Every year some 16 million people in the world suffer from blindness due to a loss of transparency in the lens. WHO estimates suggest that up to 10% of cataracts may be caused by overexposure to UV radiation and are therefore avoidable.

What is extreme uvrays

Stereo microscopes, also known as dissecting microscopes, are used for viewing larger specimens in three dimensions. They have lower magnification but provide a wider field of view, making them suitable for examining objects such as insects, plants, or geological samples.

Most experiments to date have concentrated on UV-B, as it appears to be more effective than UV-A in causing immunosuppression. There are hints that UV-A and UV-B radiation is absorbed by different molecules in the skin. This leads to changes in the distribution and activity of some of the key molecular and cellular players of the immune system. An altered balance of the immune response through cells and antibodies may reduce the body's ability to defend itself against certain diseases.

Magnification refers to the ability of the microscope to make the specimen appear larger than its actual size. This is achieved by using a combination of objective lenses with different magnification powers. The total magnification is calculated by multiplying the magnification of the objective lens by the magnification of the eyepiece.

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Staining is another crucial step in sample preparation for light microscopy. Stains are used to selectively color different components of the sample, making them more visible under the microscope. Various types of stains are available, including dyes that bind to specific cellular structures or fluorescent probes that emit light when excited by specific wavelengths.

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An extreme form of photokeratitis is snow blindness. It sometimes occurs in skiers and climbers who experience extreme UV levels due to high altitude conditions and very strong ground reflection – fresh snow can reflect up to 80% of incident UV radiation. These extreme UV levels kill the outer cells of the eyeball leading to blindness. Snow blindness is very painful when the dead cells are being shed. In most cases new cells grow quickly, and vision is restored within a few days. Very severe snow blindness may involve complications such as chronic irritations or tearing.

"Sun allergy" refers to various skin conditions induced by UV radiation. The most common form of sun allergy is polymorphic light dermatosis. Following exposure to UV, in particular to UVA, the skin may develop patchy reddening, blisters, and nodules (papules) with an intense itching sensation, typically affecting the neck, upper chest, upper arms, backs of the hands, or thighs. The "Mallorca acne" is a special form of polymorphic light dermatosis whereby skin lesions are caused by the interaction of UV radiation and lipids from sunscreen (or the body’s own cutaneous sebum).

Sample preparation techniques for light microscopy involve a series of steps to ensure that the sample is properly prepared for observation under the microscope. These techniques aim to enhance the visibility and contrast of the sample, allowing for better resolution and analysis.

In recent years, there have been advancements in sample preparation techniques for light microscopy. For example, immunostaining techniques have become more sophisticated, allowing for the visualization of specific proteins or molecules within a sample. Additionally, the development of super-resolution microscopy techniques has enabled researchers to achieve higher resolution and better visualization of subcellular structures.

In recent years, advancements in technology have led to the development of more sophisticated light microscopes, such as confocal microscopes and super-resolution microscopes. These instruments offer even higher resolution and imaging capabilities, allowing scientists to study biological processes at the molecular level.

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A light microscope, also known as an optical microscope, is a scientific instrument that uses visible light and a series of lenses to magnify and observe small objects or organisms that are otherwise invisible to the naked eye. It is one of the most commonly used tools in biology and other scientific fields.

Overall, light microscopes have revolutionized the field of biology by enabling scientists to explore the intricate world of cells and microorganisms. They continue to be an indispensable tool for research and discovery in various scientific disciplines.

Sun exposure promotes skin ageing due to a combination of several factors. Photoaging of the skin can frequently be observed in sun-exposed individuals who have spent much time outdoors. Both UV-B and UV-A contribute to photoaging. It is a gradual process, which is irreversible. The skin gradually loses its elasticity. Wrinkles, sags, and bags are the common result of this loss of elasticity.

