Matsunoyama Onsen’s Curative Properties

Matsunoyama Onsen ranks among Japan's Three Great Curative Springs, and the claim holds up on paper. The water meets therapeutic thresholds for eight of the nineteen minerals Japanese law requires for hot spring certification, including the country's highest levels of antibacterial boric acid. The source is seawater trapped underground by tectonic activity about 12 million years ago. That ancient seawater is highly saline and hypertonic, meaning minerals absorb through the skin during bathing. A buoyant feeling in the tub and warmth that lingers for hours afterward are two things bathers consistently notice.