Ethnopharmacological relevance: Indigo naturalis, a herbal medicine with a history of use dating back to ancient times, may be a good alternative topical treatment for atopic dermatitis (AD).
Aim of the study: To provide empirical evidence of the efficacy and safety of Indigo naturalis ointment in treating AD.
Materials and methods: In this randomized double-blind clinical trial, participants aged 6 to 65 years with AD affecting less than 40% of their body surface area (BSA) and an Investigator's Global Assessment (IGA) score of 2 to 4 were randomized (2:1) to receive either Lindioil ointment or a vehicle ointment twice daily for 6 weeks. The primary endpoint was the percentage change in the Eczema Area Severity Index (EASI) from baseline to week 6. Secondary endpoints were as follows: EASI improvement ≥50%, 75%, and 90%; IGA score; BSA affected by AD; pruritus severity; and Dermatology Life Quality Index. The safety assessment included adverse events (AEs), laboratory tests, and physical examinations.
Results: The Lindioil group (32 participants) and vehicle group (16 participants) achieved mean percentage EASI reductions of 49.9% ± 36.5% (95% CI 36.8%-63.1%) and 19.6% ± 52.2% (95% CI -8.2%-47.4%), respectively (P = 0.0235). The Lindioil group also showed greater improvement in every secondary assessment category. No significant AEs occurred.
Conclusion: Indigo naturalis ointment is effective for treating mild to severe AD topically, and appears to be safe. This is the first clinical trial to provide evidence supporting topical indigo-based AD treatment. ClinicalTrials.gov identifier: NCT02669888.
Keywords: Atopic dermatitis; EASI; Indigo naturalis; Indirubin.
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