Clinical efficacy and IL-17 targeting mechanism of Indigo naturalis as a topical agent in moderate psoriasis.
Cheng HM, Wu YC, Wang Q, et al. Clinical efficacy and IL-17 targeting mechanism of Indigo naturalis as a topical agent in moderate psoriasis. BMC Complement Altern Med 2017;17(1):439.
Study type: RCT + gene-expression profiling (Janssen R&D collaboration; NCT01901705) · Added to this library August 23, 2026
What the researchers did
A pharma-collaborated trial that sequenced patients' skin before and after indigo treatment.
What they found
PASI75 in 56% vs 0% on placebo; the IL-17 inflammatory gene signature was normalised by treatment; the active tryptanthrin directly inhibited IL-17 signalling in skin cells.
Why it matters
IL-17 is the axis behind the thick, sharply-bordered "psoriasiform" eczema common in Asian skin — this is why the Blood-Heat plaque is indigo's lesion.
Relates to the patterns: Blood Heat · Heat-Toxin
This summary is educational and does not replace care from your child's pediatrician. Evidence tiers matter: a finding in cells or animals is a reason a treatment could work, not proof that it does.
More in Qing Dai Gao
Efficacy and safety of indigo naturalis ointment in Treating Atopic Dermatitis: A randomized clinical trial.
Lin YK, Chang SH, Yang CY, See LC, Lee BH, Shih IH. Efficacy and safety of indigo naturalis ointment in Treating Atopic Dermatitis: A randomized clinical trial. J Ethnopharmacol 2020;250:112477.
Study type: RCT (double-blind, vehicle-controlled; ages 6–65; NCT02669888)
What: Refined indigo naturalis oil (Lindioil) twice daily vs vehicle for 6 weeks in 48 people with atopic dermatitis, including children from age 6.
Found: Eczema severity (EASI) fell 49.9% on indigo vs 19.6% on vehicle (p=0.024); superior on every secondary endpoint including itch and quality of life; no significant adverse events.
Why it matters: The first randomized trial of a topical Qing Dai preparation in eczema itself — the "clear Heat, cool Blood" ointment beat its own base oil, with pediatric participants included.
Efficacy and safety of indigo naturalis oil extract (Lindioil ointment) for the treatment of atopic dermatitis: a randomized, crossover, evaluator-blinded, controlled trial.
Yang CY, et al. Efficacy and safety of indigo naturalis oil extract (Lindioil ointment) for the treatment of atopic dermatitis: a randomized, crossover, evaluator-blinded, controlled trial. Front Pharmacol 2025;16:1546589.
Study type: RCT (crossover vs tacrolimus, n=22 adults)
What: Indigo ointment head-to-head against tacrolimus, a standard prescription immunosuppressant cream.
Found: Tacrolimus reduced severity more (−71% vs −41% EASI), but caused local side-effects in 61% of users vs 10% for indigo; indigo also reduced S. aureus colonisation toward healthy-skin levels and shifted the skin microbiome back toward normal.
Why it matters: Honest comparison: the pharmaceutical is stronger, the herb is far gentler — and only the herb showed the antimicrobial, microbiome-restoring action. Different tools for different lesions.
Comparison of indirubin concentrations in indigo naturalis ointment for psoriasis treatment: a randomized, double-blind, dosage-controlled trial.
Lin YK, et al. Comparison of indirubin concentrations in indigo naturalis ointment for psoriasis treatment: a randomized, double-blind, dosage-controlled trial. Br J Dermatol 2018;178(1):124-131.
Study type: RCT (dose-ranging)
What: Four concentrations of indirubin (indigo's key active) in psoriasis, to find the dose-response.
Found: Highest dose: PASI severity down 69%, with 57% of patients reaching PASI75 and 30% PASI90; no severe adverse events over 20 weeks.
Why it matters: A clean dose-response curve is pharmacology's signature that the active is real — indirubin behaves like a drug because it is one.
Clinical assessment of patients with recalcitrant psoriasis in a randomized, observer-blind, vehicle-controlled trial using indigo naturalis.
Lin YK, et al. Clinical assessment of patients with recalcitrant psoriasis in a randomized, observer-blind, vehicle-controlled trial using indigo naturalis. Arch Dermatol 2008;144(11):1457-64.
Study type: RCT (intra-patient, vehicle-controlled, n=42)
What: Crude indigo ointment vs its own base, on matched plaques of the same patients, 12 weeks.
Found: 74% of patients reached clearance or near-clearance on the treated side; severity scores halved relative to control.
Why it matters: Published in the American Medical Association's dermatology journal — the moment topical Qing Dai entered the Western evidence base.