WHAT DOES SPF MEAN?
The first sunscreen was invented in Australia in 1932 by a chemist named Milton Blake formulated with a UV filter ‘salol (Phenyl salicylate)’ at a concentration of ‘10%.
SUN PROTECTION FACTOR
SPF was introduced in 1974 and is a measure of the amount of ultraviolet radiation that is required to cause a sunburn on sunscreen-protected skin, relative to the amount of ultraviolet radiation required to produce a sunburn on unprotected skin. SPF numbers typically refer only to UVB rays, but some sunscreens can protect against both UVA and UVB rays
For example, SPF 15 means 1/15th of UVB, or “burning” rays will reach the skin, assuming appropriate application of sunscreen at 2mg/cm2.
It is important to note that sunscreens with higher SPF do not last or remain effective on the skin any longer than lower SPF and must be continually reapplied every two hours.
SPF numbers range from 2 to 100. There is not a sunscreen on the market that can block ALL UV rays, but in general, this is what we know:
SPF 15: Blocks 93% of UVB rays
SPF 30: Blocks 97% of UVB rays
SPF 50: Blocks 98% of UVB rays
As the SPF value increases, sunburn protection increases.
There is a widespread misunderstanding that SPF relates to the time of solar exposure. For example, many consumers believe that, if they normally get sunburn in one hour, then an SPF 15 sunscreen allows them to stay in the sun 15 hours (i.e., 15 times longer) without getting burned. This is NOT TRUE. SPF is NOT directly related to time of sun exposure, but rather, to amount of sun exposure.
To make things more confusing, the inverse is actually true. The AMOUNT of solar energy IS related to solar exposure time, but there are other things that impact the AMOUNT of solar energy, including INTENSITY.
Here is an example:
The following exposures may result in the same amount of solar energy:
•one hour at 9:00 a.m.
•15 minutes at 1:00 p.m.
Are you confused yet? This is the exact reason why there are misconceptions and misunderstandings. I hope this has allowed for some clarification. When it comes to skin aging, SPF is not an accurate measure, as UVA rays cause skin cell damage without visible redness or burning.
We suggest applying sunscreen daily and reapplying often. Our Bronzee Solaire Hydratant: Hydrating Tinted Sunshield SPF 50 is perfect for daily application. This mineral-based, organic sunshield is a synergistic and powerful formulation that lends hydration, anti-aging, brightening, and broad-spectrum UV protective benefits. You will both calm and boost your skin’s moisture content, prevent photo-aging, and protect against free-radical insults all at the same time.