rashes develop between 30 minutes and two hours after exposure. Polymorphic light rash - in 1-2 days. This disease is also manifested by itchy rashes at the site of radiation, but they are slower than solar urticaria, and look different. There are other diseases for which UV is a stimulus to develop. For example, lupus erythematosus, rosacea, pellagra (lack of vitamin B3), and others.
Many medications taken by mouth can cause skin rashes when exposed to sunlight. There are some herbs that, after contact with the skin in the sun, cause severe redness and blistering. First of all, these are plants from the umbrella family, among which the strongest is hogweed. In addition, celery, parsley, lime, parsnips and others can cause such dermatitis.
How to protect yourself from the harmful effects of the sun, and at the same time benefit and enjoy it?
The answer is simple: you need to use sunscreen. It is not necessary to take a cream with maximum protection (SPF 50+). The product, which has SPF 15, already provides 80% protection from the sun's rays. This means that part of the UVB will reach the skin and have its positive effect. For sun protection creams to be effective, it is recommended to apply them 20 minutes before sunbathing, and reapply as recommended, usually every 2 hours. But be careful, the use of these drugs does not mean that you can stay under the sun indefinitely. It was this mistake that at one time led to a sharp increase in the incidence of melanoma - due to the lack of obvious sunburn due to protective cream, some sunbathed for too long.
Scientists have found that in order for the body to produce the amount of vitamin D it needs, it is enough to “show the sun” face and hands for 10-15 minutes a day.
Specialists of the EMC Clinic for Dermatovenereology and Allergology-Immunology will gladly give detailed recommendations on sun protection for you and your entire family.
Many of us love to spend time in the sun, someone wants to soak up the warm rays, and someone is chasing a good tan. But is it useful for the body and how does it affect human health? Learn about the benefits and harms of sunlight.
The benefits of sunlight
If you approach this issue wisely, then tanning will positively affect your health. Sun exposure produces vitamin D, which has a beneficial effect on bones and teeth and promotes the absorption of calcium.
Ultraviolet has a beneficial effect on the human immune system. Experts have long proven that the sun slows down the growth of cancer cells. The body receives more oxygen during exposure to sunlight, which improves the functioning of the heart muscle and puts blood pressure in order.
Sun lovers are much less likely to get sick and cope better with stress. When exposed to sunlight, important processes in the body are activated, such as respiration, blood circulation, and metabolism.
Sun damage
If you spend a lot of time in direct sunlight, the risk of skin cancer increases. Do not forget that prolonged exposure to the sun contributes to premature aging of the skin. To avoid such problems, use various oils and creams that will protect the skin from drying out.
We must not forget about burns, the desire to tan quickly and strongly can bring you a lot of inconvenience and harm your health. Be aware of the risk of heatstroke, do not forget that in strong sunshine, your head should be covered.
What is the best time to sunbathe
If you come to rest in warmer climes and want to tan, remember the first 3-4 days you should refrain from long sunbathing. This will only harm you and your skin, and instead of a bronze tan, you can return home with burns.
If we talk about time, we must not forget that in the period from 12:00 to 16:00 the sun is most active and can harm your body. It is worth sunbathing before noon, preferably before 11 o'clock. The most favorable moment is the time from 16:00 to 19:00. During this period, the risk of getting burns is minimal. In addition, the evening sun rays will not affect your vision.
How to protect yourself from sun exposure
Before sunbathing, you should take care of protection. Be sure to purchase a hat with a visor or wide brim to avoid bumps and burns to your face.
Do not forget about sunscreen, which must be applied half an hour before going outside. During this time, the cream will be absorbed and a protective film will form. Apply the product every two hours.
Be mindful of your eyes, protect them with a large visor or sunglasses.
Be careful with your health, remember that in pursuit of a tan you can harm your skin. Enjoy the sun wisely. We wish you good luck and do not forget to press the buttons and
28.07.2015 09:30
They say that faith and a serious intention help move mountains. Therefore, it is not surprising that conspiracies help solve life ...
What is the Sun? On the scale of the visible universe, this is just a tiny star on the outskirts of the galaxy, which is called the Milky Way. But for the planet Earth, the Sun is not just a hot bunch of gas, but a source of heat and light necessary for the existence of all life.
Since prehistoric times, the daylight has been an object of worship, its movement across the firmament has been associated with the manifestation of divine powers. Studies of the Sun and its radiation began even before the adoption of the heliocentric model of Nicolaus Copernicus, the greatest minds of ancient civilizations puzzled over his riddles.
Technological progress has given humanity the opportunity to study not only the processes inside and on the surface of the Sun, but also changes in the Earth's climate under its influence. Statistical data allow us to give a clear answer to the question of what solar radiation is, how it is measured and to determine its impact on living organisms that inhabit the planet.
