Background: Contact allergy to aluminium (Al) might pose a risk of false-positive readings of patch-test results when testing with Finn chambers. Objectives: To quantify the release of Al from empty Al Finn chambers, covered Finn Aqua chambers, and Al Finn chambers containing different baseline patch-test substances. Methods: Al Finn chambers of different conditions and with different patch-test substances were tested in artificial sweat and their Al release was analyzed by atomic absorption spectroscopy and inductively coupled plasma sector field mass spectrometry. Results: The amount of Al released from empty Finn chambers corresponded to a skin dose of 0.03%–0.5% Al chloride hexahydrate applied in plastic chambers. Although most patch-test substances reduced the release of Al from the Finn chambers due to covering the surface, some substances significantly increased the release of Al from the Finn chambers, most notable for Caine mix II 10% pet., Myroxylon pereirae 25% pet., and sodium tetrachloropalladate hydrate 3.0% pet. Conclusions: The release of Al from Finn chambers corresponds in some cases to clinically relevant concentrations of Al for Al-sensitized individuals.