Frequently Asked Questions

RootHerb® is an Eastern-born wellness concept that focuses on the “root” of herbs and spices grown underground and brings their components into daily life. A registered trademark advocated by the Japan Root Herb Association (JRHA), it organizes the “roots beneath the soil” long valued in traditional and folk medicine — in contrast to aroma-led green herbs (lemongrass, mint, etc.). Ginger, turmeric, galangal, and licorice are typical examples.

Ordinary herbs are mostly “green herbs” enjoyed for the aroma of leaves and flowers (lemongrass, mint, basil, etc.). RootHerb®, by contrast, focuses on the rhizome stored beneath the soil — ginger, turmeric, galangal, licorice and the like. The difference is which part is used, leaf and flower or root and rhizome; the latter has long been used in the traditional medicine and home cooking of Southeast Asia. The Japan Root Herb Association (JRHA) researches and raises awareness of this difference.

JRHA distinguishes herbs that have been used for their aroma from herbs that have been used through the root, and aims to introduce the culture of the latter in Japan. In the traditional medicine of Thailand and Southeast Asia, the rhizome is treated as a central material and appears across cooking, bathing and the herbal sauna. Together with the idea of “ichibutsu-zentai” (eating a food in its entirety brings good nutritional balance), JRHA works to spread knowledge of RootHerb®.

The herbal sauna is a traditional Thai bathing practice called “op samun phrai (อบสมุนไพร),” in which you bathe in the steam of medicinal herbs. Fresh herbs — lemongrass, kaffir lime, turmeric, galangal, pandan and more — are boiled in a large pot and their steam is fed into the sauna room. Studies of Thai traditional postpartum care report that the herbal steam bath has been understood as a way to warm the body, raise a sweat, and clear the skin and airways. The Japan Root Herb Association (JRHA) researches and educates about its culture and history.

Op samun phrai (อบสมุนไพร) is a term from Thai traditional medicine: “op” means to apply steam to the body, and “samun phrai” means medicinal herbs (poetically associated with the spirits of the forest). It roughly means “to bathe in the steam of the forest’s herbs.” It is the original name for the herbal sauna, used long before the Western word “sauna” reached Thailand, and deeply rooted in local life.

In Thai tradition, the herbal sauna (op samun phrai) has continued across the country as an extension of everyday bathing and as a postpartum custom. Under the four-element view of Thai traditional medicine (earth, water, wind, fire), childbirth is held to unsettle the fire element in particular, and the postpartum practice of yu fai (การอยู่ไฟ) is described as aiming to warm the body back into balance. The herbal steam bath is one part of it, reported as having been understood as a way to warm the body, raise a sweat, and clear the skin and airways. The blend of herbs differs by region and by venue, and the recipes are handed down. The Japan Root Herb Association (JRHA) presents it not as a medical practice but as “time to open the senses and meet your own body,” to bring into modern life.

Where Finnish saunas and Japanese steam saunas center on “heat and humidity,” the Thai herbal sauna (op samun phrai) makes “herbal steam” the star. Fresh herbs are boiled in a large pot and you bathe in that steam, so the room fills with their aroma. Each facility differs in its herb blend and steam method (wood-fired / gas / industrial), and each is tied to its local culture.

The Japan Root Herb Association (JRHA) runs the “Thai Herbal Sauna Tour” once a year — an on-site herb school and facility study programme in Phuket and Bangkok. The third edition runs Oct 31 – Nov 5, 2026 (4 nights, 6 days), limited to 8 people on a first-come basis, at about ¥168,000. It covers visits to five Phuket facilities, history and knowledge in Bangkok, and — for those who wish — earning the local Root Herbalist certification. It starts and ends locally in Thailand; flights and overseas travel insurance are arranged by each participant. Apply via the form on this site (/apply-tour).

Thai Root Herbalist is a one-of-a-kind specialist certification in Thai RootHerbs, earned through a one-day intensive course and exam led by local instructors. Only participants of the JRHA-organized Thai Herbal Sauna Tour (the on-site training programme) may take it. The basic course has three parts: (1) history of the Thai herbal sauna, (2) Thai RootHerb theory, and (3) Thai RootHerb practice. It is a practical credential for running a herbal sauna at a salon, spa, or treatment studio.

Newcomers are very welcome. It suits anyone curious about Thai traditional medicine or about plants and the culture around them, those who want to learn customs rooted in a place, and those who want to study deeply while taking in the atmosphere on the ground. The coordinators (Koichi Suzuki, Nana Uchida, Satoshi Ryuto) support the whole itinerary on site. As a small-group programme by the Japan Root Herb Association (JRHA), it answers individual questions with care.