Squamous cell carcinomas also forms in the epithelial cells of the skin and is the second most common form of skin cancer. It appears as a thickened red scaly spot at body sites most often exposed to UV radiation and in which actinic keratosis forms as a precursor with sharply delimited reddening and a raw, sandpaper-like surface. As they sometimes metastasize, they are more dangerous than basal cell carcinomas. However, they also tend to be slow growing and can usually be removed surgically before they become a serious risk.

UV-A rays have longer wavelengths than UV-B rays, and thus penetrate deeper into the tissue layers of the eye and the skin. UV-A and UV-B rays also differ from each other by how strong their energy is, with UV-A rays having a lower amount of energy. UV-A and UV-B can therefore trigger different biological and health effects. The skinUV-A penetrates deep into the skin and can reach the dermis and subcutis, where connective tissue and blood vessels are affected, resulting in gradual loss of skin elasticity and premature ageing. UV-A darkens melanin pigment already present in the upper skin cells and creates a tan that appears quickly but also fades quickly. Most of UV-B is absorbed in the epidermis. UV-B stimulates the production of new melanin pigment within a few days, resulting in a tan that may last a relatively long time. UV-B also stimulates the cells to produce a thicker epidermis. Thus UV-B, together with UV-A, is responsible for the synthesis, darkening and thickening of the outer cell layers – these reactions are the body's defense against further UV damage.UV-B is the primary cause of sunburn. Sunburn is the result of overexposure and one serious factor which increases the risk of skin cancer. However, even doses of UV-B not high enough to cause sunburns may increase the likelihood of developing melanoma and non-melanoma skin cancers.Production of vitamin D is stimulated by UV-B radiation.The eyeAs for the skin, the UV-A and UV-B components of sun rays penetrate the eye to different depths. While UV-B radiation is completely absorbed by the cornea and lens, a small amount of UV-A penetrates through these and reaches the retina. It is under discussion whether this could cause retinal damage that manifests as health complications later in life. Among adults, around 1–2% of UV-A radiation is transmitted while for children, the transmittance is strongly age-dependent starting with transmittance of around 20% at birth and gradually decreases with age. Therefore, a child’s eye is more sensitive to UV radiation and requires special protection to prevent damage from UV exposure. The immune systemMost experiments to date have concentrated on UV-B, as it appears to be more effective than UV-A in causing immunosuppression. There are hints that UV-A and UV-B radiation is absorbed by different molecules in the skin. This leads to changes in the distribution and activity of some of the key molecular and cellular players of the immune system. An altered balance of the immune response through cells and antibodies may reduce the body's ability to defend itself against certain diseases.

Climatic droplet keratopathy is a spheroidal degeneration of the superficial corneal stroma that is generally confined to geographical areas with high levels of UV exposure such as the arctic or tropics. Climatic droplet keratopathy is causally associated with chronic UV-A and UV-B exposure.

Yes, you do. Compared to fair-skinned people, dark-skinned people have a much lower risk of developing melanoma or non-melanoma skin cancers, but there is still a risk. People with darker skin require more solar UV exposure to maintain adequate vitamin D levels, which may make them more susceptible to deficiency at high latitudes. But – regardless of skin colour - the risk of DNA damage, skin ageing, eye damage and harmful effects on the immune system remains and all protective measures are recommended.

Resolution, on the other hand, refers to the ability of the microscope to distinguish between two closely spaced objects as separate entities. It is determined by the wavelength of the light used and the numerical aperture of the objective lens. The numerical aperture is a measure of the lens' ability to gather light and is influenced by the refractive index of the medium between the lens and the specimen.

A light microscope is a type of microscope that uses visible light to magnify and observe small objects or organisms. It consists of a series of lenses that focus the light onto the specimen, allowing for detailed examination. The light microscope is one of the most commonly used tools in biological research and is essential for studying cells, tissues, and microorganisms.

