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However, excessive exposure to ultraviolet radiation, especially at undesirable wavelengths, can cause direct DNA damage, sunburn, and increase the risk of skin cancer. [6] In contrast to low-dose UV-B exposure, UV-A light increases the risk of skin cancer because it penetrates deeper into the epidermis and is typically administered at much ...
Ultraviolet rays are usually invisible to most humans. ... The amount of sunscreen that penetrates into the lower layers of the skin may be large enough to cause damage.
Typically, it can provide a modest Sun Protection Factor (SPF) of 3, meaning that tanned skin would tolerate up to 3 times the UV exposure as pale skin. [12] However, in order to cause true melanogenesis-tanning by means of UV exposure, some direct DNA photodamage must first be produced, and this requires UVB exposure (as present in natural ...
[17] [18] [19] UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D. [20] Time of day, time of year, geographic latitude, ground altitude, cloud cover, smog, skin melanin content, and sunscreen are among the factors that greatly affect UV intensity and vitamin D synthesis, [19 ...
Light therapy for skin conditions like psoriasis usually use 313 nanometer UVB though it may use UVA (315–400 nm wavelength) or a broader spectrum UVB (280–315 nm wavelength). UVA combined with psoralen, a drug taken orally, is known as PUVA treatment. In UVB phototherapy the exposure time is very short, seconds to minutes depending on ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 22 January 2025. "Skin pigmentation" redirects here. For animal skin pigmentation, see Biological pigment. Extended Coloured family from South Africa showing some spectrum of human skin coloration Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among ...
"Many systems also include a small amount of infrared light — which is not visible on the spectrum of light — and penetrates the skin more deeply," says Stevenson. Near-infrared light has ...
UVB-induced apoptosis is the programmed cell death of cells that become damaged by ultraviolet rays. This is notable in skin cells, to prevent melanoma . Some studies have shown that exercise accelerates this process.