Typical herbs in the Thai herbal sauna (op samun phrai) include turmeric (kamin ขมิ้น), galangal (kha ข่า), lemongrass (takhrai ตะไคร้), the kaffir lime fruit and leaf (makrut มะกรูด / bai makrut ใบมะกรูด), pandan leaf (bai toey ใบเตย), and tamarind leaf (bai makham ใบมะขาม). The Japan Root Herb Association (JRHA) systematically researches and shares their species, origins, and how they are used.

Turmeric (Thai: kamin ขมิ้น; Curcuma longa) is a rhizome in the ginger family and a RootHerb® indispensable to both Thai traditional medicine and Thai cooking. It contains the vivid orange pigment curcumin, and is marked by an earthy aroma with a faint bitterness. It has been used widely — in cooking, the herbal sauna, topical preparations, and herbal teas. Thai folk practice is recorded as applying it to the skin as a body mask, and as turning to it for stomach upsets, skin troubles, coughs and aching joints. The Japan Root Herb Association (JRHA) introduces turmeric as “a herb that helps like a forest spirit.”

Galangal (Thai: kha ข่า; Alpinia galanga) is a perennial in the ginger family and a relative of ginger, but a RootHerb® with a sharper, more citrus-like aroma. Its scent underpins tom yum goong and much of Thai cooking, and it is one of the herbal sauna’s key herbs. In Thailand it is reported as having been treated as a carminative for digestive complaints such as bloating. The Japan Root Herb Association (JRHA) introduces galangal’s own aroma and uses, distinct from ginger.

Lemongrass (Thai: takhrai ตะไคร้; Cymbopogon citratus) is a perennial grass marked by a fresh, lemon-like aroma. In Thailand it has been used across daily life — in cooking (tom yum), in herbal teas, and in the herbal sauna. It is also recorded as a mosquito repellent and as a herb turned to in fever and pain, and the citral that makes up around 80% of its essential oil is traditionally described as a calming scent. In the Thai luk prakop compress, a formulation recorded in the peer-reviewed literature includes its leaves and sheaths at about 10%. On the Japan Root Herb Association (JRHA) on-site training, it is experienced as fresh-lemongrass steam at facilities in Phuket.

Individual membership dues are ¥5,000 a year (supporting members ¥30,000). After applying via the dedicated form and transferring the dues to SBI Sumishin Net Bank, a membership number is issued. Members receive (1) the members’ newsletter, (2) admission to events at member rates, and (3) other member services. Membership is open to licensed medical and care professionals, researchers and students in related fields, and interested members of the public.

The Japan Root Herb Association (JRHA) is a general incorporated association founded in May 2024, headquartered in Tokyo, corporate number 5011105011042. It studies and introduces the Thai steam bath tradition known as the herbal sauna (op samun phrai), and the root herbs — RootHerb® — at the centre of it. Activities: research, certification, training RootHerb instructors, seminars and workshops, exchange with overseas bodies, and cultivation on its own and partner farms. Representative director: Satoshi Ryuto; directors: Nana Uchida and Koichi Suzuki.

The Japan Root Herb Association (JRHA), headquartered in Tokyo, was founded in May 2024; its corporate number is 5011105011042. Its representative director is Satoshi Ryuto; directors are Nana Uchida and Koichi Suzuki; and its special advisor is Tadateru Isono (head of the Thailand Samun Phrai Project). Its partner is the Thai Herbal Massage School, Bangkok. It shares its activities on Instagram at @jrha_official.

Five facilities the Japan Root Herb Association (JRHA) visited in November 2024: (1) Kathu Herb Sauna (a paradise deep in the jungle), (2) TIRA Herbal Sauna & Spa (a refined space full of the owner’s heart), (3) Ao-Chalong Sauna (a wood-fired steam purist), (4) ILAND Herbal Spa (a resort-style luxury sauna), and (5) Kao Lan Sauna (a local public sauna with an air reminiscent of Helsinki’s oldest). See JRHA’s Field Notes for details on each.

Phuket is one of Thailand’s leading areas where, in the dry season (October–March) when fresh herbs are at their peak, a wide range of herbal-sauna facilities — from luxury to local — gather. Each differs in its steam method (wood-fired / gas / industrial) and in the blend and origin of its herbs. The Japan Root Herb Association (JRHA) holds on-site training in Phuket each year, offering a rare chance to learn systematically, right down to behind the scenes.

The Japan Root Herb Association (JRHA) suggests bringing RootHerb® into daily life by (1) cooking — ginger, turmeric, galangal in stews and stir-fries; (2) herbal tea — simmering the roots; (3) herbal bath — herbs as a bath additive; and (4) aroma — dried roots for scent. The key is “ichibutsu-zentai” (eating a food in its entirety): using the whole root, skin and fibre included.