During human evolution a number of mechanisms have evolved to protect the eye against effects of the sun's rays. The eye is recessed within the anatomy of the head and somewhat shielded by the eyebrow ridge and the eyelashes. Constriction of the pupil, closure of the eyelids and the squinting reflex minimize the penetration of the sun's rays into the eye. These mechanisms are activated by bright visible light and not by UV radiation – but on a cloudy day UV radiation exposure may still be high. Therefore, the effectiveness of these anatomical adaptations and natural defences in protecting against UV damage is limited.There are a number of acute and long-term effects of UV exposure on the eye.Photokeratitis and photoconjunctivitisPhotokeratitis is an inflammation of the cornea, while photoconjunctivitis refers to an inflammation of the conjunctiva, the membrane that lines the inside of the eyelids and eye socket. These inflammatory reactions may be compared to a sunburn of the very sensitive skin-like tissues of the eyeball and eyelids and usually appear within a few hours of exposure. Photokeratitis and photoconjunctivitis can be very painful, however, they are reversible and do not seem to result in any long-term damage to the eye or vision.An extreme form of photokeratitis is snow blindness. It sometimes occurs in skiers and climbers who experience extreme UV levels due to high altitude conditions and very strong ground reflection – fresh snow can reflect up to 80% of incident UV radiation. These extreme UV levels kill the outer cells of the eyeball leading to blindness. Snow blindness is very painful when the dead cells are being shed. In most cases new cells grow quickly, and vision is restored within a few days. Very severe snow blindness may involve complications such as chronic irritations or tearing.PterygiumThis growth of the conjunctiva on the surface of the eye is a common condition associated with excessive solar exposure. It is generally accepted that UV exposure is linked to the formation of pterygia. Pterygium may extend over the centre of the cornea and thereby reduce vision. It also tends to become inflamed. Even though it can be removed by surgery, the outgrowth tends to recur.Climatic droplet keratopathyClimatic droplet keratopathy is a spheroidal degeneration of the superficial corneal stroma that is generally confined to geographical areas with high levels of UV exposure such as the arctic or tropics. Climatic droplet keratopathy is causally associated with chronic UV-A and UV-B exposure.CataractsCataracts are the leading cause of blindness in the world. Proteins in the eye's lens unravel, tangle, and accumulate pigments which cloud the lens and eventually lead to blindness. Even though cataracts appear to different degrees in most individuals as they age, some studies strongly support UV-B as a risk factor for cortical cataract.  Cataracts can be surgically removed, and an artificial lens or other means of optical correction can restore vision.Every year some 16 million people in the world suffer from blindness due to a loss of transparency in the lens. WHO estimates suggest that up to 10% of cataracts may be caused by overexposure to UV radiation and are therefore avoidable.Cancer of the eyeCurrent scientific evidence suggests that different forms of eye cancer may be associated with UV exposure. Uveal melanoma, the most frequent cancer of the eyeball, sometimes requires surgical removal and is associated with high mortality. Evidence of an association with ultraviolet exposure is mixed. Basal cell carcinoma, accounting for approximately 90% of all eyelid malignancies, and squamous cell carcinoma are the two most common tumors of the eyelid.

Extreme UVwavelength

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Basal cell carcinomas arises from skin epithelial cells and is the most common type of skin cancer. It is most frequent on those parts of the body that are commonly exposed to the sun such as ears, face, neck, and forearms. The reported incidence has drastically increased over the past decades and continues to rise. They usually appear as a red lump or scaly area; however, no clear precursors have been identified. They grow slowly, rarely spread to other parts of the body (metastasize) but may form a deep sore if not removed surgically.

UV-A rays have longer wavelengths than UV-B rays, and thus penetrate deeper into the tissue layers of the eye and the skin. UV-A and UV-B rays also differ from each other by how strong their energy is, with UV-A rays having a lower amount of energy. UV-A and UV-B can therefore trigger different biological and health effects.