What is called solar radiation
The nature of solar radiation remained unclear until, at the beginning of the 20th century, the eminent astronomer Arthur Eddington suggested that the source of the colossal solar energy is the thermonuclear fusion reactions that occur in its depths. The temperature near its core (about 15 million degrees) is sufficient for the protons to overcome the force of mutual repulsion and, as a result of the collision, form Helium nuclei.
Subsequently, scientists (in particular, Albert Einstein) discovered that the mass of the Helium nucleus is somewhat less than the total mass of the four protons from which it is formed. This phenomenon is called the mass defect. After tracing the relationship between mass and energy, scientists found that this excess is released in the form of gamma quanta.
When passing the path from the core to the surface of the Sun through the layers of its constituent gases, gamma quanta are crushed and turn into electromagnetic waves, among which is the light visible to the human eye. This process takes about 10 million years. And it takes only 8 minutes to reach the solar radiation of the earth's surface.
Solar radiation includes electromagnetic waves with a wide range and the solar wind, which is a stream of light particles and electrons.
What are the types of solar radiation and its characteristics
At the boundary of the Earth's atmosphere, the intensity of solar radiation is a constant value. The energy of the Sun is discrete and is transferred in portions (quanta) of energy, but their corpuscular contribution is relatively small, so the sun's rays are considered as electromagnetic waves that propagate evenly and rectilinearly.
The main wave characteristic is the wavelength, with which the types of radiation are distinguished: 
- radio waves;
- infrared (thermal);
- visible (white) light;
- ultraviolet;
- gamma rays.
Solar radiation is represented by infrared (IR), visible (VS) and ultraviolet (UV) radiation in the ratio of 52%, 43% and 5%, respectively. The quantitative measure of solar radiation is considered to be energy illumination (energy flux density) - radiant energy arriving per unit of time per unit of surface.
Distribution of solar radiation over the earth's surface
Most of the radiation is absorbed by the earth's atmosphere and heats it up to the usual temperature for living organisms. The ozone layer transmits only 1% of ultraviolet rays and serves as a shield against more aggressive short-wave radiation.
The atmosphere absorbs about 20% of the sun's rays, scatters 30% in different directions. Thus, only half of the radiant energy, called direct solar radiation, reaches the earth's surface.
Several factors influence the intensity of direct solar radiation: 
- the angle of incidence of the sun's rays (geographical latitude);
- distance from the point of impact to the Sun (season);
- the nature of the reflective surface;
- transparency of the atmosphere (cloudiness, pollution).
Scattered and direct radiation make up the total solar radiation, the intensity of which is measured in calories per unit surface. It is clear that solar radiation has an effect only in the daytime and is distributed unevenly over the earth's surface. Its intensity increases as it approaches the poles, however, snow reflects a large proportion of radiant energy, as a result of which the air does not heat up. Therefore, the total indicator decreases as you move away from the equator.
Solar activity shapes the Earth's climate and affects the life processes of the organisms that inhabit it. On the territory of the CIS countries (in the northern hemisphere), diffuse radiation prevails in the winter season, and direct radiation in the summer.
Infrared radiation and its role in the life of mankind
Solar radiation is represented predominantly invisible to the human eye. It is it that heats the earth's soil, which subsequently gives off heat to the atmosphere. Thus, the temperature and habitual climatic conditions are optimal for life on Earth.
In addition to the Sun, all heated bodies are sources of infrared radiation. All heating devices and devices that allow you to see more or less heated objects in conditions of poor visibility work according to this principle.
The fact that a person is not able to perceive infrared light does not reduce its effect on the body. This type of radiation has found application in medicine due to the following properties: 
- expansion of blood vessels, normalization of blood flow;
- an increase in the number of leukocytes;
- treatment of chronic and acute inflammation of internal organs;
- prevention of skin diseases;
- removal of colloid scars, treatment of non-healing wounds.
Infrared thermographs allow timely detection of diseases that cannot be diagnosed using other methods (blood clots, cancerous tumors, etc.). Infrared radiation is a kind of "antidote" against negative ultraviolet radiation, therefore its healing properties are used to restore the health of people who have been in outer space for a long time.
The mechanism of action of infrared rays is not fully understood and, like any type of radiation, if used improperly, can be harmful to human health. Treatment with infrared rays is contraindicated in the presence of purulent inflammation, bleeding, malignant tumors, insufficiency of cerebral circulation and the cardiovascular system.
Spectral composition and properties of visible light
Light beams propagate in a straight line and do not overlap each other, which raises a fair question why the world around us strikes with a variety of different shades. The secret lies in the basic properties of light: reflection, refraction and absorption.
