• elicitation dose–response relationship;
  • methyldibromo glutaronitrile;
  • nickel sulphate;
  • p-phenylenediamine;
  • polysensitization;
  • susceptibility

Summary Background  It is not known if reduced elicitation thresholds are evident among polysensitized individuals when using allergens to which the patients are already sensitized. Reduced elicitation thresholds may be an expression of increased reactivity in this patient group.

Objectives  To examine and compare elicitation dose–response curves and elicitation thresholds in a polysensitized vs. a single/double-sensitized group for allergens to which the test subjects were already sensitized.

Patients/methods  Fifty-one patients (13 polysensitized and 38 single/double-sensitized) were patch tested with nickel sulphate, methyldibromo glutaronitrile (MDBGN) and p-phenylenediamine (PPD) in dilution series. The ratio between the doses eliciting a response in 50% of patients in the two groups was used as the measure for relative sensitivity.

Results  The dose–response curves of the polysensitized group for MDBGN and PPD were shifted to the right, and for nickel sulphate shifted to the left, compared with the single/double-sensitized group. The relative sensitivity for each of the three allergens and a combined relative sensitivity for all three allergens were not significantly different when comparing the polysensitized and single/double-sensitized groups.

Conclusion  No increased sensitivity, in the form of distinct elicitation thresholds, could be demonstrated in polysensitized individuals compared with individuals with one or two contact allergies.