Alas, there are no trips to Tahiti for our sunscreen panelists--they go to a lab. In UVB tests, sunscreen is applied to a rectangular area of panelists' backs. They soak in a tub of water and then six spots are exposed for set times to UVB radiation from a sun simulator. About a day later, the six spots are examined for redness. The resulting UVB Ratings reflect each product's actual effectiveness, not how close it came to meeting its SPF claim. To test for UVA protection, we follow the same process using a different group of panelists but we use UVA rays and check for tanning instead of redness.
In addition, we use a test based on the Food and Drug Administration's "critical wavelength" test, required for sunscreens that claim broad-spectrum protection. It assesses how well UV rays are absorbed by clear plastic plates treated with sunscreen. Two products came in slightly below the critical wavelength threshold in our tests. (Results can vary depending on the nature of the plates used.) The critical wavelength results are not used in the UVA ratings.
Overall scores are based on results of the above UVB and UVA tests.
For the moisturizers with sunscreen, we followed the same procedures, but we did not test after water immersion because these products don't claim to be water resistant.
Finally, we have our trained sensory panel evaluate the scent and skin feel of the products.