Clinical effects of Kneipp hydrotherapy: a systematic review

This systematic review evaluated all available randomized controlled trials (RCTs) investigating the clinical effects of hydrotherapy according to Kneipp which is characterized by cold water applications. All RCTs on therapy and prevention with Kneipp hydrotherapy were included. Study participants were patients and healthy volunteers of all age groups. MEDLINE (via PubMed), Scopus, Central, CAMbase, and opengrey.eu were systematically searched through April 2021 without language restrictions and updated by searching PubMed until April 6th 2023. The risk of bias was assessed using the Cochrane tool version 1.

Twenty RCTs (N=4247) were included. Due to the high heterogeneity of the RCTs, no meta-analysis was performed. The risk of bias was rated as unclear in most of the domains. Of 132 comparisons, 46 showed significant positive effects in favor of hydrotherapy on chronic venous insufficiency, menopausal symptoms, fever, cognition, emotional function, and sickness absenteeism. However, 81 comparisons showed no differences between groups, and 5 were in favor of the respective control group. Only half of the studies reported safety issues.

The authors concluded that although RCTs on Kneipp hydrotherapy seem to show positive effects in some conditions and outcomes, it remains difficult to ascertain treatment effects due to the high risk of bias and heterogeneity of most of the considered studies. Further high-quality RCTs on Kneipp hydrotherapy are urgently warranted.

This is certainly the best review of the subject so far. It makes it very clear that the evidence for Kneipp hydrotherapy is weak, mostly because of the many flaws in the primary studies. One needs to add, I think, that 20 RCTs are an absurdly small amount considering that many indications this type of therapy is advocated for – many enthusiasts even consider it a panacea.

It follows, I fear, that Kneipp hydrotherapy is almost entirely not evidence-based. This should be bad news for the numerous institutions and Spa towns (mostly in Germany) that live on employing this treatment and telling patients that it is effective. They usually claim that experience shows this to be true. But this was the mantra of medicine ~100 years ago. Since then, we have learned that experience is a very poor guide that regularly leads us up the garden path.

Kneippians will counter that clinical trials are difficult to conduct and expensive to finance. Both arguments are of course true but, considering that an entire industry lives on telling patients something that essentially amounts to a lie (i.e. the claim that it works), it surely is obligatory to overcome these obstacles.