What You Need to Know About Sun Screen SPF

The sun is trying to finally come out today in NYC so I thought it wold be a good time to share more research I’ve found about sunscreen brands and important things to know and understand about SPF. I keep finding more and more interesting information so I’m going to again split up the posts to allow for more focus and try not to overwhelm. My next post on this topic will cover the different brands.

What is SPF:

From Wikipedia on SPF:

The SPF of a sunscreen is a laboratory measure of the effectiveness of sunscreen — the higher the SPF, the more protection a sunscreen offers against UV-B (the ultraviolet radiation that causes sunburn). There are two systems for SPF. American SPF numbers are double the SPF numbers on European products.[citation needed] An American SPF 20 sunscreen is the same as SPF 10 in Europe. It is not always clear on the packaging which system is being used.

The SPF indicates the time a person with sunscreen applied can be exposed to sunlight before getting sunburn relative to the time a person without sunscreen can be exposed. [This is the American measurement of SPF] This assumes constant solar intensity over the time period. On any day, someone who would burn after 12 minutes in the sun would expect to burn after 120 minutes if protected by a sunscreen with SPF 10, using the American system, or SPF 5, using the European system.

SPF: How High? - a WebMD.com slideshow has a blurb explaining that the minimum recommended SPF should be SPF 30 US/SPF 15 Europe.

“Anything higher than SPF 30 isn’t going to make a dramatic improvement on your UV protection,” Colbert says. SPF 15 deflects 93% of UV rays while SPF 30 fends off 97%. After that the coverage goes up in small increments until you reach SPF 50 with 99% defense. And wearing the higher number may give you a false sense of security, Colbert warns.”

The New York Times just had an article on May 13, 2009 by Catherine Saint Louis Confused by SPF? Take a Number that digs into the number questions. Basically, the SPF 30 is still a magic number verses higher ones out now such as 85 and even 100. There are some who argue that over a lifetime the extra few percentages of protection can add up.

European SPF vs American SPF

I agree that there should be a citation in the Wiki entry above about the differences in Euro/American SPFs. Yet, according to many articles including this article, http://www.netdoctor.co.uk/travelhealth/sunbathing.htm (note a UK site):

There are two systems for specifying a sunscreen’s protection. American SPF numbers are double the SPF numbers on European products. An American SPF 20 sunscreen is the same as SPF 10 in Europe. SPF is a laboratory measure of effectiveness. The European SPF system is based on the time a person with pale skin can remain in the sun without getting red and tender. This is usually 20 minutes in spring.

In summary, it is true that determining which SPF measuring system is being used is hard to figure out. I have looked on both American and European products and it isn’t clearly marked yet I think it’s safe to assume that if the product is made in the US or the company is American they are using the American system and If the product is made in Europe and/or a European brand you can assume they are using the European SPF system of measurement. Ex: I bought Weleda Children’s Sun Screen from Whole Foods the other day in NYC with a SPF 18. At first I almost didn’t buy it because the SPF was 18, then I remembered it was Swiss and they were using the European system meaning the SPF would be about SPF 36 with the American system.

The European SPF system is based on the time a person with pale skin can remain in the sun without getting red and tender according to website netdoctor.co.uk article. According to Wikipedia, American SPF is measured by the time a person with sunscreen applied can be exposed to sunlight before getting sunburn relative to the time a person without sunscreen can be exposed.