Chinese Herbal Medicine Bath Therapy for Psoriasis Vulgaris: Current State of Evidence, a Pilot Randomised Controlled Trial and Patients’ Experience

<p dir="ltr">Background</p><p dir="ltr">Psoriasis vulgaris is the most prevalent type of psoriasis worldwide. Conventional therapies are commonly used to manage the disease, but they often provide inadequate long-term symptom relief, are expensive and can lead to undesirable side effects. For centuries, Chinese herbal medicine (CHM) has been widely used in China and other countries or regions to manage psoriasis. Although the American Academy of Dermatology Clinical Guidelines acknowledge CHM bath therapy as a potential treatment option for psoriasis, they refrain from making recommendations due to a lack of high-level clinical evidence. Systematic reviews reported favourable effects of CHM bath therapy for psoriasis vulgaris; however, they did not provide details regarding the ideal temperature and duration of CHM baths or overall treatment duration. Further, these reviews primarily focused on the add-on effects of combining CHM bath therapy with phototherapy, offering limited evidence on its clinical application as an adjunct to other conventional therapies.</p><p dir="ltr">The CHM formula fu zheng he fu zhi yang (FZHFZY) has been used as bath therapy for psoriasis for around 15 years at Guangdong Provincial Hospital of Chinese Medicine. Clinical observation indicated that it improves psoriasis lesion healing and reduces pruritus. Preclinical studies suggest the formula may possess antiangiogenetic activity, inhibit proliferation and improve epidermal differentiation to manage psoriasis. It may mitigate chronic pruritus in psoriasis by modulating caspase-14 protein expression. However, no rigorously designed randomised controlled trial (RCT) has been conducted to evaluate its efficacy and safety.</p><p dir="ltr">Feasibility and pilot studies are recommended in the early phase of developing and evaluating complex interventions. Insights gained from qualitative research may help explain the reasons behind pilot study findings, assess the relevance of the underlying theory and guide researchers towards more effective interventions for further investigation. Therefore, a mixed-methods feasibility study of FZHFZY bath therapy is warranted for patients with psoriasis vulgaris.</p><p dir="ltr">Aims, objectives and research questions</p><p dir="ltr">This project aimed to systematically evaluate the current state of clinical evidence on CHM bath therapy for psoriasis vulgaris and employ rigorous quantitative and qualitative research methodology to determine the feasibility and patient acceptability of conducting RCT using FZHFZY bath therapy for mild-to-moderate psoriasis vulgaris.</p><p dir="ltr">The specific objectives of this project were to:</p><p dir="ltr">• conduct systematic reviews of RCTs to evaluate the current state of evidence on CHM bath therapy for psoriasis vulgaris</p><p dir="ltr">• determine whether it was feasible to conduct a double-blinded RCT of FZHFZY bath therapy for mild-to-moderate psoriasis vulgaris</p><p dir="ltr">• gather patients’ experiences of participating in the pilot RCT and using bath therapy for psoriasis vulgaris management.</p><p dir="ltr">The research questions of this project were:</p><p dir="ltr">• What is the current evidence on CHM bath therapy for psoriasis vulgaris?</p><p dir="ltr">• Is it feasible to conduct an RCT of FZHFZY bath therapy for psoriasis vulgaris?</p><p dir="ltr">• What are the patients’ experiences of participating in the pilot RCT and using bath therapy to manage their psoriasis vulgaris?</p><p dir="ltr">Methods and results</p><p dir="ltr">Systematic reviews</p><p dir="ltr">Two systematic reviews of RCTs were conducted following the Cochrane Handbook for Systematic Reviews of Interventions version 6.4 to evaluate the current evidence on CHM bath therapy for psoriasis vulgaris. The first reviewed the effectiveness and safety of adding CHM bath therapy to conventional therapies for psoriasis vulgaris. The second undertook a systematic review and association rule analysis of CHM bath therapy for psoriasis vulgaris using calcipotriol (a first-line treatment) as the comparator. These systematic reviews revealed that CHM bath therapy was clinically beneficial and safe for adult patients when added to conventional treatments or directly compared with calcipotriol. There may be potential correlations between treatment effects and implementation factors, such as longer bath sessions (20–30 mins) for each session, increased bath temperature (≥ 38 °C) and extended course of treatment duration (eight weeks). The reviews also identified the high risk of bias associated with the included studies that may limit the generalisability of these findings. Both systematic reviews have been published.</p><p dir="ltr">Double-blinded pilot RCT</p><p dir="ltr">The double-blinded pilot RCT was a two-arm, randomised and placebo-controlled study. Sixty (60) eligible participants were randomly assigned (1:1) to receive either eight weeks of FZHFZY or placebo bath therapy plus 10% urea cream, with a 12-week post-intervention follow-up phase. FZHFZY trial preparation granules were subject to quality control including assays involving HPCL (high-performance liquid chromatography). The trial adhered to the Consolidated Standards of Reporting Trials extension to randomised pilot and feasibility trials, issued in 2016. In addition, preliminary data suggested potential clinical benefits and safety. The results demonstrated the feasibility of the trial protocol, as evidenced by high recruitment, retention and adherence rates, high satisfaction scores and a low rate of missed visits. The protocol of this pilot RCT, which includes an embedded qualitative study, has been published.</p><p dir="ltr">Embedded qualitative study</p><p dir="ltr">The qualitative study, embedded within the pilot RCT, involved 26 participants who completed the follow-up phase of the trial: 11 in the intervention group and 15 in the control group. Their experiences of participating in the trial and using bath therapy for managing psoriasis were explored through semi-structured interviews. Data were analysed using thematic analysis with an inductive approach and the study was reported following the Consolidated criteria for reporting qualitative research checklist. The findings indicated that the trial interventions were well-received by patients with psoriasis vulgaris. Participants’ motivations for engaging were mainly driven by cultural familiarity with Chinese medicine and personal experiences with psoriasis management. Patient satisfaction was largely shaped by whether the trial met their expectations for treatment outcomes. Most participants found the bath duration, treatment duration, and visit schedule appropriate, but their opinions on the bath frequency and lesion changes varied. Few participants followed the instructions on measuring bath temperature.</p><p dir="ltr">Conclusion</p><p dir="ltr">This project has evaluated the current clinical evidence on CHM bath therapy for psoriasis vulgaris through two systematic reviews that suggested the clinical benefit of CHM for psoriasis vulgaris. The feasibility and acceptability of adding CHM FZHFZY bath therapy to urea cream for patients with psoriasis vulgaris has been confirmed via a mixed-methods study. Further rigorous designed RCTs are warranted to generate additional new evidence of FZHFZY bath therapy for psoriasis vulgaris to support effective clinical decision-making.</p>