In summary, magnification and resolution are key parameters in light microscopy. While magnification allows for larger images of the specimen, resolution determines the level of detail that can be observed. Ongoing advancements in microscopy techniques continue to enhance the capabilities of light microscopy, enabling scientists to explore the microscopic world with greater precision and clarity.

One of the main effects of UV radiation is its ability to suppress the body’s immunological response to antigens. UV exposure triggers a series of reactions in the skin that may lead to local, but possibly also systemic immunosuppression. These reactions are a complicated interaction involving a wide range of different cell types such as skin cells and cells of the immune system. The precise mechanisms are yet to be fully understood. An example of UV induced immunosuppression is the recurrent eruption of cold sores when the immune system can no longer keep the virus herpes simplex under control

Melanoma is the least common but the most dangerous type of skin cancer, accounting for most skin cancer deaths. It is caused by a malignancy of melanocytes and may arise as a new mole or as changes in colour, shape, size, or sensation of an old spot, freckle, or mole. Melanomas tend to have an irregular outline and a patchy colouring. Itching is another common symptom but is also found in normal moles. If recognized and treated early, the chances of survival are good. If untreated, the tumour can develop rapidly, and cancer cells can spread to other parts of the body. Melanoma may occur early in life, and its incidence is rapidly increasing worldwide. There is strong evidence that melanoma occurs due to intermittent UV exposure (occasional exposure to short periods of intense sunlight) and severe sunburns during childhood and adolescence.

In recent years, advancements in technology have led to the development of more sophisticated light microscopes, such as confocal microscopes and fluorescence microscopes. These instruments utilize advanced optical techniques and components to enhance the resolution and contrast of the images obtained. Additionally, digital imaging and computer software have allowed for the capture, analysis, and storage of microscope images, enabling further research and analysis.

The optical principles of a light microscope involve the interaction of light with the specimen being observed. When light passes through the specimen, it undergoes refraction, which causes the light rays to bend. This bending of light allows the microscope to magnify the image of the specimen. The lenses in the microscope, including the objective lens and the eyepiece, work together to focus and magnify the image.

A set of substances that can be found in medications, herbal remedies and cosmetics like fragrances and soaps may provoke phototoxic reactions of the skin. These substances are said to have a photosensitizing effect. A minimal dose of UV radiation is sufficient to trigger an allergic reaction leading to rash or severe sunburn. Photosensitizing substances can also be found in certain plants and foods, such as citrus fruits, celery, or giant hogweed. If these plants are eaten or touched, subsequent exposure to UV radiation can lead to skin diseases.

UV-B is the primary cause of sunburn. Sunburn is the result of overexposure and one serious factor which increases the risk of skin cancer. However, even doses of UV-B not high enough to cause sunburns may increase the likelihood of developing melanoma and non-melanoma skin cancers.

UV-A penetrates deep into the skin and can reach the dermis and subcutis, where connective tissue and blood vessels are affected, resulting in gradual loss of skin elasticity and premature ageing. UV-A darkens melanin pigment already present in the upper skin cells and creates a tan that appears quickly but also fades quickly.

Sunburn is an inflammation of the skin largely triggered by UV-B. This inflammation manifests as reddening and swelling of the affected areas of skin, as well as blistering in particularly serious cases. The resulting discomfort reaches its peak within 12 to 36 hours. Frequent sunburns during childhood and adolescence seriously increase the risk of developing skin cancer (melanoma). The occurrence of erythema remains the dermatological indicator for overexposure of the skin to UV radiation. However, DNA damage relevant to skin cancer can occur even before the erythema threshold is reached.

Photokeratitis is an inflammation of the cornea, while photoconjunctivitis refers to an inflammation of the conjunctiva, the membrane that lines the inside of the eyelids and eye socket. These inflammatory reactions may be compared to a sunburn of the very sensitive skin-like tissues of the eyeball and eyelids and usually appear within a few hours of exposure. Photokeratitis and photoconjunctivitis can be very painful, however, they are reversible and do not seem to result in any long-term damage to the eye or vision.

