Tips & FAQ

General topics

In order to be officially recognized as an onsen the water has to fulfill certain criteria like the temperature of the water at the hot spring source that is fed from (at least 25°C) and the ratios of the mineral contents contained in the water. A sento is a public bath in which water is heated but not a hot spring.

Best time to avoid the crowds is around noon time and on working days. Weekends and evenings are busy.

Keep always a 100 Yen Coin with you as some Onsen’s locker room expect one (though there is an exchange machine “bill-to-coin”). You will get the 100 Yen back when you open your locker, so dont’' forget to take it.

In most onsen you cannot pay with credit card but only cash.

Most onsen allow 2h dwell time and 3h with sauna.

Go to the toilet before entering the Onsen bath facility as not every Onsen has a toilet inside which means you have to dry yourself and go through the changing room to the toilet.

Mix-gender is rare to find and it is more easy to find a facility which provides Hot Stone Sauna in which you wear cloth and lay down on a towel which allows mixed-gender.

Private bath. In Tokyo even private bath does not allow mix-gender. So better ask before you plan to have “couple time” together in a private bath.

The recommended bathing time for an onsen depends on the water temperature. In general be careful to not stay too long as you can get dizzy. If the hot spring water is 42°C do not stay longer than 5min. If the water has body temperature, around 36°C , you can soak for up to 40 minutes.

Japanese do normally not shave “down there” hence in case you do, you can encounter some glances. Just remember that all is forgotten when soaking in the bath.

As it is shared water, it is up to you if you prefer to shower again upon leaving the onsen. As the water has special benefits for the skin, most people do not shower. As some water could be harsh on your body and if you have sensitive skin it could be recommended to shower.

My standard itinerary (~1h)

From hot to cold. I start with the hottest bath and end with the cold bath.

After I washed myself thoroughly, I start with the Hot Bath (42+ °C), followed by a lower temperature bath (eg 38°C). Before entering the sauna, I go into the the Cold Bath (15-20°C).
Afterwards I relax outside on a chair or bench, followed by relaxing time in a bath with “body-temperature” water (36-38°C).

Afterwards I enter the Carbonate Bath and the Massage Jets Bath. To cool my body down, I enter the Cold Bath and proceed with the 2nd round of Sauna. Depending on the facility, time and mood, I do additional rounds.

Tip: focus on your breathing while relaxing in the 36-38°C water. Eg the 4-7-8 method. Breath through the noise in for 4 seconds, hold your breath for 7 seconds, and breath out for 8 seconds. Do this for 10min.

watch how others are behaving

In general the best is always to follow others and their behavior. E.g. when you sit outside on a stone bench, clean your seat first with water before sitting down (and clean, optional, when you get up and leave).

difference in Onsen water

Tanjun-sen (Simple water): Tanjun-sen is probably the most common type found in Japan. While they are called "Tanjun (simple)", it does not mean "the contents of the water are simple." We call all water where the mineral content does not reach a specific amount "simple". And even within the same typing there are many kinds. Since they don't have any special effects, the stimulation for the skin is very mild and good for a wide range of people, from babies to the elderly. I recommend people who take onsen for first time to take this type of water. A famous onsen with this Tanjun-sen water is Gero-onsen, in Gifu prefecture or Akanko-onsen, in Hokkaido.

Sansei-sen (Acidic water): Water which has a strong bacterial effect and is often used as a treatment is an acidic water called Sansei-sen.They works for healing scars, athlete's foot or chronic skin diseases. This water also works well making your skin more beautiful since the acid peels off old skin on the surface. This acidic water is made with a mixture of volcanic gas and ground water, and is said to be a very rare kind of water mostly found only in Japan. Since the effect and stimulation is very strong, there are some people who feel irritation on their skin. This onsen is not recommended for older people, sick people or people who have sensitive skin. Please make sure to wash all onsen water with fresh water after taking this acidic onsen and do not drink this water, otherwise your stomach will be hurt by the acid.

Alkaline water: Alkaline water is also called "Bijin-no-yu", which means Onsen of beautiful ladies. It is very popular, especially among ladies, because of its effect on beauty. This water feels thick and you can feel a silky smoothness on your skin straight away once you have taken this type of onsen. This alkaline water helps with melting sebum cutaneum, exfoliating the skin, making skin smooth and removing spots. For this reason it is called "Bijin-no-yu".

Iou-sen (Sulfer water): The most notable features of Iou-sen are definetly its smell (it is sulfuric, and so is commonly said to smell of rotten eggs) and the color of the water. The water changes its color into a milky white once exposed to the air. This onsen is easy to be recognized because of its unique smell and color. I imagine there are many people who do not like this type because of the smell, but the health effects of this water are superb. The gas which this water gives out works for clearing one's throat and is effective in helping with chronic bronchitis. They also make your blood vessels wider, and are effective for heart diseases, arteriosclerosis, or other skin diseases. Finally, they are used in drug addiction treatments because of its detoxification effects.

Gantetsu-sen (Iron water): We call water including iron Gantetsu-sen. The sourse of the water is clear in color, but it changes to a red/brown-ish color once exposed to oxygen because iron is oxidized. It smells like rust and tastes bitter. Since you can capture iron from taking the bath, it is good for anemia, and menopausal or menstruation disorders. It also warms your body quickly, so it is good for those with bad circulation. Since they have many positive effects work for women, this water is called Fujin-no-yu (Water of women) and is also popular as drinking water.

