Now In: Sun Protection Factor: SPF Sunscreen Info by Badger
About SPF Sunscreen Ratings
In Brief
|
SPF measures sunscreen protection from UVB rays, the kind that cause sunburn and contribute to skin cancer.
|
SPF does not tell you how well a sunscreen will protect from UVA rays which are also damaging and dangerous.
|
Most dermatologist recommend using a sunscreen with an SPF of 15 or 30. Higher SPFs don't give much more protection.
|
 SPF, or Sunburn Protection Factor, is a measure of how well a sunscreen will protect skin from UVB rays, the kind of radiation that causes sunburn and can contribute to skin cancer.
- If your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen would allow you to stay in the sun without burning for approximately 150 minutes (a factor of 15 times longer). This is a rough estimate and depends on skin type, intensity of sunlight and amount of sunscreen used.
- For best protection, experts recommend using a sunscreen with a minimum SPF rating of 15, applying the proper amount (2mg/cm2 of skin, or about one ounce for full body coverage) and reapplying every 2 hours.
- Most people under-apply sunscreens, using ¼ to ½ the amount required. Using half the required amount of sunscreen only provides the square root of the SPF. So, a half application of an SPF30 sunscreen only provides an effective SPF of 5.5!
The SPF scale is not linear:
- SPF15 blocks 93% of UVB rays
- SPF30 blocks 97% of UVB rays
- SPF50 blocks 98% of UVB rays
So, one way of looking at this is that SPF30 sunscreen only gives you 4% more protection than SPF15 sunscreen.
Or, another way of looking at it is:
- SPF15 (93% protection) allows 7 out of 100 photons through
- SPF30 (97% protection) allows 3 out of 100 photons through.
So, while you may not be doubling your level of protection, an SPF30 will block half the radiation that an SPF15 would let through to your skin.
It’s complicated, but to keep it simple, most dermatologists recommend using an SPF15 or SPF30 sunscreen.
Why not use a really high SPF? Sunscreens with really high SPFs, like SPF75 or SPF100, do not offer significantly greater protection than and SPF30 and are thought to mislead people into thinking they have more protection than they actually do. Because of this, the FDA does not allow any sunscreen to be labeled as anything higher than SPF30+. Currently any sunscreen labeled with and SPF greater than 30+ (or without a 'Drug Facts' label) is 'misbranded' under Section 502 of the Federal Food, Drug & Cosmetic Act. The FDA is planning to increase the maximum stated SPF to 50+ in the near future.
Remember, SPF is only a measure of how well a sunscreen will protect you from UVB rays. To learn about the dangers of UVA rays and how to protect yourself from them, visit our Broad Spectrum UVA Protection page.
Read more about SPF Sunscreens:
FDA's page on Sun Protection
Mayo Clinic's Sunscreen Information
|
