Onsen: Benefits of Alkaline and Acidic Hot Springs

Have you ever heard that in Japan there are five types of “Onsen (温泉)” hot springs that were defined based on pH values by Japan’s Ministry of Environment?

For those who don’t know about this, first of all, they are as follows.

pH values Types of Onsen
pH8.5 or above Alkaline Onsen
pH7.5 to pH8.5 Weak Alkaline Onsen
pH6.0 to pH7.5 Neutral Onsen
pH3.0 to pH6.0 Weak Acidic Onsen
pH2.0 to pH3.0 Acidic Onsen

Benefits of Alkaline and Acidic Onsen 

Each Onsen listed above has its own characteristic properties, but today I will just talk about the difference in benefits between alkaline and acidic hot springs.

Now, let’s get started with Alkaline Onsen.

Alkaline Onsen (pH7.5 or above)

Alkaline Onsen

In addition to dissolving sebum on the surface of the skin, alkaline hot spring water softens keratin so it can smoothen skin texture.

For that reason, many alkaline Onsen hot springs in Japan are called “Bijin no Yu (美人の湯)” loosely meaning “Hot spring for making you more beautiful”

However, if the pH value of an alkaline hot spring is quite high, that can cause dryness of the skin.

Therefore, after you soak in a strong alkaline Onsen bath, it is better to have a shower in order to wash away components from the hot spring water.

Acidic Onsen (pH2.0 to pH6.0)

Tamagawa Onsen (玉川温泉)Tamagawa Onsen

On the other hand, Onsen with low pH values has strong sterilizing power so it may give your skin some tingling sensation. But the acidic water is especially effective for chronic skin diseases such as athlete’s foot.

However, soaking in a quite strong acidic Onsen bath can cause rough skin. Therefore, as with the case of Alkaline Onsen, after bathing, it is better for you to have a shower in order to remove its components from your body.

By the way, speaking of acidic Onsen, Tamagawa Onsen, a hot spring resort in Akita Prefecture, is especially famous.

(Reference Page: tenseien.co.jp)


Hi, I'm Tomo, a Japanese blogger living in Niigata Prefecture, Japan. For the purpose of enriching your life, I would like to introduce things about Japan on this blog, especially unique Japanese products, cooking recipes, cultures, and facts and trivia.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: