鷹子温泉4号温泉Takanoko Onsen No. 4 Spring
Posted as the facility's newer source, Takanoko Onsen No. 4 Spring delivers gentle alkaline simple thermal water — lightly mineralized, easy on the body, and squarely in Japan's beauty-water family with its slippery, skin-smoothing alkaline feel. The posted notice lists chronic muscle and joint pain alongside the signature simple-spring indications of autonomic instability, insomnia and depressed mood. Because the source runs hot at the wellhead, the disclosure says the water is diluted to a comfortable bathing temperature and served with recirculation-filtration and chlorine-based disinfection, feeding the main bath, electric bath and walking bath.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
- Active stage of any illness (especially with fever)
- Active tuberculosis
- Advanced malignant tumor, severe anemia, or other cases of marked physical debilitation
- Severe heart or lung disease causing breathlessness on slight exertion
- Severe kidney disease accompanied by edema
- Gastrointestinal bleeding
- Visible bleeding
- Acute exacerbation of a chronic illness
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺163mgP42 national98%
- CalciumCa²⁺1.1mgP3 national0.7%
- LithiumLi⁺0.30mgP42 national0.6%
- AmmoniumNH₄⁺0.50mgP48 national0.4%
- PotassiumK⁺0.80mgP11 national0.3%
- AluminumAl³⁺0.20mgP64 national0.3%
- BariumBa²⁺< —mg
- CopperCu²⁺< —mg
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺< —mg
- Iron (III)Fe³⁺< —mg
- Magnesiummild; a laxative if you drink itMg²⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- StrontiumSr²⁺< —mg
- ZincZn²⁺< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻194mgP57 national46%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻95.7mgP39 national39%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻17.7mgP63 national9%
- Fluoridetrace; drinking limits applyF⁻7.5mgP86 national6%
- SulfateSO₄²⁻0.80mgP6 national0.3%
- Hydrogen sulfideHS⁻0.70mgP60 national0.3%
- HydroxideOH⁻0.20mgP66 national0.1%
- BromideBr⁻0.30mgP37 national0.0%
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- NitrateNO₃⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃42.8mgP23 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂10.1mgP56 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.30mgP13 national
- ArsenicAs< —mg
- CadmiumCd< —mg
- ChromiumCr< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- Chronic muscle or joint pain and stiffness (rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains — chronic phase)
- Cold sensitivity
- Peripheral circulation disorders
- Reduced gastrointestinal function (heaviness, bloating)
- Mild hypertension
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoid pain
- Stress-related symptoms (sleep disorders, depressed mood)
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.