Topical Arnica tincture as a promising therapeutic alternative for cutaneous Leishmaniasis: Evidence from a phase Ib/II clinical trial

Cutaneous leishmaniasis (CL) is caused by various species of Leishmania parasites. It has a global incidence of 1.2 million cases annually, primarily in the Americas and the Eastern Mediterranean region. Despite the continued use of pentavalent antimonials as the standard treatment, their toxicity has prompted the search for alternative therapies [ 1 ]. Arnica montana L. (Asteraceae) is widely recognized as a phytotherapeutic plant due to its anti-bruising, analgesic and antimicrobial properties. The tincture obtained from the flowers has demonstrated excellent in vivo activity against CL in a hamster model [ 2 ] and high skin permeability and retention in the epidermis without systemic circulation, making it a promising option for topical treatments [ 3 ]. A phase Ib/II clinical study (NCT05094908) was conducted to evaluate the safety, tolerance, and therapeutic response of arnica tincture in patients with CL [4]. Sixteen participants aged 18 to 65 years, all diagnosed with CL, were randomly assigned to receive Arnica tincture, applied topically three times daily for either 30 or 45 days. Of the 12 participants who completed the 180-day follow-up, all achieved complete lesion healing, demonstrating a 100% cure rate ([ Fig. 1 ]). The remaining four participants withdrew their informed consent before or during treatment. The most common adverse events were mild and included erythema, pain, edema, and a burning sensation at the application site. No severe adverse effects were reported. Fig. 1 Appearance of CL of a representative participant treated with arnica tincture for 30 days. TD0: Before treatment; D30: last day of treatment; PTD45: day 45 after end of treatment; PTD90: day 90 after end of treatment and PTD180: day 180 after end of treatment Arnica tincture demonstrated promising results in treating CL and exhibited a favorable safety profile. However, due to the small sample size and absence of comparison with conventional therapies, a further phase III study with more robust methodological design has been initiated to assess its efficacy accurately. Funding: This research was funded by the Wilhelm Doerenkamp-Foundation, grant specification: NATVANTAGE RESEARCH GRANT 2018. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany