Japan, due to its geological features and being a country made up of islands, is blessed with thousands of hot springs across the archipelago. Onsen is Japanese for hot spring. Technically, in Japan, a hot spring cannot be called an onsen unless it is over 25-degree Celsius that contains a defined level of natural mineral components. 

There are over 30,000 naturally occurring hot springs in Japan. Hot springs are formed by the heat and gasses of volcanic magma, wherein rainwater reaches the reservoir and comes in contact with volcanic gasses rich in minerals. It is said that the geothermal mechanisms that form a hot spring go through a 50-year process. This is the reason why they are believed to have special health benefits. You would not be able to soak in these minerals in your everyday bath. But what makes an onsen experience really special? The art of onsen is deep-rooted and has been practiced in centuries, with the first recorded onsen dating back to the year 712. The Japanese have turned the simple act of bathing into a fold tradition. And since its discovery, the healing properties of onsen has been widely recognized and considered to be one of the best ways for physical and mental relaxation.

With this abundance of Japanese hot springs, not all onsen are the same and each type is said to have its own therapeutic effects. Here’s a guide for spring water mineral composition with corresponding benefits for each kind that most likely will make you an onsen fanatic:

Simple Water (Tanjun-sen)

• Very mild stimulation for skin, recommended for children and those with sensitive skin
• Best for onsen beginners
• Good for insomnia and depression

Chloride Onsen ((Enka Butsusen)

• Good for cuts and burns, promote skin hydration and retains body heat

Carbonated Spring (Tansan-sen)

• improves circulation, for high blood pressure and rheumatism

Sulphate spring ((Ryusan-sen)

• good for healing cuts and bruise, low blood pressure

Carbon Dioxide Spring 

• good for cuts, low blood pressure, excessive sensitivity to cold

Iron or Ferruginous (Gantetsu-sen)

• for recovering iron levels, anemia and menstrual disorders

Antibacterial Acidic Water (Sansei-sen)

• Good for athlete’s foot and chronic skin diseases (not for people with sensitive skin)

Iodine-containing springs

• Good for Dyslipidemia

Sulfur (Iou-sen)

• Good for high blood pressure and joint pain, natural cures for acne and blemishes

Radioactive Spring (Hoshano-sen)

• Good for gout, high blood pressure, and rheumatism

I’M Hotel in Makati, houses the first Onsen Spa in the Philippines, which is also the largest urban spa in the country. I’M Onsen Spa features two onsen pools each with varying water properties. The state-of-the-art technology mimics the chemical composition of natural hot spring waters in Japan. Water types are rotating, featuring seasonal flavors, each with unique health and beauty benefits.