Simple Onsen｜ Sulphur Onsen ｜ Chloride Onsen ｜ Ferruginous Onsen ｜
Cupriferous / Ferruginous Onsen ｜ Aluminium Onse
Acidic Onsen ｜ Bicarbonate Onsen ｜
Carbon Dioxide Onsen ｜ Radioactive Mineral Onsen ｜ Sulphate Onsen
List of onsen properties/effects
| Characteristics | Mild and gentle on the skin. Colourless and transparent, tasteless and odorless. |
|---|---|
| Elements | Elements differ from onsen to onsen. Low mineral and gas content (less than 1g per 1kg of onsen) |
| Effects | General ailments such as neuralgia, muscle/joint pain, bruises, sprains, sensitivity to cold, relief from fatigue, overall health promotion, etc. |
Simple onsen is easily misunderstood as being “just hot water with few components, low quality onsen” but “simple onsen” refers only to the element content level not to the types of elements. Even though they are all called “simple onsen”, easy comparison or classification of each onsen is not possible as there are so many diverse properties. By comparing element composition, the qualities of each type of onsen may be grouped as below but onsen with well-balanced properties that contain small amounts of various elements also exist.
| Characteristics | High temperature. Cloudy with an odour similar to that of bad eggs. |
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| Elements | Contains high levels of sulphur or hydrogen sulphide |
| Effects | Acne, oily skin, dermatitis, rheumatism, asthma, gynaecological disorders, etc. It stimulates the production of insulin so it also effective for the symptoms of diabetes. |
Hydrogen sulphide is a toxic substance that is highly irritant to mucous membranes, skin and respiratory organs. Those who are ill or convalescing and who have lost physical strength or those with dry skin should be particularly careful and there are some cases in which bathing is unsuitable for rheumatism and asthma patients. Such patients who wish to bathe in a sulphur onsen should discuss this with their doctor first. As hydrogen sulphide affects metals adversely, metal accessories other than those made of gold or platinum should not be worn while bathing. It has, in particular, a considerable reaction to silver causing it to tarnish and blacken.
| Characteristics | Mild and gentle on the skin. Colourless and transparent, tasteless and odorless. |
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| Elements | Contains salts, in particular high levels of common salt. Over 1,000mg of dissolved element per 1kg of onsen of which the main element of anions is chloride ions. |
| Effects | External wounds, chronic dermatitis, bruises, sprains, chronic rheumatism, infertility, gout, vascular sclerosis, etc. |
As they contain salts, in particular high levels of common salt, these are also called Salt Onsen.
| Characteristics | As the iron in the water oxidizes when it comes into contact with the air, the water has a reddish-brown colour. |
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| Elements | Contains iron carbonate / iron sulphate. |
| Effects | Sterilizing effect, anaemia, kidney trouble, gastrointestinal disorders, joint pain, dermatitis, menopausal disorders, etc. Good moisturizing effect, heats the body well. |
The majority of onsen that are called “red baths” contain iron. The transparent water nearest to the source produces the best effects.
| Characteristics | As the metal content in the water oxidizes when it comes into contact with the air, the water is yellow. |
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| Elements | Contains copper and iron. |
| Effects | General ailments such as neuralgia, muscle/joint pain, bruises, sprains sensitivity to cold relief from fatigue overall health promotion. |
In the same way as ferruginous onsen, there are carbonate types and sulphate types. The transparent water nearest to the source produces the best effects.
| Characteristics | Extremely good for the skin. |
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| Elements | The main element is aluminium. |
| Effects | Sterilizing effect, restores elasticity to the skin, chronic dermatitis, athlete’s foot, rashes, etc. Alunite onsen are particularly effective for ocular disorders. |
The formers names for this type of onsen were “alunite onsen” and “melanterite onsen” with alunite being aluminium sulphate and melanterite being iron sulphate.
| Characteristics | Highly stimulant, strong bactericidal effect. |
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| Elements | Contains high levels of isolated sulphates / chlorides, etc. , shows an acidic reaction (pH of 3or less). |
| Effects | Bactericidal effect, athlete’s foot and eczema, chronic dermatitis, etc. Removes old skin cell and stimulates the skin enhancing its natural healing power. |
Those with sensitive skin should avoid this type of onsen or should make sure they rinse thoroughly with fresh water after use.
| Characteristics | General purpose for all. |
|---|---|
| Elements | Alkaline water. Divided into sodium bicarbonate onsen and bicarbonate earth onsen. |
| Effects | (Sodium Bicarbonate Onsen) Bathing: Beauty effects making skin smooth, relief from fatigue, reinforces strength after illness, external wounds, dermatitis, etc. Drinking: Chronic gastritis, etc. (Bicarbonate Earth Onsen) Bathing: External wounds, dermatitis, atopic dermatitis, allergies, etc. Drinking: Gout, urate calculus, diabetes, etc. |
Although the properties of this water are such that everyone can use them, there are some cases in which slight irritation to sensitive areas of the skin may occur after bathing due to its strong alkaline nature. This is only a temporary effect but those with sensitive skin are advised to rinse with fresh water after using this type of onsen.
| Characteristics | Colourless and transparent. |
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| Elements | Water in which carbon dioxide is dissolved. |
| Effects | Bathing: Heart trouble, high blood pressure, etc. Drinking: Constipation and loss of appetite. |
Its former name is “Simple Carbon Dioxide Onsen”. Carbon dioxide stimulates respiratory and circulatory organs and has the effect of improving circulation by enlarging capillaries. As the effects listed above are obtained by lowering the oxygen partial pressure in the blood, those with respiratory or circulatory disorders risk further aggravation of symptoms due to over-stimulation if they do not exercise caution when bathing. Such patients who wish to bathe in a carbon dioxide onsen should discuss this with their doctor first. Further, even if permitted by a doctor, it is safer if these patients avoid spending a long time immersed in the water.
| Characteristics | Colourless and transparent water with the most beneficial effects. These are rare and therefore highly valued. |
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| Elements | Contains radioisotopes created by nuclear decay of tiny amounts of substances ranging from radium, radon and astatine to mercury. |
| Effects | Dermatosis, gynaecological disorders, external wounds, etc. Believed to be particularly effective on gout, lowering blood pressure and circulatory disorders. |
Onsen with a high content of radium are called “Radium Onsen”. The possibility of the radiation emitted having a harmful effect on the human body is low and as it activates immune cells by hormesis, it is actually considered to be good for the body. It also believed to have the possible effect of stunting the growth of cancer, but, at this point, there is no proven data for effects on any of these ailments and research results are awaited in the future.
| Characteristics | Bitter taste. If the onsen contains high levels of calcium sulphate, the water will feel slightly thick and smooth. |
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| Elements | Contains sulphate. |
| Effects | Bathing: Helps circulation, external wounds, gout, stiff shoulders, back pain, neuralgia, etc. Drinking: Constipation, rashes. |
Sulphates are highly effective on symptoms such as gout and neuralgia as they soften stiff areas (hardened skin) making them more supple. This is because calcium sulphate contains the elements of plaster. There is sometimes misunderstanding that these onsen contain sulphuric acid and are therefore dangerous; however, they actually contain harmless substances such as sodium sulphate and magnesium sulphate. Further, they do not give off the bad odour of hydrogen sulphide onsen. Sulphate onsen are safe onsen that are only harmful to those who are prohibited from bathing in them. The majority of commercial bath salts/powders have a similar composition to sulphate onsen.