Contact allergy trends in Sweden - a retrospective comparison of patch test data from 1992, 2000, and 2009

Background. Contact allergy prevalence rates change over time as a result of variations in allergen exposure. Data from patch test clinics are often used as markers for allergy trends. Objectives. The aim of the present retrospective study was to describe trends in rates of sensitization to allergens in the Swedish baseline series. Patients/materials/methods. Prevalence rates are described by comparing consecutive patch test data from 1992, 2000 and 2009 in Swedish patch test clinics. In total, 3680 patients were included in 1992, 3825 in 2000, and 3112 in 2009. Results. Among test substances with a sensitization rate above 2% in 2009, significant decreases were noted for nickel sulfate, cobalt chloride, colophonium, and methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI), and a significant increase for p-phenylenediamine, as compared with 1992. Potassium dichromate reactions had increased among younger women, whereas reactions to nickel and cobalt had decreased in this group. Sensitization to chromium, cobalt and fragrance mix I had decreased among older men, and sensitization to nickel had decreased among younger men. Conclusions. It is probable that these changes in 1992-2009 reflect both changes in regulations for nickel, lower levels of chromium in cement and of MCI/MI in cosmetics, and increasing use of hair dyes.