Aluminum potassium sulfate inhibits TRPV1 and TRPA1 activation

Balneotherapy has been used as complementary therapy for many diseases. In Japan, bath salts from the Myoban Spa, which contains a high concentration of aluminum potassium sulfate, have been approved for its analgesic effects. However, the molecular mechanisms underlying the analgesic effects of these ions have not been reported. We focused on TRPV1 and TRPA1, which are known pain sensors. In this study, we evaluated the inhibitory effects of Myoban bath salts and their components, aluminum potassium sulfate and iron sulfate, on TRPV1 and TRPA1 activity using electrophysiological experiments. We found not only bath salts, but also aluminum potassium sulfate inhibited both TRPV1 and TRPA1 activation in the acidic condition. Our study suggested that aluminum potassium sulfate is the main component responsible for the pain–reducing effect of bath salts from the Myoban Spa.