Patch testing with palladium and aluminium, epidemiological and experimental studies

Abstract
The aim of this thesis was to investigate the prevalence and significance of contact allergy to palladium from a Swedish perspective. Our initial findings made it necessary to also explore the importance of the metal aluminium used in test chamber systems and the effect of aluminium chloride (Al-Cl) in patch test preparations.
A retrospective study (study I), with 18,306 patch test results obtained from 1995-2016 showed that the prevalence of contact allergy to palladium is following that of nickel. After the introduction of the EU Nickel Directive in 2001, there was a significant decrease in contact allergy to sodium tetrachloropalladate (Na-PdCl), palladium chloride (Pd-Cl), and nickel sulphate (Ni) among younger females, age six to 30 years. Regression analysis revealed that women with contact allergy to Ni were approximately 36 times more likely to have contact allergy to Pd-Cl compared to females with no allergy to Ni.
The prevalence of isolated palladium (Pd) allergy in the whole study population (men and women) was 1.4% and remained stable from 1995 to 2016.
In study II, Na-PdCl showed less variability in patch test results, compared to Pd-Cl. When re-testing the same 15 participants with known contact allergy to Ni, Na-PdCl, and Pd-Cl, a seasonal variation was seen. In wintertime, there were significantly higher summarised test scores compared to in late summertime for the three metal salts Pd-Cl, Na-PdCl, and Ni.
A retrospective study (study III) showed that the use of Finn Chambers in patients with contact allergy to aluminium could be a risk for false-positive patch test reactions to Na-PdCl and Pd-Cl. No such risk was seen in patients tested with Finn Chamber Aqua.
In study IV, the use of Al-Cl in test preparations with Ni seemed to increase the sensitivity for detecting Ni allergy. When adding 30.0% Al-Cl to Ni 15.0% aqua, the sensitivity increased to 91% from 50.0% in Ni 5.0% in petrolatum. This increase in sensitivity was only seen when adding Al-Cl to Ni and was not seen when adding Al-Cl to methylisothiazolinone and to fragrance mix I.