I have noticed this increase of highest-ever SPF products as well!
The short answer: Sunscreen protection increases with higher SPF, but not significantly:
SPF 30 blocks 96.7% of UVB rays
SPF 50 blocks 98.0% of UVB rays
SPF 100 blocks 99.0% of UVB rays
You would assume that SPF 100 would "double" the benefits that SPF 50 provides, but the protection increase is minuscule. The products can claim that there is an increase in protection, which is true, but as you can see, it is only by 1%, and as you get higher numbers, there isn't really a significant difference (except in price!).
The long answer: Q: How does SPF work?
A: The percentage you see above is based on the formula:
Time needed for a person to burn unprotected vs. time needed for person to burn wearing sunscreen. A person who burns after 30 minutes of unprotected sun exposure is protected 30x more if they had used SPF 30.
Q: How much sunscreen should I use each outing?
A: A full ounce (shot glass full!). Most people use only a half ounce and skimp out on applying the sunscreen. Do you have an almost-full bottle of sunscreen leftover from last summer? If so, you are not using enough at each outing! The sunscreen bottle/tube should last only a few applications, if you are applying it liberally enough. Dermatologists even say that consumers should worry more about applying enough sunscreen instead of how high the SPF is.
A study published in April 2007 in the British Journal of Dermatology found that sunscreen application quantity is an important factor in application, as it is assumed by consumers that if use SPF 100, at least we would be protected with SPF 50, right? What they found: inadequate quantity of application resulted in the protection decreasing to the square root of the SPF. For example, if you use only a half ounce of SPF 100 (vs. recommended full ounce), it does not mean that you have enough coverage of SPF 50, but that you get the protection of only SPF 10 !!
I think this is worth repeating!
According to the British Journal of Dermatology study above:
- Apply ONE OUNCE (shot glass full) of SPF 100 = SPF 100 protection
- Apply only a HALF ounce of SPF = only SPF 10 protection
Q:How often should I re-apply sunscreen?
A: Every 2 hours is ideal, and more often if sweating or in water.
The Environmental Working Group (EWG), 2008, reviewed 1,000 sunscreens, and said that there is a false sense of security with high SPF, because users think they can stay out all day and not re-apply; that they are safe.
Bottom line:
- Make sure your sunscreen protects from both UVB and UVA (some of the higher SPF does not protect adequately from UVA.
- Apply sunscreen liberally: a full shot glass/ounce
- Re-apply every 2 hours
- Find a sunscreen that you like to use so you will wear it often
Comment Reply
I have noticed this increase of highest-ever SPF products as well!
The short answer:
Sunscreen protection increases with higher SPF, but not significantly:
SPF 30 blocks 96.7% of UVB rays
SPF 50 blocks 98.0% of UVB rays
SPF 100 blocks 99.0% of UVB rays
You would assume that SPF 100 would "double" the benefits that SPF 50 provides, but the protection increase is minuscule. The products can claim that there is an increase in protection, which is true, but as you can see, it is only by 1%, and as you get higher numbers, there isn't really a significant difference (except in price!).
The long answer:
Q: How does SPF work?
A: The percentage you see above is based on the formula:
Time needed for a person to burn unprotected vs. time needed for person to burn wearing sunscreen. A person who burns after 30 minutes of unprotected sun exposure is protected 30x more if they had used SPF 30.
Q: How much sunscreen should I use each outing?
A: A full ounce (shot glass full!). Most people use only a half ounce and skimp out on applying the sunscreen. Do you have an almost-full bottle of sunscreen leftover from last summer? If so, you are not using enough at each outing! The sunscreen bottle/tube should last only a few applications, if you are applying it liberally enough. Dermatologists even say that consumers should worry more about applying enough sunscreen instead of how high the SPF is.
A study published in April 2007 in the British Journal of Dermatology found that sunscreen application quantity is an important factor in application, as it is assumed by consumers that if use SPF 100, at least we would be protected with SPF 50, right? What they found: inadequate quantity of application resulted in the protection decreasing to the square root of the SPF. For example, if you use only a half ounce of SPF 100 (vs. recommended full ounce), it does not mean that you have enough coverage of SPF 50, but that you get the protection of only SPF 10 !!
I think this is worth repeating!
According to the British Journal of Dermatology study above:
- Apply ONE OUNCE (shot glass full) of SPF 100 = SPF 100 protection
- Apply only a HALF ounce of SPF = only SPF 10 protection
Q:How often should I re-apply sunscreen?
A: Every 2 hours is ideal, and more often if sweating or in water.
The Environmental Working Group (EWG), 2008, reviewed 1,000 sunscreens, and said that there is a false sense of security with high SPF, because users think they can stay out all day and not re-apply; that they are safe.
This is a great article worth reading:
Sunscreen Investigation, EWG: Sunscreen Summary — What Works and What's Safe
Bottom line:
May 24, 2009 - 7:20am- Make sure your sunscreen protects from both UVB and UVA (some of the higher SPF does not protect adequately from UVA.
- Apply sunscreen liberally: a full shot glass/ounce
- Re-apply every 2 hours
- Find a sunscreen that you like to use so you will wear it often
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