Dake Onsen

Dake Onsen sits in the mountains above Nihonmatsu City in Fukushima Prefecture, accessible by bus from Nihonmatsu Station on the Tohoku Main Line. The road climbs steeply through cedar and broadleaf forest, and the village that appears after twenty minutes of climbing is compact and weathered, a row of small inns along a mountain stream that feels like it has been doing business here for a long time. The springs are said to have a twelve-hundred-year history, though the modern town dates more clearly to the Edo period, when the hot spring was used to treat injuries and skin conditions.

The water at Dake is strongly acidic sulfur, with a pH of 2.5, which puts it among the most acidic bathing springs in Japan. At that level of acidity the water has a sharp, vinegar-like quality on the skin that initially feels surprising. The sulfur smell is present and direct, not the background note you find at milder springs. The water comes out of the source at up to 90 degrees Celsius, and by the time it travels through several kilometers of pipe from the actual vent to the village baths, the temperature moderates and the acid quality softens slightly. The resulting bath is a milky yellow-white, warm and distinctly cleansing on the skin.

The acidity that seems alarming on paper is actually the reason Dake has been valued for skin conditions for centuries. At pH 2.5 the water has a strong antibacterial effect, and longtime visitors claim significant improvement in psoriasis, eczema, and chronic skin inflammation after repeated soaks. You rinse thoroughly after bathing here, unlike at alkaline springs where the residue is part of the benefit. Adatara, the mountain directly above the village, is a volcano that last erupted in 1900, and the spring source is on the flanks of a still-active geothermal zone. Looking up at the peak from the outdoor tub while the acidic water works on your skin, that connection between the hot earth and the bath in front of you is direct and obvious.

The village has a particular Showa-era atmosphere that many visitors find unexpectedly appealing. The inns are not luxury establishments. The decor runs to worn woodwork, floral wallpaper, and communal dining rooms where the food is Tohoku mountain cooking: wild mountain vegetables, pickled things, grilled local fish. The schedule is organized around bathing and meals, which is all it was ever organized around. Nihonmatsu's famous Adatara Highland and the chrysanthemum festival in October are additional reasons to time a visit to this corner of Fukushima, but the spring itself is reason enough.