Importance: Sun-protective behavior affects skin cancer prevention. Shade works by physically shielding skin from direct harmful UV rays; however, skin may still remain exposed to reflected and indirect UV rays. There is no current standard metric to evaluate shade for its effectiveness in sun protection, and there is insufficient clinical evidence that a beach umbrella alone can provide adequate sun protection.
Objective: To directly measure sunburn protection offered by a standard beach umbrella compared with that provided by sunscreen with a high sun protection factor under actual use conditions.
Design, setting, and participants: A single-center, evaluator-blinded, randomized clinical study was conducted from August 13 to 15, 2014, in Lake Lewisville, Texas (elevation, 159 m above sea level), among 81 participants with Fitzpatrick skin types I (n = 1), II (n = 42), and III (n = 38). Participants were randomly assigned to 2 groups: 1 using only a beach umbrella, and the other using only sunscreen with a sun protection factor of 100. All participants remained at a sunny beach for 3½ hours at midday. Clinical sunburn evaluation of each individual for all exposed body sites was conducted 22 to 24 hours after sun exposure.
Interventions: The shade provided by a beach umbrella or protection provided by sunscreen with a sun protection factor of 100.
Main outcomes and measures: Sunburn on all exposed body sites 22 to 24 hours after sun exposure.
Results: Among the 81 participants (25 male and 56 female; mean [SD] age, 41  years) for all body sites evaluated (face, back of neck, upper chest, arms, and legs), the umbrella group showed a statistically significant increase in clinical sunburn scores compared with baseline and had higher postexposure global scores than the sunscreen group (0.75 vs 0.05; P < .001). There was a total of 142 sunburn incidences in the umbrella group vs 17 in the sunscreen group. Thirty-two of the 41 participants (78%) in the umbrella group showed erythema in 1 or more sites vs 10 of the 40 participants (25%) in the sunscreen group (P < .001). Neither umbrella nor sunscreen alone completely prevented sunburn.
Conclusions and relevance: A beach umbrella alone may not provide sufficient protection for extended UV exposure. It is important to educate the public that combining multiple sun protection measures may be needed to achieve optimal protection.
Trial registration: isrctn.org Identifier: ISRCTN19177299.