Ke. Andersen et al., The time-dose-response relationship for elicitation of contact dermatitis in isoeugenol allergic individuals, TOX APPL PH, 170(3), 2001, pp. 166-171
The elicitation response in allergic contact dermatitis is dose dependent,
but the time-concentration relationship for elicitation has not previously
been described. In this study 27 isoeugenol-sensitive patients participated
in serial dilution patch tests with isoeugenol and a double-blinded Repeat
ed Open Application Test (ROAT) using two concentrations of isoeugenol, 0.2
and 0.05%, Seven controls without isoeugenol allergy were also included. T
he participants applied 3.72 +/- 1.57 (mean +/- SD) mg/cm(2) of coded isoeu
genol solutions twice a day to a 3 x 3 cm(2) area on the volar aspect of th
e right and left arm, respectively. For each test site the applications con
tinued until a reaction appeared or for a maximum of 28 days. The minimal c
riteria for a positive reaction regarded as allergic contact dermatitis was
persistent erythema at the ROAT test site. All controls were negative and
16/24 (66.7%) of the included isoeugenol-sensitive subjects showed a positi
ve ROAT to the 0.2% solution within the study period (Fisher's test, p = 0.
0024). Ten of the positive patients also reacted to the 0.05% solution. The
median number of days until a positive reaction to the 0.2% solution was 7
days and was 15 days for the 0.05% solution. There was a highly significan
t correlation between the patients' patch test threshold and the number of
days until a positive ROAT. In conclusion, the time until an isoeugenol all
ergic individual reacts in a ROAT depends on the individual sensitivity as
well as the exposure concentrations; for low concentrations of the allergen
or low degree of sensitivity, the allergic contact dermatitis may develop
after several weeks of exposure. Therefore, a negative ROAT after 7 days ma
y be a false negative. (C) 2001 Academic Press.