• contact allergy;
  • contact sensitization;
  • fragrance mix;
  • nickel sulfate;
  • patch test reactions

Background:  Patch test patients have two or more positive reactions to unrelated allergens more often than to be expected by chance. This study evaluates synchronous patch test reactions to test the hypothesis that in such cases an allergen-independent disposition for contact sensitization may be involved.

Methods:  Data of 87 834 patients tested with a standard patch test series in 42 centers of a Central European Network were retrospectively evaluated. Analyses were done for synchronous positive reactions of graded strength to nickel sulfate, fragrance mix, and to those five allergens that followed in frequency of positive results. All seven allergens selected were not related by chemical structure or exposure. Descriptive univariate and bivariate analyses as well as a polytomous logistic regression analysis were performed. Odds ratios with 95% confidence intervals were calculated.

Results:  With an increasing strength of a positive reaction to nickel or to fragrance mix the likelihood of further positive reactions to unrelated contact allergens increased significantly, and the mean strength of such additional reactions raised steadily with an increasing strength of a nickel or fragrance reaction.

Conclusions:  Our findings support the idea that patients who respond with a strong patch test reaction may have a particular general disposition to acquire contact sensitivity to additional unrelated allergens. They should therefore not only be advised to avoid their known allergen but in addition to minimize exposure other contact allergens.