Warm "Hay Baths" for Osteoarthritis

Unusual European therapy shows promise for relieving pain related to osteoarthritis

By William Benda, MD

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Fioravanti A, Bellisai B, Iacoponi F, Manica P, Galeazzi M. Phytothermotherapy in osteoarthritis: a randomized controlled clinical trial. J Altern Complement Med.2011;17(5):407-412.


Randomized, controlled clinical trial


Osteoarthritis (OA) is the most common rheumatic disease in the developed world, increasing in frequency as the overall population increases in life expectancy. Pharmacologic therapies include analgesics, nonsteroidal anti-inflammatory drugs (NSAIDS), and selective COX-2 inhibitors, although these approaches are often plagued by adverse effects on the gastrointestinal tract, cartilage metabolism, and cardiac tissue. Current nonpharmacologic treatments such as heat and physical therapy have proven modest at best in treating pain and progressive disability.
In the Alpine area of Italy there is a long tradition of phytothermotherapy, or immersion of the patient’s body in fermenting freshly mown grass, to treat certain rheumatic diseases, including OA. Known as “hay baths,” this treatment consists of 20-minute daily immersions for 10 days in warm grass (50–58ºC).1 This treatment is used and studied especially in the area of Monte Bondone, a mountain above Trento, Italy.

Materials and Methods

218 outpatients (83 males, 135 females) afflicted by primary symptomatic OA of the lumbar spine (n=130), knee (n=44), or hip (n=44) were recruited by 2 general practitioners within 30 km of the spa center of Garniga Terme in Trento, Italy, between June 2007 and March 2008. All patients were symptomatic at the time of recruitment, and the diagnosis of OA was confirmed by American College of Rheumatology criteria and x-ray diagnosis.
The patients were randomized into 1 of 2 groups using a computer-generated table of random numbers. Group I (n=109) were given phytothermotherapy at the thermal center of Garniga Terme, while Group II (n=109) served as control, continuing regular outpatient care, including exercise, NSAIDs, and/or acetaminophen. Control individuals were also offered phytothermotherapy at the end of the study.
The grass was cut, gathered, and transported to the spa center according to traditional methods before it could dry.
Group I patients were submitted to once-per-day 20-minute immersions in a warm mixture of freshly mown hay for a total of 10 days. The grass was cut, gathered, and transported to the spa center according to traditional methods before it could dry. Once at the spa, 50 cm layers of hay were placed in the baths, where fermentation produced heat that reached a temperature of approximately 60ºC after 1–2 days. Group I patients were given daily immersions, with a 1-day rest after the fifth bath. Both treatment and control patients continued their usual pharmaceutical and nonpharmaceutical regimens, although no new therapies were introduced during the testing period.
All patients were assessed 3 times by a blinded physician: at baseline, at the end of the phytothermotherapy regimen 15 days later, and finally after 3 months. Metrics included a VAS scale of 0–100 for spontaneous pain, the Lequesne Index for severity of knee and hip OA,2 the Rolland Morris Questionnaire for the lumbar spine,3 and the Health Assessment Questionnaire.4,5 Drug consumption was recorded by the patients using personal diaries.


Only 1 patient in Group I was lost to follow-up after 15 days for personal reasons. At baseline there were no statistically significant differences in demographic and clinical variables between the 2 groups. Statistical analysis revealed significant improvements in the treatment group in all metrics tested at both 15 days and 3 months, while the control group did not demonstrate statistically significant improvement in any category. There was a significant decrease in NSAID, but not acetaminophen, use by the treatment group but not in the control group. With regard to adverse effects, 10% of the treatment group reported low-intensity disturbances that did not interrupt treatment, including asthenia, cutaneous reactions, post-bath tachycardia, and inflammation of the knee. In the control group 6% of patients complained of gastrointestinal side effects.


Although this therapeutic approach to OA may seem novel in our country, numerous studies have confirmed the benefits of phytothermotherapy in OA,6 fibromyalgia,7 lumbar pain,8 and ankylosing spondylitis.9 Although the mechanisms of action of phytothermotherapy are not known, they are likely related to exposure to increased temperature, although the influence of the active ingredients contained in the fermenting grasses (eg, essential oils, terpenes, other aromatic substances) may well contribute to the positive outcome of this study. Side effects appear to be minor and transient.

Practice implications

Although phytothermotherapy may appear at first blush to be an esoteric European technique, it is likely a close relative to hydrotherapy, mineral baths, and the application of warm essential oils prevalent within our complementary and alternative Western therapies. Even if soaking in a stew of chlorophyll and bacteria may not be an offering we can give to our own patients, demonstration of its effectiveness lends credence to those thermal approaches taught in our naturopathic and traditional Chinese medical schools.

About the Author

William Benda, MD, is a practicing emergency medicine physician, lecturer, writer, and researcher committed to the integration of alternative and conventional medicine. He is the first medical doctor to be elected to the Board of Directors of the American Association of Naturopathic Physicians and currently teaches at Southwest College of Naturopathic Medicine. His clinical work has focused on patients with breast cancer, animal-assisted therapy, and physician health and well-being; his research on equine-assisted therapy for children with cerebral palsy has been funded by the National Institutes of Health. He serves as Associate Editor of both the Journal of Alternative and Complementary Medicine and Integrative Medicine—A Clinician’s Journal.


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