Effects of aluminium chloride added to common patch test substances

Background: A modulating effect of aluminium regarding type IV reactions might exist but has not been further investigated. Objectives: The aim of this study was to investigate the effect on patch test reactions when adding aluminium chloride hexahydrate (Al-Cl) to common test preparations. Materials and methods: Al-Cl in different concentrations was added to nickel sulphate 15.0% aqua (Ni), methylisothiazolinone 0.2% aqua (MI) and fragrance mix I 10.0% aqua/ethanol (FM I). The Ni preparations were tested in 120 consecutive patients. MI and FM I were tested in participants known to have contact allergy to the respective allergen. McNemar's test was used to decide which Ni preparation had the highest sensitivity. Wilcoxon signed-rank test was used to calculate pairwise comparison in summarized test score for the preparations with MI and FM I. Results: Adding Al-Cl 20.0%/30.0% to Ni identified twice as many patients with contact allergy to nickel compared to Ni without Al-Cl. Adding Al-Cl 20.0%/10.0% to MI, decreased the patch test reactivity compared to MI without Al-Cl. No differences in patch reactivity were noticed when adding Al-Cl to FM I. Conclusion: Al-Cl 20.0% or 30.0% seems to enhance the patch test reactivity to Ni 15.0% aqua.