Which provides better sun protection, sunscreen or a beach umbrella?

This study had a number of important limitations: industry sponsorship, small size, uncertain clinical significance of "sunburn scores," and a somewhat contrived set of study conditions (who doesn't get in the water when you're at the beach on a hot day?). Nevertheless, I think the authors are correct in concluding that an umbrella alone does not provide complete protection from the reflected and diffused ultraviolet (UV) rays that reach the shaded person. This makes some sense since it isn't pitch black under an umbrella. So, slather on that sunscreen, even if you plan to stay under an umbrella. (LOE = 2b)

Ou-Yang H, Jiang LI, Meyer K, Wang SQ, Farberg AS, Rigel DS. Sun protection by beach umbrella vs sunscreen with a high sun protection factor: a randomized controlled trial. JAMA Dermatol 2017;153(3):304-308.  [PMID:28114650]

Randomized controlled trial (single-blinded)

Industry

Uncertain

Population-based

These researchers recruited 81 patients, all of whom spent 3.5 hours at a beach in Texas. The participants are not described at all, an important deficiency in the study, other than that all but one had Fitzpatrick skin type II or III (moderately pale, either European Scandinavian or southern/central European). Half were randomized to receive a standard-sized beach umbrella (just over 6 feet in diameter) and half received an application of sunscreen with a sun protection factor of 100. Participants in the sunscreen group reapplied it an average of twice during the study period. Those under the umbrella were told to stay there, and could only leave it for a total of 30 minutes and only after covering up. Neither group was allowed to enter the water, which seems cruel. The investigators evaluated the exposed areas 24 hours later for the presence of redness or sunburn using a 4-point sunburn score, where 0 indicated no sunburn, 2 indicated defined redness clearly caused by UV rays, and 4 meant edema and/or blisters. The global sunburn score was more likely to increase (worsen) in the umbrella group, and there were more sunburned body sites in the umbrella group than in the sunscreen group (142 vs 17). This study was sponsored and conducted by Johnson & Johnson, the manufacturer of Neutrogena sunscreens and skin care products.