5. Notice the labeling.
You want sunscreen (not block) that is sweat and water-resistant (not proof). Due to new FDA regulations, no SPF product can be called sunblock, even if this product contains an active ingredient (such as zinc) that is truly a physical block of UVA/ UVB rays. This is due to the consumer misconception that sunblock meant the product was truly blocking the sun and consumers did not need to reapply it. By the end of 2013 will label all SPF products as sunscreens. The same sentiment guided the FDA’s decision to only allow products to be labeled as sweat/water resistant.
Finally, the FDA also created standardized testing so you’ll notice that sunscreens will be certifying themselves as either 40 minute or 80 minute sweat/water resistant. There is no certification higher than 80 minutes due to the requirement that all sunscreen be reapplied every two hours.