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The sun has some beneficial effects on the skin. It stimulates the production of endorphins, which affect the mood, by affecting the secretion of melatonin and increasing the oxygen concentration in tissues, it improves mental and physical performance and activates the synthesis of vitamin D, necessary for the proper functioning of the calcium-phosphate metabolism. On the other hand, excessive sun exposure can be harmful to health, cause sunburn and premature aging of the skin, increase the risk of cancer, as well as damage eyesight and be allergic.
Healthy skin defends itself against light damage through a variety of mechanisms. The effectiveness of this defense is indicated, among others, by skin pigmentation and the color of hair and eyes (blue-eyed or green-eyed blondes and people with red hair are especially vulnerable). These features determine the skin’s ability to receive a certain dose of UV rays.
Depending on the intensity of the skin color, the following division is used:
– Phototype I – no tan – Celtic race,
– Phototype II – weak tan – Caucasian,
– Phototype III – medium tan – Caucasian,
– Phototype IV – dark tan – Caucasian,
– Phototype V – naturally dark skin – dark Caucasian race,
– Phototype VI – black skin – negroid race.
The phototype of human skin depends on the concentration of melanin in the body, which colors not only the skin, but also the hair and the iris of the eye. Melanin in the skin protects its deeper layers from the harmful effects of UV rays, which are part of solar radiation, i.e. UVA, UVB and UVC. UVA radiation, which accounts for 95% of UV rays reaching the Earth, damages collagen fibers in the skin, which accelerates the aging process, and long-term exposure to high doses of this radiation may lead to neoplastic changes and the occurrence of photochemical cataracts. UVB rays enable the synthesis of vitamin D, necessary for the construction and regeneration of bones, but they also have adverse effects – they contribute to the formation of erythematous changes and allergic symptoms. Long-term exposure to these rays is the best documented risk factor for skin cancers – melanoma and other, less aggressive ones. On the other hand, UVC radiation can damage the DNA chains responsible for the formation of mutations, which can result in skin cancer. Fortunately, it is almost completely blocked by the ozone layer of the atmosphere. Photodermatoses can also be caused by rays emitted by artificial light sources, especially fluorescent lamps used to illuminate rooms, quartz lamps used in medicine and bactericidal lamps used for disinfecting laboratory and hospital rooms.
Below are some of the most common diseases caused by overexposure to UV rays.
Sunburn and solar skin aging
The most common of them are Sun burns. Erythematous changes appear several hours after exposure, are most severe after 14-20 hours and have features of XNUMXst or XNUMXnd degree burns (with the presence of blisters with serum fluid). Too frequent and prolonged contact with the sun, especially if the skin is not protected with sunscreen preparations with a high protection index, may contribute to solar aging skin becoming thickened. There are wrinkles and furrows with clearly marked hyperkeratosis, i.e. thickening of the stratum corneum. In addition, there are telangiectasias and extravasations are easily formed. In such a changed skin, in places particularly exposed to the sun, pre-neoplastic conditions develop. However, the skin’s sun aging process can be slowed down. For this purpose, retinoids (vitamin A derivatives) are used, which, due to the fact that they increase the skin’s sensitivity to the sun’s rays, require the use of protective preparations with a high protection factor. Alpha-hydroxy acids (AHAs) and antioxidants are also used to prevent skin aging.
Multiform light eruptions – symptoms and treatment
Another common dermatosis caused by exposure to UV rays in childhood is multiform light rash. Erythematous, follicular and follicular lesions are located on exposed parts of the body. The time between exposure to radiation and the appearance of changes varies from 18 hours to 5 days. Sometimes the sun’s rays (UVA) passing through the glass are also harmful. Rashes appear in childhood and recur continuously in the spring. The use of beta-carotene is recommended to relieve symptoms. Skin hardening with PUVA photochemotherapy, i.e. irradiation with UVA rays after the administration of photosensitizing psoralens, is also effective. Topically recommended are sun protection measures with a high protection index (preferably 50+).
Symptoms and treatment of light urticaria
It is a rare form of urticaria caused by sunlight light urticariaIn which, a few minutes after exposure, blisters appear that last for several hours and then disappear without leaving any traces on the skin. The disease is more common in women than in men and begins at the age of 10-50. Treatment is based on very high doses of antihistamines and is not always effective. Desensitization is also used, i.e. the skin becomes accustomed to increasing doses of radiation, which leads to the development of tolerance to it. However, most sufferers must constantly avoid the sun’s rays.
Any type of rays can be sensitized, both UVB rays, which do not penetrate clothes and windows, and UVA rays, which are also visible on a cloudy day. In addition, the rays penetrate the glass, which can also be harmful to people driving the car. A much rarer type of allergy is sensitization to visible light, which can also occur due to exposure to light emitted by fluorescent lamps.
Chronic solar changes
Another group of medical conditions related to exposure to UVA / UVB radiation are chronic solar changes. There are three clinical variants that differ in severity and course.
- Persistent light reactions – these are chronic eczema lesions most often occurring in the place of sunlight, although sometimes they are located on protected parts (in a situation where the radiation penetrated through clothing). It is a chronic disease in which some patients develop a contact allergy, mainly to chromium and some plants.
- Solar eczema – This is an eczema that occurs on skin that is exposed to light and is caused by UVB rays.
- Actinic reticuloid – in some cases, most often in older men, deeper infiltrative lesions develop, of which lymphomas are extremely rare. Changes occur on parts of the body that are exposed to sunlight. The protective effect is the intake of beta-carotene from early spring to autumn, which prevents relapses. You should also use sun protection preparations with a high protection index.
– Melasma is the most common discoloration caused by the sun. Brown spots on the face are most common in young women using hormonal contraception. They can also appear as a result of the increase in the level of hormones during pregnancy.
– Most people develop phototoxic reactions under the influence of substances that increase the skin’s reaction to ultraviolet rays. Triggers can be plants, drugs, or chemicals, externally acting or administered orally (certain antihypertensive, anti-arrhythmic or anti-epileptic drugs, contraceptives, and certain herbs such as St. John’s wort). Erythema and then discoloration may also appear at the site of contact with plant phototoxic agents, e.g. in cologne, perfumes or other cosmetics.
– Photoallergic reactions are another type of photodermatosis. They can be caused by drugs used orally (so-called photoallergic reactions of the delayed hypersensitivity type) or external drugs, cosmetics, e.g. antibacterial agents added to soaps. Hypersensitivity to the sun can also manifest itself in the so-called light red inflammation of the lips. In this case, lipsticks with sunscreen are recommended.
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