Muddy hot springs are hot springs containing volcanic mud or mineral sediments, or baths where that mud is applied to the body for enjoyment. The water can look gray or brownish, and some tubs contain enough mud to scoop by hand, so first-time visitors often wonder, "Is it really okay to get in?"

In short, muddy hot springs are a special onsen experience common in volcanic areas, and the way you enjoy them varies widely by facility. Some places simply let you soak in mud-rich water, while others allow you to rub the mud from the bottom of the bath onto your skin. What matters in every case is not taking the mud out of the tub, following the on-site instructions, and being careful with your footing since the water is cloudy and the bottom is hard to see.

This article explains what muddy hot springs are, how they differ from regular onsen and milky-white baths, famous examples in Beppu and Akita, basic bathing methods and etiquette, and safety points. For how cloudy water in general turns white, see Why Milky White Hot Spring Water Turns Cloudy. For the full picture of the 10 spring types, see Guide to Hot Spring Water Types.

This article provides general information and does not guarantee any specific health or beauty benefits. Muddy hot springs can be hard to see into and slippery. If you have a chronic condition or are feeling unwell, do not overdo it and follow the facility's instructions.

What Are Muddy Hot Springs?

There are generally two types of what people call muddy hot springs.

The first is a hot spring that contains mud itself, formed by volcanic activity. In volcanic areas, high-temperature steam and gas rising from underground alter the surrounding rock and mix with deposits such as sulfur and iron sulfide, creating fine grayish-white mud. Bathing in water that contains this mud is what is commonly called a muddy hot spring or mineral-mud bath.

The second is a bath that includes a mud pack-style experience, where mud from the bottom of the tub or a separate container is applied to the skin. Depending on the facility, you may be able to do more than soak—you can also scoop up mud and spread it on your arms or legs.

However, even if a place is called a muddy hot spring, the water is not always literally mud-like. For example, Mudyū Onsen in Yuzawa, Akita, is said to have been named after the cloudy, muddy-looking water it once had, but today it has multiple springs and the water is not always scoopable mud. Do not judge by the name alone; check what the facility actually offers.

How It Differs from Regular Onsen and Milky-White Baths

The biggest difference between muddy hot springs and ordinary clear onsen is the appearance. The water is gray or brownish and it is hard to see the bottom or any steps. In addition, because mud clings to the body, you need to rinse it off well before getting out.

A similar-looking bath is the cloudy white "nigori-yu" or milky-white hot spring. In milky-white water, dissolved components precipitate as tiny particles and scatter light, making the water look white. Muddy hot springs, by contrast, contain larger mud-like deposits and can become thick enough to scoop by hand. That said, the two often exist on a continuum, and in volcanic hot spring areas milky-white baths and muddy hot springs are often found near each other. For the full mechanism behind cloudy water, see Why Milky White Hot Spring Water Turns Cloudy.

Representative Muddy Hot Springs

Japan's muddy hot springs are concentrated in volcanic areas. A few representative examples are listed below. Since conditions and usage vary by facility, check the latest information before visiting.

In Beppu, the Bozu Jigoku area itself is extremely hot—Oniishibozu Jigoku has a spring temperature of about 99°C—and is mainly a sight where gray hot mud bubbles up. Separately, Beppu also has rare bathing facilities where you can actually soak in gray mineral mud, and some operate under unique rules such as opening only in the morning. It helps to distinguish "jigoku = sightseeing" from "mineral-mud bath = bathing."

Goshogake Onsen in Hachimantai, Akita, is in a volcanic zone with fumaroles, mud pots, and large mud volcanoes, and is known for mud baths using sulfur-rich mineral mud. Meanwhile, Mudyū Onsen in Yuzawa, Akita, may be called "muddy hot spring," but as noted above, the current water is not always muddy. If you are looking for an actual muddy bath, compare options in the facility list.

How to Bathe and Etiquette

If it is your first time, the following steps are safe and considerate to others.

