Simple Spring

Springs that contain less than 1,000 mg of dissolved solids (excluding gaseous solids) per kilogram of thermal water and whose temperature in the spring is 25° C or higher. Those that have a pH equal to or greater than 8.5 are called “simple alkaline springs.”  

The feel is soft on the skin. It is odorless and generates little skin irritation. When in contact with its alkaline version, the skin acquires a silky sensation, giving the impression of turning softer and smoother.

An immersion bath is recommended to help treat dysfunctions of the autonomic nervous system, such as blood pressure, insomnia and depression.

Carbon Dioxide Spring

Springs that contain 1,000 mg or more of free carbon (carbon dioxide) per kilogram of thermal water.

While in the water, bubbles of carbon dioxide stick to the body, providing a refreshing, comforting sensation. However, the carbon dioxide can dissipate if the water is heated. These waters stimulate circulation and support the healing of cuts and wounds and are recommended for peripheral arterial disease and autonomic nervous system dysfunctions.

When ingested, it provides a pleasant and refreshing sensation to the palate, which is why it is recommended to assist in the treatment of gastrointestinal dysfunctions.

A relatively rare spring in Japan, it is popularly known as Awa no Yu ("Bubbling Water").

Bicarbonated Spring

Springs that contain 1,000 mg or more of dissolved solids (excluding gases) per kilogram of thermal water and whose main component of negative ions is bicarbonate. They may also contain calcium, magnesium or sodium. In those that contain calcium, there may be deposit formations and calcareous precipitates in the actual spring.

Its composition is beneficial for the healing of cuts and wounds and in the treatment of peripheral arterial disease, in addition to softening the dryness of the skin.

Chloride Spring

Springs that contain 1,000 mg or more of dissolved solids (excluding gases) per kilogram of thermal water and whose main component of negative ions is chloride. They may also contain sodium, calcium or magnesium, depending on the composition of the ions present in the water.

These springs are relatively common in Japan. Because it has salt as its main component, it acquires a salty taste on the palate. In cases where the salt concentration is high or in the presence of magnesium, the water takes on a bitter taste. 

Bathing in it helps healing and attenuates skin dryness, and is also recommended in cases of peripheral arterial disease and depressive conditions.

Iodine Spring

Springs that contain 10 mg or more of iodine per kilogram of thermal water. It is common in non-volcanic hot springs and acquires a yellowish hue over time.

Its ingestion is recommended to aid in the treatment of cholesterol.

Sulphate Spring

Springs that contain 1,000 mg or more of dissolved solids (excluding gases) per kilogram of thermal water and whose main component of negative ions is sulphate.

Bathing in it helps healing and attenuates skin dryness, and is also recommended in cases of peripheral arterial disease and depressive conditions. And its ingestion is related to combating biliary disorders, high cholesterol levels and constipation.

Iron Spring

Springs that contain 20 mg or more of total iron (iron ii) ions per kilogram of thermal water. Due to this composition, its ingestion is recommended as an aid in treating anemia.

According to the presence of the negative ion, it is classified as bicarbonated or sulfate.

When these waters reach the surface and come into contact with the air, the iron present in their composition oxidizes and the thermal water takes on a reddish-brown color.

Sulfur Spring

Springs that contain 2 mg or more of sulfur per kilogram of thermal water. Containing hydrogen sulfide, it is a relatively common hot spring in Japan.

The peculiar, rotten egg-like odor is caused by the hydrogen sulfide.

Bathing in it is beneficial for the treatment of skin diseases such as atopic dermatitis, psoriasis, chronic eczema and pyoderma.

Acidic Spring

Springs that contain 1 mg or more of hydrogen ions per kilogram of thermal water.

Its acidity is apparent on the palate and possesses antibacterial properties.

Radioactive Spring

Springs that contain 30 x 10 ⁰ ¹⁰ Curie (or 8.25 Mache units) or more of radon per kilogram of thermal water.

Although radioactivity is often associated with harmful effects on the human body, the amount present in this source is negligible, being significantly lower than that generated during an x-ray, for example.

Extremely low doses of radioactivity have been shown to provide beneficial effects to the human body and may aid in the treatment of diseases such as rheumatoid arthritis and ankylosing spondylitis.