Protecting the Skin from Sunlight Exposure
1. Info about using SPF sunscreen products to protect against ultraviolet light (UV light)
A person’s skin should be protected with sunscreen products with high SPF to protect against UV light.
According to studies, people usually apply a thinner up to mid-high amount of SPF sunscreen. In these application amounts, the actual effective SPF is much lower than the product rating SPF.
A thinner application of SPF sunscreen is typically about 0.25 of the SPF product rating. For example, SPF 60 sunscreen provides UV protection of about SPF 15 when applied in thinner application.
A mid-high application of SPF sunscreen is typically about 0.5 of the product SPF rating. For example, a mid-high application of SPF 60 product provides UV protection of about SPF 30.
The vast majority of sunscreen users apply the SPF product to the skin between thinner and mid-high thickness. To get the full SPF rating would require applying more SPF product than people feel comfortable or normal to apply on the skin.
When using sunscreen, it is best to buy a product with high SPF and apply it in mid-high thickness. Users should understand and expect that the actual effective SPF is substantially lower. A rough estimate is that the actual effective SPF is about 50% of the product rating SPF.
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2. Info about reducing skin freckling from sunlight (UV light and bright visible light)
From intuitive guidance, freckling of skin is caused both by UV light as well as visible light from the sun.
Reducing both UV light and visible light transmitted to the skin is helpful for reducing skin freckling caused by sunlight exposure.
For light-colored skin, freckling from sunlight exposure is caused 70% by UV light in sunlight and 30% by visible light in sunlight.
For mid-dark skin, freckling from sunlight exposure is caused 80% by UV light in sunlight and 20% by visible light in sunlight.
It is recommended to use both high SPF sunscreen plus opaque full coverage foundation make-up in order to reduce skin freckling from exposure to sunlight.
This can be applied as two separate skin care products, or it can be applied using an opaque full coverage foundation product that includes high SPF sunscreen. Some SPF sunscreen products are made to be more compatible with doing a follow-up process of applying make-up such as opaque full coverage foundation.
SPF sunscreen by itself is not protection against exposure to visible light.
Using opaque full coverage foundation without also applying make-up powder can provide about a factor of 5x reduction in the visible light that is transmitted to the skin.
Using opaque full coverage foundation plus applying make-up powder can provide about a factor of 6.5x reduction in the visible light that is transmitted to the skin.
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