The only beneficial effect of UV, triggered by UV-B, is the stimulation of the production of vitamin D. Vitamin D has an important function in increasing calcium and phosphorus absorption from food and plays a crucial role in skeletal development, immune function, and blood cell formation. Thus, this beneficial effect from UV exposure must be weighed against the simultaneous adverse health effects to the eyes and skin.

Overall, sample preparation techniques for light microscopy play a crucial role in obtaining clear and detailed images of samples. These techniques continue to evolve, driven by advancements in technology and the need for more precise and accurate analysis in various scientific disciplines.

A light microscope is a type of microscope that uses visible light to magnify and observe small objects or samples. It is a widely used tool in various scientific fields, including biology, medicine, and materials science. The light microscope definition refers to the use of lenses and light sources to produce magnified images of samples.

Cataracts are the leading cause of blindness in the world. Proteins in the eye's lens unravel, tangle, and accumulate pigments which cloud the lens and eventually lead to blindness. Even though cataracts appear to different degrees in most individuals as they age, some studies strongly support UV-B as a risk factor for cortical cataract.  Cataracts can be surgically removed, and an artificial lens or other means of optical correction can restore vision.

Overall, the light microscope remains an essential tool in scientific research, allowing scientists to explore the intricate details of the microscopic world and gain a deeper understanding of biological processes and structures.

Phase contrast microscopes are designed to enhance the contrast of transparent specimens, such as living cells, by converting differences in refractive index into variations in brightness. This technique allows for the visualization of cellular structures that would otherwise be difficult to observe.

This growth of the conjunctiva on the surface of the eye is a common condition associated with excessive solar exposure. It is generally accepted that UV exposure is linked to the formation of pterygia. Pterygium may extend over the centre of the cornea and thereby reduce vision. It also tends to become inflamed. Even though it can be removed by surgery, the outgrowth tends to recur.

The components of a light microscope typically include an illuminator, which provides a light source, a condenser, which focuses the light onto the specimen, an objective lens, which magnifies the image, and an eyepiece, which further magnifies the image for the observer. The microscope also has a stage where the specimen is placed and a focus adjustment mechanism to bring the specimen into sharp focus.

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SunSmart Global UV App Free application for mobile devices that describes the level of solar UV radiation at a specific location. It also provides time slots when to apply sun protection measures, in an effort to reduce the global burden of skin cancer and UV-related eye damage. Download SunSmart Global UV App

A light microscope, also known as an optical microscope, is a scientific instrument that uses visible light and a system of lenses to magnify and observe small objects or specimens. It is one of the most commonly used types of microscopes in various fields of science, including biology, medicine, and materials science. The basic principle of a light microscope involves passing light through the specimen, which interacts with the sample and produces an image that can be viewed through the eyepiece or captured using a camera. The lenses in the microscope system help to magnify the image, allowing for detailed examination of the specimen's structure and morphology. Light microscopes can have different configurations, such as compound microscopes with multiple lenses or stereo microscopes for three-dimensional observation. They have played a crucial role in advancing scientific knowledge and understanding of the microscopic world.

Most of UV-B is absorbed in the epidermis. UV-B stimulates the production of new melanin pigment within a few days, resulting in a tan that may last a relatively long time. UV-B also stimulates the cells to produce a thicker epidermis. Thus UV-B, together with UV-A, is responsible for the synthesis, darkening and thickening of the outer cell layers – these reactions are the body's defense against further UV damage.

Vitamin D deficiency is possible for those who have very limited sun exposure, such as the elderly who are housebound or with age-related reduced vitamin D synthesis, those with dark pigmented skin who live in high-latitude countries where UV levels are relatively low, traditionally veiled persons, and people whose vitamin D metabolism does not function properly. Vitamin D deficiency should only be medically diagnosed and treated. Vitamin D supplementation or medication should be carried out under medical supervision. Recognizing the need for vitamin D, many countries have introduced supplements into common food like flour, cereals, and milk. Naturally occurring vitamin D is very rare in the human diet and is mainly present in fatty fish and cod liver oil. Most oral multivitamin tablets also contain adequate daily dose of vitamin D.

