"Ah, the smell of an onsen!" As you approach a hot spring town, a unique scent hits your nose. It resembles the smell of rotten eggs. This is the scent of sulfur. This aroma is what gives you the strongest sense of "I've arrived at an onsen!"

What is the Sulfur Scent?

The sulfur scent refers to the smell of hydrogen sulfide gas emanating from sulfur springs. It is often described as "the smell of rotten eggs" or "the onsen smell."

Even before entering the hot spring, this scent pervades the air. The entire hot spring town is enveloped in this distinctive aroma.

Why Does It Smell Like Sulfur?

The true cause of the sulfur scent is hydrogen sulfide gas.

Due to volcanic activity, underground sulfur dissolves into the hot spring water. This sulfur undergoes a chemical reaction, producing hydrogen sulfide gas. This gas creates the "rotten egg smell."

Hydrogen sulfide has a very strong odor. Even in small amounts, it is clearly detectable.

Types of Hot Springs with Sulfur Scent

Hot springs with a sulfur scent are primarily sulfur springs.

Hydrogen Sulfide Type Sulfur Springs: Contains a lot of hydrogen sulfide gas. Has the strongest sulfur scent.

Sulfur Type Sulfur Springs: Contains a lot of sulfur but less hydrogen sulfide. The scent is relatively weak.

Additionally, acidic springs and sulfate springs may also have a sulfur scent.

Representative Hot Springs with Sulfur Scent

Kusatsu Onsen (Gunma Prefecture): One of Japan's three famous hot springs. Known for its strong sulfur scent.

Noboribetsu Onsen (Hokkaido): The sulfur scent rising from Hell Valley is impressive.

Owakudani in Hakone Onsen (Kanagawa Prefecture): Due to volcanic activity, a strong sulfur scent permeates the area.

Unzen Onsen (Nagasaki Prefecture): Known for its "hell tours," the area is filled with the scent of sulfur.

The Charm of the Sulfur Scent

The sulfur scent is polarizing; some love it, others don't. However, many onsen enthusiasts adore this aroma.

The Feeling of "I've Arrived at an Onsen": The sulfur scent evokes a strong sense of "I've arrived at an onsen!" It enhances the feeling of being away from everyday life.

Proof of a Genuine Onsen: The presence of a sulfur scent = volcanic hot spring = genuine onsen, is a common association.

Nostalgia: The sulfur scent often brings back memories of onsen trips. Many find it nostalgic.

Expectation of Health Benefits: Sulfur-scented hot springs are often believed to have high therapeutic benefits.

For Those Who Dislike the Sulfur Scent

Some people dislike the sulfur scent. This is perfectly fine.

There are many hot springs without a sulfur scent. Simple springs, chloride springs, and bicarbonate springs are often odorless or have a faint smell.

Sulfur-scented hot springs are not the only "genuine" ones. Odorless hot springs also have excellent benefits. Choose a hot spring that suits your preferences.

Getting Used to the Sulfur Scent

Initially, the sulfur scent may seem overwhelming. However, you get used to it over time.

After soaking in the onsen for about 10 minutes, you may stop noticing the scent. This is because your sense of smell adapts.

Even if you dislike the sulfur scent, give it a try. You might find yourself getting used to it.

The Sulfur Scent and Health Benefits

In small amounts, hydrogen sulfide may have positive health effects.

It can dilate blood vessels and promote circulation. It is also said to have antioxidant properties.

However, high concentrations of hydrogen sulfide are toxic. Onsen facilities are properly ventilated, so there is no concern for health risks.

The Strength of the Sulfur Scent

The strength of the sulfur scent varies by hot spring.

Some hot springs, like Kusatsu Onsen and Tamagawa Onsen, have a very strong scent. Others have only a faint sulfur aroma.

Hot springs with a strong sulfur scent tend to have concentrated components. However, "strong scent = high efficacy" is not always true.

Enjoying the Sulfur Scent

The sulfur scent is an olfactory onsen experience.

Close your eyes and take a deep breath. Smell the sulfur aroma. Savor the feeling of "I've arrived at an onsen." Completely detach from everyday life.

The sulfur scent is a crucial element for enjoying the onsen experience with all five senses.

Conclusion

Sulfur-scented hot springs are a symbol of Japan's volcanic onsen. The unique aroma of rotten eggs gives the strongest sense of "I've arrived at an onsen!"

Hydrogen sulfide gas is the true cause of this scent. While opinions vary, many onsen enthusiasts love this aroma.

The sulfur scent is an olfactory onsen experience. Enjoy the unique aroma of Japan's volcanic hot springs.