It is known for certain that objects do not emit light, it is partially absorbed by them and reflected at different angles depending on the frequency. Human vision has evolved over the centuries, but the retina of the eye can only perceive a limited range of reflected light in the narrow gap between infrared and ultraviolet radiation.
The study of the properties of light has given rise not only to a separate branch of physics, but also to a number of non-scientific theories and practices based on the effect of color on the mental and physical state of the individual. Using this knowledge, a person decorates the surrounding space in the most pleasing color for the eyes, which makes life as comfortable as possible.
Ultraviolet radiation and its effect on the human body
The ultraviolet spectrum of sunlight consists of long, medium and short waves, which differ in physical properties and the nature of the impact on living organisms. Ultraviolet rays, which belong to the long-wave spectrum, are mainly scattered in the atmosphere and do not reach the earth's surface. The shorter the wavelength, the deeper the ultraviolet penetrates into the skin.
Ultraviolet radiation is essential for sustaining life on Earth. UV rays have the following effects on the human body:
- saturation with vitamin D, necessary for the formation of bone tissue;
- prevention of osteochondrosis and rickets in children;
- normalization of metabolic processes and synthesis of beneficial enzymes;
- activation of tissue regeneration;
- improvement of blood circulation, expansion of blood vessels;
- increased immunity;
- removal of nervous excitement by stimulating the production of endorphins.
Despite the long list of positive qualities, sunbathing is not always effective. Prolonged exposure to the sun at unfavorable times or during periods of abnormally high solar activity nullifies the beneficial properties of UV rays.
Ultraviolet irradiation in high doses has the opposite result as expected: 
- erythema (reddening of the skin) and sunburn;
- hyperemia, puffiness;
- increase in body temperature;
- headaches;
- dysfunction of the immune and central nervous systems;
- loss of appetite, nausea, vomiting.
These signs are symptoms of sunstroke, in which the deterioration of a person's condition can occur imperceptibly. Procedure for sunstroke:
- move the person from the area exposed to direct sunlight to a cool place;
- put on your back and raise your legs to an elevation to normalize blood circulation;
- rinse your face and neck with cool water, preferably make a compress on your forehead;
- provide the opportunity to breathe freely and get rid of tight clothing;
- for half an hour, give a drink of a small amount of clean cold water.
In severe cases, with loss of consciousness, it is necessary to call an ambulance team and, if possible, bring the victim to his senses. Medical assistance to the patient consists in the emergency administration of glucose or ascorbic acid intravenously.
Safe tanning rules
UV rays stimulate the synthesis of a special hormone melanin, with the help of which human skin darkens and takes on a bronze hue. Disputes about the benefits and harms of tanning have been going on for decades.
It has been proven that sunburn is a protective reaction of the body to ultraviolet radiation, and excessive sunbathing increases the risk of malignant tumors.
If the desire to pay tribute to fashion prevails, you need to understand what solar radiation is, how to protect yourself from it and follow simple recommendations:
- sunbathe gradually exclusively in the morning or evening;
- do not stay in direct sunlight for more than an hour;
- apply protective agents to the skin;
- drink more pure water to avoid dehydration;
- include in the diet foods that contain vitamin E, beta-carotene, tyrosine and selenium;
- limit the consumption of alcoholic beverages.
The reaction of the body to ultraviolet radiation is individual, so the time for sunbathing and their duration should be selected taking into account the type of skin and the state of human health.
Tanning is highly contraindicated for pregnant women, the elderly, people with skin diseases, heart failure, mental disorders and in the presence of malignant tumors.
In the 80s of the XIX century in America and Europe, a tanned body was considered beautiful and desirable, which many people aspired to. This gave scientists a lot of reasons and materials for research. They found that skin changes, called age-related, for the most part do not depend on the number of years a person has lived, but on the harmful effects of ultraviolet radiation, which is responsible for the appearance of a tan.
So there was a theory of photoaging - premature fading of the skin under the influence of UV radiation. It is confirmed by the data that the skin of the inhabitants of the southern countries ages faster than those who are not spoiled by the sun. In addition, open areas of the body that are not protected by clothing undergo various changes faster.
Mechanism of photoaging
Penetrating into the skin, UV rays meet the natural UV filter - melanin, which blocks more than 90% of UV radiation. Thus, sunburn is nothing more than a reaction of the skin to the traumatic effect of solar radiation. Now many people know that prolonged exposure to ultraviolet radiation contributes to the development of melanoma, skin cancer, accelerates aging and the appearance of wrinkles.