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During human evolution a number of mechanisms have evolved to protect the eye against effects of the sun's rays. The eye is recessed within the anatomy of the head and somewhat shielded by the eyebrow ridge and the eyelashes. Constriction of the pupil, closure of the eyelids and the squinting reflex minimize the penetration of the sun's rays into the eye. These mechanisms are activated by bright visible light and not by UV radiation – but on a cloudy day UV radiation exposure may still be high. Therefore, the effectiveness of these anatomical adaptations and natural defences in protecting against UV damage is limited.

The only beneficial effect of UV, triggered by UV-B, is the stimulation of the production of vitamin D. Vitamin D has an important function in increasing calcium and phosphorus absorption from food and plays a crucial role in skeletal development, immune function, and blood cell formation. Thus, this beneficial effect from UV exposure must be weighed against the simultaneous adverse health effects to the eyes and skin. Based on current scientific knowledge, sufficient vitamin D synthesis is achieved by healthy people when exposing the face, hands, and arms uncovered and without sunscreen two to three times a week to half the time it would usually take unprotected skin to develop a sunburn (corresponding to around 12 minutes for sensitive people (skin type II)) with a UV index of 7.Vitamin D deficiency is possible for those who have very limited sun exposure, such as the elderly who are housebound or with age-related reduced vitamin D synthesis, those with dark pigmented skin who live in high-latitude countries where UV levels are relatively low, traditionally veiled persons, and people whose vitamin D metabolism does not function properly. Vitamin D deficiency should only be medically diagnosed and treated. Vitamin D supplementation or medication should be carried out under medical supervision. Recognizing the need for vitamin D, many countries have introduced supplements into common food like flour, cereals, and milk. Naturally occurring vitamin D is very rare in the human diet and is mainly present in fatty fish and cod liver oil. Most oral multivitamin tablets also contain adequate daily dose of vitamin D.

The first step in sample preparation is fixation, which involves preserving the sample's structure and preventing decay or degradation. This is typically done by using chemical fixatives such as formaldehyde or glutaraldehyde. After fixation, the sample may undergo dehydration, embedding, and sectioning processes, depending on the nature of the sample and the desired analysis.

There is no such thing as a healthy tan! The skin produces a dark-coloured pigment, melanin, as a shield against further damage from UV radiation. The darkening provides some protection against sunburn. With a UV-A- and UV-B-induced tan a sun protection factor of between 2 and 4 can be achieved. However, it is no defence against long-term UV damage such as skin cancer. A suntan may be cosmetically desirable, but in fact it is a sign that your skin has been damaged and has attempted to protect itself.

Free application for mobile devices that describes the level of solar UV radiation at a specific location. It also provides time slots when to apply sun protection measures, in an effort to reduce the global burden of skin cancer and UV-related eye damage.

There are several types of light microscopes, including compound, stereo, and phase contrast microscopes. Compound microscopes are the most widely used and have two sets of lenses - the objective lens and the eyepiece. They provide high magnification and resolution, allowing for the observation of fine details in cells and tissues.

A light microscope is a type of microscope that uses visible light to magnify and resolve the details of a specimen. It consists of a series of lenses that work together to enlarge the image of the specimen, allowing scientists to observe and study its structure and characteristics.

As for the skin, the UV-A and UV-B components of sun rays penetrate the eye to different depths. While UV-B radiation is completely absorbed by the cornea and lens, a small amount of UV-A penetrates through these and reaches the retina. It is under discussion whether this could cause retinal damage that manifests as health complications later in life. Among adults, around 1–2% of UV-A radiation is transmitted while for children, the transmittance is strongly age-dependent starting with transmittance of around 20% at birth and gradually decreases with age. Therefore, a child’s eye is more sensitive to UV radiation and requires special protection to prevent damage from UV exposure.

