Testing SPF 15–100, Indoor vs. Outdoor

Sep 1, 2013 | Contact Author | By: Dennis Lott, Florida Suncare Testing Inc.
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Title: Testing SPF 15–100, Indoor vs. Outdoor
outdoorx SPFx natural sunlightx MEDx
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Keywords: outdoor | SPF | natural sunlight | MED

Abstract: Lab tests on sunscreens show it takes more energy to produce mild erythema on protected skin than unprotected skin. Yet the FDA questions the need for SPFs higher than 50. In response, two outdoor studies were conducted using commercial products to challenge standing premises and determine if there is a measurable difference in an SPF 100 and SPFs of 50 or less.

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D Lott, Testing SPF 15–100, Indoor vs. Outdoor

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In June of 2011, the U.S. Food and Drug Administration (FDA) published its report, Revised Effectiveness Determination: Sunscreen Drug Products for Over-the-counter Human Use, 21 CFR part 201.1 This stated, “The record does not currently contain sufficient data to indicate that there is additional clinical benefit above SPF 50.” However, the FDA invited submissions for data demonstrating the contrary. In response, this author submitted test data showing that a group of four commercial products with SPFs between 70 and 85 protected individuals better than a group of four commercial products with SPFs from 50 to 55.2

By definition, the FDA’s clinical method1 to test sunscreens indicates an SPF of 100 requires twice as much erythemal UV energy as an SPF 50 to produce the same effect. Yet many argue there is no clinical difference between the two, and that consumers are equally protected by either. In fact, as this article was written, an Internet search for “What SPF is needed?” retrieved three articles in which dermatologists stated: 1. The difference in UVB protection between an SPF 100 and SPF 50 is marginal; far from offering double the blockage, SPF 100 blocks 99 percent of UVB rays, while SPF 50 blocks 98 percent. (SPF 30, that old-timer, holds its own, deflecting 96.7 percent).3 2. It is logical for someone to think that an SPF of 30 is twice as good as an SPF of 15, and so on, but that is not how it works;4 and 3. Actually, an SPF 70 doesn’t protect you that much better than a SPF 30.5

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Table 1. Commercial product % actives by SPF

Table 1. Commercial product % actives by SPF

Three commercial sunscreen products with SPF levels of 30, 50 and 100 were used in the first test, and the same SPF 50 and 100 products were used in the second test—in addition to an SPF 45.

Table 2. First study MED and accumulated MED readings in 15-min increments

Table 2. First study MED and accumulated MED readings in  15-min increments

Table 2 shows the MED and accumulated MED readings in 15-min increments, whereas Table 3 illustrates the grades obtained for each subject for each product or unprotected site.

Table 3. Grades obtained for each subject, for each product or unprotected site

Table 3. Grades obtained for each subject, for each product or unprotected site

Table 2 shows the MED and accumulated MED readings in 15-min increments, whereas Table 3 illustrates the grades obtained for each subject for each product or unprotected site.

Table 4. Estimates the SPF based on the erythemal energy at the product sites, divided by the same grade on the unprotected site

Table 4. Estimates the SPF based on the erythemal energy at the product sites, divided by the same grade on the unprotected site

Table 4 estimates the SPF based on the erythemal energy at the product sites, divided by the same grade on the unprotected site.

Table 5. Second outdoor study

Table 5. Second outdoor study

Table 5  displays the MED and accumulated MED readings in 5-min increments, the UVA readings in mw/cm2, as well as temperature, relative humidity, wind speed and comments.

Table 6. Second study grade summary

Table 6. Second study grade summary

Table 6 illustrates the grades obtained for each subject with each product or unprotected site.

Figure 1. Subject 2’s right leg shows erythema in both sites; upper site = unprotected, lower site = SPF 50

Figure 1. Subject 2’s right leg shows erythema in both sites; upper site = unprotected, lower site = SPF 50

Figure 1 is a photo of Subject 2’s right leg, illustrating erythema on both sites.

Figure 2. Subject 7’s right leg, illustrating erythema in both sites

Figure 2. Subject 7’s right leg, illustrating erythema in both sites

Figure 2 is a photo of Subject 7’s right leg, illustrating erythema in both sites.

Footnotes (CT1309 Lott)

a The PMA 2100 radiometer equipped with a 2102 outdoor detector is manufactured by Solar Light Co., www.solarlight.com.

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