Photodermatol Photoimmunol Photomed. 2018;34:117–121. wileyonlinelibrary.com/journal/phpp
© 2017 John Wiley & Sons A/S.
Published by John Wiley & Sons Ltd
Accepted: 5 December 2017
Photoprotection by sunscreen depends on time spent on
Ida M. Heerfordt | Linnea R. Torsnes | Peter A. Philipsen | Hans Christian Wulf
Department of Dermatology, Bispbjerg
Hospital, University of Copenhagen,
Ida M. Heerfordt, Department of
Dermatology, Bispbjerg Hospital, University of
Copenhagen, Copenhagen, Denmark.
Sunscreen was provided free of charge by
Galderma. Except for this, the study was
funded solely by Bispbebjerg Hospital
Background: To be effective, sunscreens must be applied in a sufficient quantity and
reapplication is recommended. No previous study has investigated whether time spent
on sunscreen application is important for the achieved photoprotection.
Aim: To determine whether time spent on sunscreen application is related to the
amount of sunscreen used during a first and second application.
Methods: Thirty- one volunteers wearing swimwear applied sunscreen twice in a labo-
ratory environment. Time spent and the amount of sunscreen used during each ap-
plication was measured. Subjects’ body surface area accessible for sunscreen
application (BSA) was estimated from their height, weight and swimwear worn. The
average applied quantity of sunscreen after each application was calculated.
Results: Subjects spent on average 4 minutes and 15 seconds on the first application
and approximately 85% of that time on the second application. There was a linear re-
lationship between time spent on application and amount of sunscreen used during
both the first and the second application (P < .0001). Participants applied 2.21 grams
of sunscreen per minute during both applications. After the first application, subjects
had applied a mean quantity of sunscreen of 0.71 mg/cm
on the BSA, and after the
second application, a mean total quantity of 1.27 mg/cm
had been applied.
Conclusion: We found that participants applied a constant amount of sunscreen per
minute during both a first and a second application. Measurement of time spent on
application of sunscreen on different body sites may be useful in investigating the
distribution of sunscreen in real- life settings.
sun protection, sunscreen application, sunscreen use
1 | BACKGROUND
Sunscreen is one among a number of methods to protect the skin
against ultraviolet (UV) radiation from the sun, which is the primary
cause of skin cancer.
To be effective, sunscreen must be applied
in a adequate quantity on all exposed body sites, and studies have
documented that sunscreen users often gain insufficient protection
resulting in sunburn.
When determining the sunscreen protection
factor (SPF), a quantity of 2 mg/cm
is applied, but in real life only,
0.5- 1.0 mg/cm
which may be one of the explanations for
Another reason could be that certain exposed
skin areas are left without sunscreen.
Repeated application of sun-
screen has been recommended to address these problems.
Studies have found relations between time spent on tooth brush-
ing and plaque control
and furthermore between time spent on
washing hands and reduction in number of bacteria.
No study to
date has investigated a possible relation between time spent on sun-
screen application and the amount of sunscreen applied.
Our study aimed to determine whether time spent on sunscreen
application is related to the amount of sunscreen applied during a first