The use of sunscreen has been shown to decrease the formation of actinic keratocytes, which are linked to squamous cell carcinoma. Animal models have shown that sunscreens reduce the incidence of basal and squamous tumor cells, which are related to UVB, but there are some studies that suggest that the use of filters Solar is associated with an increased risk of melanoma. This may reflect an inadequate application of sunscreen, lack of durability of the application, the lack or inadequacy of UVA filters in sunscreen preparations combined this with a long bath of sunlight, the photo instability causes a reduced sunscreens protection, or production of reactive free radicals or mutagens into the cream. A link between the use of sunscreens and melanoma, however, is still to be debated and it is not clear. The SPF of sunscreens is an internationally accepted standard which establishes the effectiveness of sunscreen: is based solely on the prevention of erythema (sunburn), which is mainly induced by UVB and erythema is the criterion by which people limit their sun exposure. While the FPS may indicate protection against UVB-induced carcinogenesis, this can not be used as an indicator of indirect damage caused by UVA exposure, such as erythema is predominantly a response to UVB. As skin carcinogenesis is highly complex, using a range of markers for skin damage by itself is very necessary to supplement the FPS (an indicator of UVB protection) for use in the evaluation of a total cancer risk skin.
Other studies have been published that assess the direct damage of DNA, the formation of p53 and protection against UV-induced immunosuppression. There are some methods to measure the protection provided by sunscreens against UVA damage to skin, but these methods are not validated. Protection against UVA-induced free radicals, to date, has not been measured. In this study, we have adapted an electronic resonance (ESR) to measure the production of free radicals induced by UV in human skin, and evaluated the protection against free radical production provided by sunscreens. Free radicals formed by UV irradiation of the skin (which are associated with damage to DNA and protein), are usually not directly detectable at room temperature. An exception to this, however is the ascorbate radical, which is formed when ascorbate (vitamin C, an antioxidant cell) reacts with free radicals. The ascorbate radical is easily detected using spectroscopy (ESR) in biopsies of skin exposed to UV radiation and is accepted as a reliable marker for cellular free radical production and oxidative stress. We used the relative quantification of this radical in the same skin sample before and after application of sunscreens to achieve estimate the level of protection against UVA radiation offered by three popular sunscreens that claim to have UV protection on a range of densities applied.
RESULTS: Validation of the method. – The skin was irradiated with UV spectrum (ESR) recognition of ascorbate radical, which was either undetectable or detectable at very low levels in non-irradiated skin. In contrast to previous reports the ascorbate radical was not detected in the skin consist of non-irradiated in our experiments. This may be because the skin in our experiments was fully protected from light in the room, previously believed to have a small effect on the radical signal, or may have reflected in our experiments using samples of fresh skin Instead of frozen samples. The radicals formed in the sunscreen only n in vitro study