Repeated low-dose skin exposure is an effective sensitizing stimulus, a factor to be taken into account in predicting sensitization risk.
BACKGROUND
Contact sensitization by ingredients in personal products is an important clinical problem. It is not clear how sensitization is induced by the generally low concentrations at which they occur but it might be the result of repeated exposure.


OBJECTIVE
To compare the strength of contact sensitization induced by a single exposure to 2,4-dinitrochlorobenzene (DNCB) (60 microg cm(-2)) or three repeated exposures to a subsensitizing dose (10 microg cm(-2)).


METHODS
Two groups (n = 10) of healthy adult volunteers were randomized to receive either a single patch of DNCB 60 microg cm(-2) or three once-weekly applications to the same site of 10 microg cm(-2) DCNB. Four weeks after the last application, sensitization was quantified by measurement of responses (skinfold thickness) to a graded series of four challenge doses.


RESULTS
All the volunteers were sensitized and the strength of the responses was virtually identical between the groups.


CONCLUSIONS
The same degree of sensitization was induced by three exposures to DNCB 10 microg cm(-2) as by one exposure to 60 microg cm(-2) of DNCB. Thus repeated exposure to low doses of contact sensitizers may increase the sensitizing potency. This must be taken into account in future risk assessments.
Paramasivan
P
P
Dermatopharmacology Unit, South Block, Southampton General Hospital, Southampton SO16 6YD, UK.
Lai
C
C
Pickard
C
C
Ardern-Jones
M
M
Healy
E
E
Friedmann
P S
PS
D000328:Adult; D000704:Analysis of Variance; D017449:Dermatitis, Allergic Contact / Q000276:immunology*; D004137:Dinitrochlorobenzene / Q000008:administration & dosage / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007509:Irritants / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D012882:Skin Tests; D055815:Young Adult
D004137:Dinitrochlorobenzene; D007509:Irritants