Temporal trends of preservative allergy in Denmark (1985-2008).

Background: Most cosmetics and industrial products contain preservatives. Preservative allergy is common and, historically, changing contact allergy epidemics caused by preservatives have been observed. In 1997, Alan Dillarstone predicted a stable development of preservative allergy following mandatory ingredient labelling on cosmetic products.
Objectives: To investigate the development in the prevalence of preservative allergy in Denmark over a 24-year period (1985-2008) and to challenge the prediction made by Dillarstone.
Patients/methods: A retrospective analysis of patch test data was performed (n = 18179). Comparisons were made using a chi(2) test. Logistic regression analyses were used to test for associations.
Results: The development of preservative allergy mirrored those of other European patch test centres. The development was not dependent on sex or age group. The prevalence was higher among women and those aged 41-60 years. Formaldehyde allergy was persistently prevalent over the study years. The overall prevalence of preservative allergy increased significantly (P(trend) = 0.001), mainly because of patch testing with additional preservatives in recent years.
Conclusions: Dillarstone's prediction was confirmed as the prevalence of contact allergy to individual preservatives remained relatively stable. However, the overall burden of preservative allergy seemed to increase. Introduction of new preservatives may add to the burden of contact allergy.