Dose-response and time-course characteristics of UV-A1 erythema.
OBJECTIVE
To determine the time course and dose-response characteristics of UV-A1 erythema in the Tayside region of Scotland.


METHODS
Adult volunteers (skin types I and II [n = 13] and III and IV [n = 11]) were exposed to geometric dose series of UV-A1 irradiation from a high-output source on photoprotected lower back and inner forearm skin.


METHODS
Photobiology unit in a university hospital.


METHODS
The minimal erythema dose (MED) was recorded visually and erythema was assessed objectively by erythema meter at 4, 8, 24, and 48 hours after exposure.


RESULTS
Peak erythema (lowest visual MED) was seen at 8 hours on the back and arm in 11 subjects with skin types I and II and on the back at 8 hours in 9 subjects and on the arm at 4 hours in 10 subjects with skin types III and IV. The lowest median (range) MED was 20 J/cm(2) (14-56 J/cm(2)) on the back and 42 J/cm(2) (20 to >80 J/cm(2)) on the arm at 8 hours for subjects with skin types I and II and 28 J/cm(2) (20-112 J/cm(2)) at 8 hours on the back and 56 J/cm(2) (28-80 J/cm(2)) at 4 hours on the arm for subjects with skin types III and IV. The D(0.025), an objective measure that corresponds approximately to the visual MED, demonstrated a broad peak from 8 to 24 hours.


CONCLUSIONS
Our local population is more erythemally sensitive to UV-A1 radiation than reports suggest. Daily dose regimens may risk cumulative erythema. Lower starting doses should be used in this population. The wide range of MEDs highlights the need for MED testing.
Beattie
Paula E
PE
Photobiology Unit, Dermatology Department, University of Dundee, Ninewells Hospital and Medical School, Ninewells Avenue, Dundee DD1 9SY, Scotland. paula_e_beattie@hotmail.com
Dawe
Robert S
RS
Ferguson
James
J
Ibbotson
Sally H
SH
D000328:Adult; D001132:Arm; D001415:Back; D004307:Dose-Response Relationship, Radiation; D004890:Erythema / Q000209:etiology*; D006785:Hospitals, University; D006801:Humans; D008875:Middle Aged; D012606:Scotland; D012880:Skin Pigmentation; D013997:Time Factors; D014466:Ultraviolet Rays / Q000009:adverse effects*