Getting a Sun tan?
Posted: Wed Mar 28, 2012 6:53 am
Does everyone know this? Controversy over sunscreen
The statement sunburn causes skin cancer is accurate when it refers to either basal-cell carcinoma, the mildest form of cancer, or squamous cell carcinoma. But the statement is false when it comes to malignant melanoma. The statistical correlation between sunburn and melanoma is due to a common cause — UV radiation. However, they are generated via two different mechanisms: Direct DNA damage is ascribed by many medical doctors to a change in behaviour of the sunscreen user due to a false sense of security afforded by the sunscreen. Other researchers blame insufficient correction for confounding factors; light-skinned individuals versus indirect DNA damage.
Topically applied sunscreen blocks UV rays as long as it does not penetrate into the skin. This prevents sunburn, suntanning, and skin cancer. If the sunscreen filter is absorbed into the skin, it prevents sunburn, but increases the amount of free radicals, which in turn increases the risk for malignant melanoma. The harmful effect of photo-excited sunscreen filters on living tissue has been shown in many photo-biological studies. Whether sunscreen prevents or promotes the development of melanoma depends on the relative importance of the protective effect from the topical sunscreen versus the harmful effects of the absorbed sunscreen. Sunburn - Wikipedia, the free encyclopedia
As a defense against UV radiation, the amount of the brown pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, blocking the UV from damaging skin tissue. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. UVB on the other hand yields a tan that takes roughly two days to develop because it stimulates the body to produce more melanin. The photochemical properties of melanin make it an excellent photoprotectant.
Sunscreen chemicals on the other hand cannot dissipate the energy of the excited state as efficiently as melanin and therefore the penetration of sunscreen ingredients into the lower layers of the skin increases the amount of free radicals and reactive oxygen species (ROS).
Some sunscreen lotions now include compounds such as titanium dioxide and zinc oxide, inert fillers which helps protect against UV rays via light scattering and physically blocking the light pathway into the dermal layers. Other UVA blocking compounds found in sunscreen include Avobenzone. There are also naturally occurring compounds found in rainforest plants that have been known to protect the skin from UV radiation damage, such as the fern Phlebodium aureum.
Some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells. The amount of sunscreen that penetrates through the stratum corneum may or may not be large enough to cause damage. In one study of sunscreens, the authors write:
The question whether UV filters acts on or in the skin has so far not been fully answered. Despite the fact that an answer would be a key to improve formulations of sun protection products, many publications carefully avoid addressing this question.
In an experiment by Hanson et al. that was published in 2006, the amount of harmful reactive oxygen species was measured in untreated and in sunscreen-treated skin. In the first 20 minutes the film of sunscreen had a protective effect and the number of ROS species was smaller. After 60 minutes, however, the amount of absorbed sunscreen was so high that the amount of ROS was higher in the sunscreen-treated skin than in the untreated skin. Sunscreen - Wikipedia, the free encyclopedia
It seems everything isn't as black and white as many may think
The statement sunburn causes skin cancer is accurate when it refers to either basal-cell carcinoma, the mildest form of cancer, or squamous cell carcinoma. But the statement is false when it comes to malignant melanoma. The statistical correlation between sunburn and melanoma is due to a common cause — UV radiation. However, they are generated via two different mechanisms: Direct DNA damage is ascribed by many medical doctors to a change in behaviour of the sunscreen user due to a false sense of security afforded by the sunscreen. Other researchers blame insufficient correction for confounding factors; light-skinned individuals versus indirect DNA damage.
Topically applied sunscreen blocks UV rays as long as it does not penetrate into the skin. This prevents sunburn, suntanning, and skin cancer. If the sunscreen filter is absorbed into the skin, it prevents sunburn, but increases the amount of free radicals, which in turn increases the risk for malignant melanoma. The harmful effect of photo-excited sunscreen filters on living tissue has been shown in many photo-biological studies. Whether sunscreen prevents or promotes the development of melanoma depends on the relative importance of the protective effect from the topical sunscreen versus the harmful effects of the absorbed sunscreen. Sunburn - Wikipedia, the free encyclopedia
As a defense against UV radiation, the amount of the brown pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, blocking the UV from damaging skin tissue. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. UVB on the other hand yields a tan that takes roughly two days to develop because it stimulates the body to produce more melanin. The photochemical properties of melanin make it an excellent photoprotectant.
Sunscreen chemicals on the other hand cannot dissipate the energy of the excited state as efficiently as melanin and therefore the penetration of sunscreen ingredients into the lower layers of the skin increases the amount of free radicals and reactive oxygen species (ROS).
Some sunscreen lotions now include compounds such as titanium dioxide and zinc oxide, inert fillers which helps protect against UV rays via light scattering and physically blocking the light pathway into the dermal layers. Other UVA blocking compounds found in sunscreen include Avobenzone. There are also naturally occurring compounds found in rainforest plants that have been known to protect the skin from UV radiation damage, such as the fern Phlebodium aureum.
Some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells. The amount of sunscreen that penetrates through the stratum corneum may or may not be large enough to cause damage. In one study of sunscreens, the authors write:
The question whether UV filters acts on or in the skin has so far not been fully answered. Despite the fact that an answer would be a key to improve formulations of sun protection products, many publications carefully avoid addressing this question.
In an experiment by Hanson et al. that was published in 2006, the amount of harmful reactive oxygen species was measured in untreated and in sunscreen-treated skin. In the first 20 minutes the film of sunscreen had a protective effect and the number of ROS species was smaller. After 60 minutes, however, the amount of absorbed sunscreen was so high that the amount of ROS was higher in the sunscreen-treated skin than in the untreated skin. Sunscreen - Wikipedia, the free encyclopedia
It seems everything isn't as black and white as many may think