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Prolonged optical exposure to sunlight, especially intense ultraviolet light, may be linked to cortical cataracts, [50] [15] and high levels of visible light is maybe linked to macular degeneration. However, significant daily exposure to bright light may be necessary for children to avoid myopia (nearsightedness). [51]
Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun.Common symptoms in humans and other animals include red or reddish skin that is hot to the touch or painful, general fatigue, and mild dizziness.
Another transcription factor NF-κB, which is also activated by UV light, also increases the expression of MMP-9. The up-regulation of MMP can occur even after minimal exposure to UV, hence, exposure to UV radiation which is inadequate to cause sunburn can thus facilitate the degradation of skin collagen and lead to presumably, eventual photoaging.
This process of absorption works to reduce the risk of DNA damage and the formation of pyrimidine dimers. UVA light makes up 95% of the UV light that reaches earth, whereas UVB light makes up only about 5%. UVB light is the form of UV light that is responsible for tanning and burning. Sunscreens work to protect from both UVA and UVB rays.
UV-B, predominantly responsible for the harmful effects of sunlight, poses the highest risk for erythema, photokeratitis, sunburn and skin cancer. [14] [15] [16] While longer UV-C wavelengths and UV-A can also cause damage, their effects are less severe than UV-B. In contrast, far-UVC has shown remarkably different results.
This can be alleviated at least to some extent by the prior application of a suitable-strength sunscreen, which also hinders the tanning process due to the blocking of UV light. Overexposure to ultraviolet radiation is known to cause skin cancer, [19] make skin age and wrinkle faster, [20] mutate DNA, [21] and impair the immune system. [22]
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Solar urticaria is an immunoglobulin E-mediated hypersensitivity that can be introduced through primary or secondary factors, or induced by exogenous photosensitization. [15] [16] Primary SU is believed to be a type I hypersensitivity (a mild to severe reaction to an antigen including anaphylaxis) in which an antigen, or substance provoking an immune response, is "induced by UV or visible ...