Tansan-sen (Carbonated water): This onsen water just looks like usual Tanju-sen, but once you take this onsen, many bubbles stick to your skin.This carbonated water improves your circulation, and is said to improve it three to five times more than fresh water. Because of the improvement of circulation, blood is delivered to all parts of your body. It works for removing waste from your body and detoxing. This tansan-sen is certified to have many unique effects good for your health by doctors, and often man-made carbonated water is used to heal diseases at the hospital or for making beautiful skin at Salons. But natural carbonated onsen water is very rare and is hard to find. Of those natural onsen, the one which is said to be the best is Nagayu onsen, in Ooita prefecture.

Difference in Onsen Baths & sauna

Kake-yu (掛け湯)

Usually the first thing you’ll see when you enter the bathing area. Yu (湯) means hot water and kake (かけ) means put on or throw—so this is the water that you dowse your body with before you enter the baths. Many opt to wash themselves in the showers instead, but in any case you should cleanse your body before you enter the baths.

Shower area

The bathtubs at the onsen and sento are not for cleaning your body; they are for relaxing and soothing the aches and weariness from a long day. You should cleanse yourself in the shower areas before entering the bathtubs. You will always find a line of showers (sometimes with separators, more often without) when you enter the bathing area. In front of the showers you will have a small basin (for shaving) and a stool. Japanese wash themselves while seated, although you do find standing shower cubicles in some onsen. Just about all onsen provide body wash, shampoo, and conditioner in the shower area.

Outdoor Bath - Rotenburo (露天風呂)

Literally, open-air bath, rotenburo are really what make bathing at the onsen in Japan so special. Most onsen will have a rotenburo, but there are views and then there are views.

Jet Bath

Same sort of thing as a Jacuzzi—bubbles fire up from different angles at your skin. Fairly common in the onsen, although less so at the more traditional establishments.

Carbonated Bath (二酸化炭素泉)

Ever wanted to bath in warm sparkling water? Well, now you can. The carbonated water is supposed to help with circulation, but the immediate effect is a tingling sensation on your skin.

Nekorobi (寝ころび)

Nekorobi are not baths as such; they are stone slabs over which warm onsen water trickles. You lie supine (usually with a raised stone for a pillow), and relax while looking up at the sky (the constant stream of water keeping your body from getting cold).

Hinoki Bath (檜)

Apanese cypress, hinoki cypress or just hinoki is a species of Cypress native to Japan. It is highly resistant to rot and is lemon-scented—the perfect wood from which to make a bathing tub.

Tsubo-yu (つぼ湯)

Tsubo-yu are often found at the onsen (usually outside). They are one-man pot tubs into which hot spring water constantly flows (and overflows). You can either squat down inside or, if you really want to show you’re an onsen lover, lie in with your arms and legs dangling out at the side.

Denki-buro【電気風呂】

This one is a bit more of a rarity. It’s a tub (or an area of a tub) which pulsates with an electrical current. Bathtubs and electricity are not normally two things that go hand-in-hand, but the denki-buro won’t give you a shock—it just produces an intermittent frizzling sensation on the skin like static electricity. If you’re interested, Yumori no Sato has an electric cave in its main open-air bath.

Scented Bathtub

This one is pretty obvious. Some onsen scent the water of bathtubs or put flowers, petals, and even fresh fruit into the water. Not seen so often, but they’re out there.

Silk Bath

A bit like a jet bath or Jacuzzi, but with very fine bubbles that turn the water white and feel like—you guessed it—silk on the skin.

Goemon Pot

A goemon pot is a type of wooden pot tub that gets its name from Ishikawa Goemon, an infamous outlaw in the Edo period who was boiled alive in one for his crimes.

Sauna

Not much explanation needed here, but the sauna at the onsen come in all different forms. The family-orientated onsen will often have televisions fitted with a tiered seating system so that everyone is facing the screen. The more traditional onsen will keep things simple and let you sweat in peace.

Steam Sauna

Dry saunas are typically 80-100°C with a humidity around 10%. Steam saunas, on the other hand, are set at a much lower temperature (around 40°C) but with a humidity closer to 100%. As a result they are less harsh than the typical dry saunas and more often found in the female onsen.

Mizuburo (水風呂)

If the onsen has a sauna, then it will almost always have a mizuburo (“cold water tub”). The temperature is usually around 17-20°C and you are supposed to get in after a stint in the sauna to cool the body down, but remember to wash away the sweat from your body in the shower area or by using the kake-yu before you do so.

Ganbanyoku (岩盤欲)

Called ganbanyoku (岩盤欲) in Japanese, Wikipedia tells me that this originated in Thailand, but in any case it is a popular beauty treatment service whereby users lie down on flat magma stones that are heated to 42-44°C. The heated stones apparently emit far-infrared rays which are supposed to help with metabolism and circulation, while the sweat emitted from your body has detox benefits. Although it is often termed “hot stone bathing” or “hot stone bath” in English, no water is used. Charges for this service are typically in addition to the entrance fee, but places like Heiwajima onsen have a hot stone room free as part of the baths.