Types of UV radiation
Types of sunbeams
Ultraviolet radiation is divided into three components: rays A, B and C (UVA, UVB, UVC rays, respectively). As sunlight passes through the Earth's atmosphere, the most dangerous UVC rays and about 90% of mid-range UVB rays are absorbed by ozone, oxygen and carbon dioxide. Therefore, the radiation that reaches a person contains a large amount of ultraviolet UVA and a small amount of UVB.
Why UVB rays are dangerous
UVB rays produce melanin, cause photoaging of the skin, and stimulate the development of most types of skin cancer, but they are blocked by the protective substances found in sunscreens.
Why are UVA rays dangerous?
UVA rays are less active than UVB in stimulating the development of many types of skin cancer, but they contribute to the formation of melanoma - the most dangerous type of skin cancer. In addition, this radiation is not blocked by many solar filters, so the main protection against it is clothing.
Why is ultraviolet dangerous to humans:
- it reduces the production of collagen - a protein of the connective tissue of the body, due to the lack of which the skin loses its elasticity and wrinkles appear on it;
- it provokes coarsening and thickening of the stratum corneum of the skin, as a result of which it becomes dry, dull and rough;
- it provokes vascular changes, violation of skin pigmentation, as well as the development of neoplasms.
About the benefits of the sun
A place under the sun
Despite the danger of ultraviolet radiation for the body, in small doses it can be beneficial. To do this, it is enough just a few times a week to expose your face or hands to sunlight for 10-15 minutes.
Healing ultraviolet:
- under the influence of ultraviolet radiation, vitamin D is synthesized in the body, which regulates calcium metabolism and serves as a building material for bone tissue;
- sunlight activates the immune system, increases the body's resistance to viruses and infections;
- the sun has a positive effect on the human nervous system, increasing the production of endorphins (hormone of joy) and thereby improving mood;
- in small doses, ultraviolet prevents the occurrence of diseases of the cardiovascular system, musculoskeletal system (osteochondrosis, arthritis) and respiratory organs (bronchitis, rhinitis), dermatological diseases (psoriasis, neurodermatitis, eczema, etc.), cerebrovascular insufficiency.
How to sunbathe
You need to start sunbathing little by little, in the morning and evening hours, spending 10 to 15 minutes in the sun with breaks. Both dark and pale-skinned people should definitely use sunscreen that matches their skin type and with the right SPF. Apply them to the skin should be 20-30 minutes before going outside.
Owners of skin that is particularly sensitive to sunlight should stay in the shade as often as possible and use products with the highest SPF factor (Sun Protection Factor). Your eyes and lips also need sun protection, so use sunscreen around your eyes, lip balm with SPF, and wear sunglasses when you go out.
Peelings are considered an effective means of eliminating
symptoms of photoaging of the skin. They have exfoliating
action, as well as restore skin tone and beauty.
Elena Kobozeva, dermatovenereologist, cosmetologist:“Ultraviolet is the main factor in skin aging. With excessive solar exposure, it provokes the so-called fine-wrinkled type of aging. The skin becomes like a shriveled baked apple, covered with a network of small wrinkles. In addition, ultraviolet radiation provokes the formation of age spots. This is especially noticeable at the age of over 35 years. Therefore, in the summer it is necessary to constantly protect the skin with sunscreens with a high protection factor.
Expert: Elena Kobozeva, dermatovenereologist, cosmetologist
Katerina Kapustina
Prominence on the surface
The radiation from the sun, which is known as sunlight, is a mixture of electromagnetic waves ranging from infrared (IR) to ultraviolet (UV) rays. It includes visible light, which lies between IR and UV in the electromagnetic spectrum.
Velocity of propagation of electromagnetic waves
All electromagnetic waves (EM) propagate at a speed of approximately 3.0x10*8 m/s in a vacuum. Space is not a perfect vacuum, it actually contains low concentrations of particles, electromagnetic waves, neutrinos and magnetic fields. Since the average distance between the Earth and the Sun is more than 149.6 million km, it takes about 8 minutes for the radiation to reach the Earth. The sun shines not only in the IR, visible and UV range. Basically, it emits high-energy gamma rays.
However, gamma-ray photons travel a long way to the surface, they are constantly absorbed by the solar plasma and re-emitted with a change in their frequency.
By the time they reach the surface, gamma ray photons are in the IR, visible, and UV spectra. Infrared radiation is the heat that we feel. Without it and visible light, life on Earth would be impossible. During solar flares, it also emits X-rays. When the Sun's electromagnetic radiation reaches the Earth's atmosphere, some of it is absorbed while the rest reaches the Earth's surface.
In particular, UV radiation is absorbed by the ozone layer and re-emitted as heat, which leads to heating of the stratosphere.
