Immediate pigment darkening and persistent pigment darkening as means of measuring the ultraviolet A protection factor in vivo: a comparative study.
BACKGROUND
Persistent pigment darkening (PPD) is a widely used in vivo method for measurement of ultraviolet (UV) A protection factor (UVAPF). However, with increased emphasis on UVA protection and sunscreen products with higher UVAPF gaining popularity, the immediate pigment darkening (IPD) method is drawing attention again. Furthermore, only about a quarter of the recommended quantity of sunscreen is used during daily activities. However, there is as yet no clearly defined relationship between the UVAPF and the amount of sunscreen applied.


OBJECTIVE
To analyse the differences between the IPD and PPD methods, and to establish a relationship between the quantity of sunscreen application and the UVAPF.


METHODS
Different doses of sunscreen were applied on the back of 15 healthy volunteers, and the UVAPF was measured using both the IPD and the PPD methods.


RESULTS
Both methods proved to be effective for measuring the UVAPF. However, all the UVAPF values determined by the PPD method were lower than those determined by the IPD method. Additionally, an exponential relationship between the amount of sunscreen applied and the UVAPF was observed.


CONCLUSIONS
The IPD method can also be used as an appropriate endpoint in the determination of UVA protection. It is time saving, and thus considerably lowers the risk of UV exposure, particularly when testing sunscreen products with higher UVAPF. We further state that in order to achieve the desired protective effect of the sunscreen, the quantity of application is also very important.
Department of Dermatology, Konkuk University School of Medicine, Gwangjin-gu, Seoul 143-729, Korea.
Y J
YJ
Hwang
H J
HJ
Park
H J
HJ
Hahn
J Y
JY
Kim
J H
JH
Ko
Y W
YW
Lee
Y B
YB
Choe
K J
KJ
Ahn
D000328:Adult; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008297:Male; D008875:Middle Aged; D012880:Skin Pigmentation / Q000187:drug effects / Q000528:radiation effects; D013471:Sunburn / Q000517:prevention & control; D013473:Sunscreening Agents / Q000008:administration & dosage / Q000494:pharmacology*; D055107:Suntan / Q000187:drug effects* / Q000528:radiation effects; D014466:Ultraviolet Rays / Q000009:adverse effects*; D055815:Young Adult
D013473:Sunscreening Agents