UV radiation can cause short- and long-term health effects on the skin. In addition to the well-known short-term effects such as sunburn or allergic reactions, long-term effects like skin cancer represent a chronic health risk. Skin cancer risk is strongly correlated with the duration and frequency of sun exposure over one’s lifetime. Cumulative UV dose is related to the development of squamous cell carcinoma while intermittent intense UV exposure and sunburn are related to melanoma.

Yes, you do. Compared to fair-skinned people, dark-skinned people have a much lower risk of developing melanoma or non-melanoma skin cancers, but there is still a risk. People with darker skin require more solar UV exposure to maintain adequate vitamin D levels, which may make them more susceptible to deficiency at high latitudes. But – regardless of skin colour - the risk of DNA damage, skin ageing, eye damage and harmful effects on the immune system remains and all protective measures are recommended.

One of the main effects of UV radiation is its ability to suppress the body’s immunological response to antigens. UV exposure triggers a series of reactions in the skin that may lead to local, but possibly also systemic immunosuppression. These reactions are a complicated interaction involving a wide range of different cell types such as skin cells and cells of the immune system. The precise mechanisms are yet to be fully understood. An example of UV induced immunosuppression is the recurrent eruption of cold sores when the immune system can no longer keep the virus herpes simplex under control

In light microscopy, the maximum resolution is limited by the diffraction of light waves. According to the Abbe diffraction limit, the resolution is approximately half the wavelength of the light used. However, recent advancements in microscopy techniques, such as super-resolution microscopy, have pushed the limits of resolution beyond the diffraction limit. These techniques utilize fluorescent dyes and complex imaging algorithms to achieve resolutions at the nanometer scale, allowing scientists to observe cellular structures and processes in unprecedented detail.

UV radiation is the main cause of skin cancers, the most frequent cancers in fair-skinned populations. Risk factors for skin cancer include skin type, large congenital or clinically atypical moles, the number of moles, a family history of skin cancer, also acquired risk factors like immunosuppression-inducing diseases, and the UV exposure pattern the individual lifetime UV exposure (lifetime dose), intermittent UV exposures and sunburns.

