The sunlight has a profound effect on our skin, and this can result in premature aging, skin cancer and a host of other skin-related conditions. Exposure to ultraviolet (UV) rays accounts for about 90% of all skin lesion symptoms, especially premature aging!
Os The Facts About UV Radiation
The sun emits UV radiation that we divide into categories based on their relative wavelength (measured by a nanometer or nm):
- UVC radiation (100 to 290 nm)
- UVB radiation (290 to 320 nm)
- UVA radiation (320 at 400 nm)
UVC radiation has the shortest wavelength and is almost completely absorbed by the ozone layer. As such, it does not really affect the skin. However, UVC radiation can be found in artificial sources such as mercury arc lamps and germicidal lamps.UVB radiation affects the most external skin’s layer (epidermis) and is the main cause of sunburn. It is more intense between 10 o’clock in the morning and 2 o’clock in the afternoon when the sunlight is stronger. It is also more intense during the summer months, accounting for about 70% of a person’s annual UVB exposure. Because of the wavelength, UVB does not easily penetrate the glass.UVA radiation, by contrast, is the one that has a bigger effect on the skin. Studies have shown that UVA is a major contributor to skin damage. It penetrates deeper into the skin and with greater intensity than the UVB. And, unlike UVB, UVA is not filtered by glass.
Harmful effects of UVA and UVB
Both UVA and UVB radiation can cause a number of skin-related abnormalities, including wrinkles, age-related disorders, skin cancer, and decreased immunity to infection. Although we do not fully understand the mechanisms for these changes, some believe that collagen breakdown and free radical formation can interfere with DNA repair at the molecular level!UV radiation is known to increase the number of spots on the skin in parts of the body exposed to the sun. Overexposure to the sun can also lead to the development of skin lesions called pre-cancerous actinic keratoses. They are characterized by yellow, brownish, dark spots or scales. Actinic keratoses are considered precancerous because one in 100 becomes squamous cell carcinoma. Actinic keratoses are easier to feel than see and usually appear on the face, ears, and back of the hands. Exposure to UV rays can also cause seborrheic keratoses, which appear as wart-like lesions on the skin. Unlike actinic keratoses, seborrheic keratoses do not become cancerous.
Collagen Collapses and Free Radicals
UV radiation can cause collagen deterioration at a rate higher than normal aging. It does this by penetrating the middle layer of the skin (dermis), causing the abnormal accumulation of elastin. When these elastins accumulate, enzymes are produced that inadvertently break collagen and create the so-called “sunspots”.
Prolonged exposure only speeds up the process, leading to more wrinkling and sagging!
UV radiation is also one of the main creators of free radicals. Free radicals are unstable oxygen molecules that have only one electron instead of two. Because electrons are found in pairs, the molecule needs to eliminate the lost electron from other molecules, causing a chain reaction that can damage cells at the molecular level. Free radicals not only increase the number of enzymes that break down collagen but can also alter the genetic material of a cell in a way that can lead to cancer.
Changes in the skin caused by the sun
Exposure to UV rays causes skin irregular thickening and thinning, called solar elastosis, resulting in coarse wrinkles and yellowish discoloration. It can also make the walls of blood vessels thinner, leading to the formation of bruises and veins (telangiectasias) on the face. By far the most common pigment changes induced by the sun are freckles (solar lentigo). A freckle is caused when the pigment-producing cells of the skin (melanocytes) are damaged, increasing the aged appearance. Larger freckles, also known as age spots, usually appear on the backs of the hands, chest, shoulders, upper arms and upper back. While age spots are often seen in older adults, they are not related to age, as its name suggests, but a consequence of sun injury, triggering premature aging.
Exposure to UV rays can also lead to white spots on the legs, hands, and arms as melanocytes are progressively destroyed by solar radiation!
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