Sunscreen use optimized by two consecutive applications

Abstract

Sunscreen users are often inadequately protected and become sunburned. This study aimed to investigate how much two consecutive sunscreen applications increased the quantity of sunscreen applied and decreased the skin area left without sunscreen (missed area) compared to a single application. Thirty-one healthy volunteers wearing swimwear were included and applied sunscreen two consecutive times in a laboratory environment. Participants had pictures taken in black light before and after each application. As sunscreens absorb black light, the darkness of the skin increased with increasing amounts of sunscreen applied. We conducted a standard curve establishing a link between change in picture darkness and quantity of sunscreen. The quantity of sunscreen at selected skin sites as well as the percentage of missed area was determined after each application. Participants had missed a median of 20% of their available body surface after a single application. After double application they had missed 9%. The decrease in missed areas was significant for the whole body surface and for each of the body regions separately. The median participant had applied between 13% and 100% more sunscreen at the selected skin sites after double application than after single application. We recommend double application, especially before intense sun exposure.

Sunscreen Application, Safety, and Sun Protection: The Evidence

“…Several studies have addressed sunscreen reapplication. Heerfordt showed that double sunscreen application optimizes sunscreen use compared with a single application as the median participant had applied between 13% and 100% more sunscreen at the selected skin sites after double application than single application 51 . In a study of 30 office workers, where half were randomly assigned to having SPF 15-30 sunscreen reapplied after 3 hours, no significant difference in absorption readings (taken at 20 minutes and then hourly for 1-6 hours after initial application) was found in the reapplication group 52 .…”

Ações de fotoeducação em saúde no ambiente escolar como estratégia para a prevenção de fotodermatoses

“…Quanto maior a percepção dos benefícios da fotoproteção, maior o FPS utilizado (Cokkinides et al, 2001). O uso correto do fotoprotetor, isto é, seu emprego diário, com aplicação 20 minutos antes da exposição solar e reaplicações a cada duas horas, é uma das medidas que devem ser constantemente estimuladas (Heerfordt et al, 2018).…”

Promoting sunscreen use in adolescents playing outdoor sports using UV detection stickers

“…A previous study of Australian outdoor sport players (n = 237) had found 47% of the participants used sunscreen inadequately and 30% reported not using sunscreen ( Berndt et al, 2010 ). Heerfordt et al (2018) has also shown using UV camera technology that two consecutive sunscreen applications improved sunscreen coverage reducing missed areas. Guidance on the application and re-application of sunscreen is warranted and wearable UV detection stickers can provide tailored and personalised information to the user in-the-moment where it is most useful ( Heron and Smyth, 2010 ).…”