UV radiation can cause short- and long-term health effects on the skin. In addition to the well-known short-term effects such as sunburn or allergic reactions, long-term effects like skin cancer represent a chronic health risk. Skin cancer risk is strongly correlated with the duration and frequency of sun exposure over one’s lifetime. Cumulative UV dose is related to the development of squamous cell carcinoma while intermittent intense UV exposure and sunburn are related to melanoma.SuntanThere is no such thing as a healthy tan! The skin produces a dark-coloured pigment, melanin, as a shield against further damage from UV radiation. The darkening provides some protection against sunburn. With a UV-A- and UV-B-induced tan a sun protection factor of between 2 and 4 can be achieved. However, it is no defence against long-term UV damage such as skin cancer. A suntan may be cosmetically desirable, but in fact it is a sign that your skin has been damaged and has attempted to protect itself.SunburnSunburn is an inflammation of the skin largely triggered by UV-B. This inflammation manifests as reddening and swelling of the affected areas of skin, as well as blistering in particularly serious cases. The resulting discomfort reaches its peak within 12 to 36 hours. Frequent sunburns during childhood and adolescence seriously increase the risk of developing skin cancer (melanoma). The occurrence of erythema remains the dermatological indicator for overexposure of the skin to UV radiation. However, DNA damage relevant to skin cancer can occur even before the erythema threshold is reached. Sun allergy"Sun allergy" refers to various skin conditions induced by UV radiation. The most common form of sun allergy is polymorphic light dermatosis. Following exposure to UV, in particular to UVA, the skin may develop patchy reddening, blisters, and nodules (papules) with an intense itching sensation, typically affecting the neck, upper chest, upper arms, backs of the hands, or thighs. The "Mallorca acne" is a special form of polymorphic light dermatosis whereby skin lesions are caused by the interaction of UV radiation and lipids from sunscreen (or the body’s own cutaneous sebum).Phototoxic reactionsA set of substances that can be found in medications, herbal remedies and cosmetics like fragrances and soaps may provoke phototoxic reactions of the skin. These substances are said to have a photosensitizing effect. A minimal dose of UV radiation is sufficient to trigger an allergic reaction leading to rash or severe sunburn. Photosensitizing substances can also be found in certain plants and foods, such as citrus fruits, celery, or giant hogweed. If these plants are eaten or touched, subsequent exposure to UV radiation can lead to skin diseases.Premature skin ageing - the wrinkle factorSun exposure promotes skin ageing due to a combination of several factors. Photoaging of the skin can frequently be observed in sun-exposed individuals who have spent much time outdoors. Both UV-B and UV-A contribute to photoaging. It is a gradual process, which is irreversible. The skin gradually loses its elasticity. Wrinkles, sags, and bags are the common result of this loss of elasticity.Skin CancerUV radiation is the main cause of skin cancers, the most frequent cancers in fair-skinned populations. Risk factors for skin cancer include skin type, large congenital or clinically atypical moles, the number of moles, a family history of skin cancer, also acquired risk factors like immunosuppression-inducing diseases, and the UV exposure pattern the individual lifetime UV exposure (lifetime dose), intermittent UV exposures and sunburns.The major types of skin cancer are listed below in order of increasing severity and decreasing frequency. Basal cell carcinomaBasal cell carcinomas arises from skin epithelial cells and is the most common type of skin cancer. It is most frequent on those parts of the body that are commonly exposed to the sun such as ears, face, neck, and forearms. The reported incidence has drastically increased over the past decades and continues to rise. They usually appear as a red lump or scaly area; however, no clear precursors have been identified. They grow slowly, rarely spread to other parts of the body (metastasize) but may form a deep sore if not removed surgically.Squamous cell carcinomasSquamous cell carcinomas also forms in the epithelial cells of the skin and is the second most common form of skin cancer. It appears as a thickened red scaly spot at body sites most often exposed to UV radiation and in which actinic keratosis forms as a precursor with sharply delimited reddening and a raw, sandpaper-like surface. As they sometimes metastasize, they are more dangerous than basal cell carcinomas. However, they also tend to be slow growing and can usually be removed surgically before they become a serious risk.Melanoma skin cancersMelanoma is the least common but the most dangerous type of skin cancer, accounting for most skin cancer deaths. It is caused by a malignancy of melanocytes and may arise as a new mole or as changes in colour, shape, size, or sensation of an old spot, freckle, or mole. Melanomas tend to have an irregular outline and a patchy colouring. Itching is another common symptom but is also found in normal moles. If recognized and treated early, the chances of survival are good. If untreated, the tumour can develop rapidly, and cancer cells can spread to other parts of the body. Melanoma may occur early in life, and its incidence is rapidly increasing worldwide. There is strong evidence that melanoma occurs due to intermittent UV exposure (occasional exposure to short periods of intense sunlight) and severe sunburns during childhood and adolescence.

Based on current scientific knowledge, sufficient vitamin D synthesis is achieved by healthy people when exposing the face, hands, and arms uncovered and without sunscreen two to three times a week to half the time it would usually take unprotected skin to develop a sunburn (corresponding to around 12 minutes for sensitive people (skin type II)) with a UV index of 7.

Current scientific evidence suggests that different forms of eye cancer may be associated with UV exposure. Uveal melanoma, the most frequent cancer of the eyeball, sometimes requires surgical removal and is associated with high mortality. Evidence of an association with ultraviolet exposure is mixed. Basal cell carcinoma, accounting for approximately 90% of all eyelid malignancies, and squamous cell carcinoma are the two most common tumors of the eyelid.