1. Read the facility signs and confirm whether the mud may be used on the skin
2. Wash your body first
3. Acclimate with a rinse and then soak briefly at first
4. Only if allowed, try a small amount on your arms or legs
5. Do not use it on the face or around the eyes or mouth unless instructed otherwise
6. Rinse the mud off thoroughly before getting out
7. Do not take mud out of the tub, onto towels, or into the changing room

You do not need to coat your whole body heavily from the start. Trying it little by little reduces both skin irritation and mess. Most important of all, do not carry mud outside the bath, onto towels, or into the changing room. Mud easily dirties shared spaces, and to keep muddy hot springs clean, it is essential to rinse off before entering and before leaving.

Safety Tips: Footing and Ventilation

Muddy hot springs have a few special cautions. First, the cloudy water makes the bottom hard to see. You may not be able to tell the depth of the tub, where the steps are, or how much mud has collected, so it is easy to slip. When entering or leaving, hold the edge or handrail and move slowly. Mud at the bottom is also slippery, so do not rush when standing up.

Second, volcanic muddy hot springs can contain sulfur, including hydrogen sulfide. If hydrogen sulfide accumulates in poorly ventilated places, it becomes a dangerous gas, and accidents have occurred in spring areas and fumarole zones. In fact, at Mudyū Onsen in Akita, there was a hydrogen sulfide poisoning accident in a nearby depression in 2005, which led to the creation of a restricted area. You do not need to worry excessively in normal bathing facilities, but if you start to feel stuffy, avoid long baths and always follow any restricted-area notices. For more on the smell, color, and gas behavior of sulfurous hot springs, see The Smell and Color of Sulfur Springs.

In strong mineral water, do not start with a long soak; try a short bath first. Older adults or people with chronic conditions should also check Precautions Before Entering a Hot Spring. Muddy hot springs are sometimes promoted as "beauty baths," but this article does not claim any effect. Instead, think of them as a unique way to enjoy the feel of the mud and the volcanic hot spring experience.

FAQ

What are muddy hot springs?

They are hot springs containing volcanic mud or mineral sediments, or baths where that mud is used on the skin for enjoyment. The water can look gray or brownish, and some tubs contain enough mud to scoop by hand. They are common in volcanic areas, and conditions and usage differ by facility.

Can I put the mud on my face?

It depends on the facility. Some places allow use on the face, while others do not. Since it can irritate the eyes or mouth, it is safer not to use it on your face unless specifically instructed. Always prioritize the on-site signs.

Do muddy hot springs help with beauty or skin care?

They are sometimes introduced as "beauty baths," but this article does not guarantee any benefit. It is better to enjoy them for the texture of the mud and the unique volcanic hot spring experience. If you have sensitive skin or any cuts or wounds, avoid using it, and stop immediately if it does not suit you.

Are there any things to watch out for in muddy hot springs?

Because the water is cloudy and the bottom is hard to see, move slowly when entering and leaving, and hold the handrail or edge. Do not take mud out of the tub, and rinse it off before getting out. In sulfurous baths, also be careful about stuffiness in poorly ventilated areas and about restricted-area signs in spring zones and depressions.

If a place is called "Muddy Hot Spring," does that mean I can definitely bathe in mud?

Not necessarily. Mudyū Onsen in Yuzawa, Akita, is said to have been named after its cloudy water in the past, but today it has multiple springs, and the mud may not always be scoopable. Do not judge by the name alone; check the facility's information.

Summary

Muddy hot springs are hot springs containing volcanic mud or mineral sediments, or baths where that mud is used on the skin for enjoyment. Representative examples include the Bozu Jigoku area and Myoban in Beppu, as well as Goshogake Onsen in Hachimantai, Akita. On the other hand, not every bath with "mud" in its name is literally muddy, and the experience varies by facility.

What travelers should remember is the etiquette of not taking mud out of the tub and rinsing it off before leaving, being careful with your footing because the cloudy water makes the bottom hard to see, and following ventilation rules and restricted-area signs in sulfurous volcanic baths. Rather than expecting too much in the way of beauty benefits, it is best to enjoy it as a special volcanic hot spring experience, starting with short sessions and without pushing yourself.

Sources

• Official Beppu Jigoku Meguri site, "Oniishibozu Jigoku"
• Wikipedia: Mudyū Onsen (Yuzawa, Akita, hydrogen sulfide gas accident)
• Wikipedia: Goshogake Onsen (Hachimantai, volcanic area and mineral mud)