Indigo naturalis, also known as Qing dai, is an herb commonly used in traditional Chinese medicine. It is extracted from the leaves of specific plants including, Indigofera tinctoria, baphieacanthuscusia, Isatis tinctoria, Polygonum tinctorium, and Isatis indigotica. These plants have indigo within their leaves, giving the plant a natural blue color. Although indigo naturalis has been used for centuries in traditional Chinese medicine, Western medicine has only recently focused on using the herb for medical conditions. Research on the uses of indigo naturalis has exploded over the last few decades and continues to develop.
Psoriasis is one of the conditions indigo naturalis has been shown to treat. The topical application of the herb is the most effective route for skin conditions, although there are oral forms used for conditions like ulcerative colitis. Psoriasis is a common inflammatory and chronic skin condition that requires daily use of topical treatments with various side effects. An alternative topical therapy that is safe and effective with fewer side effects may assist many patients that have not found the best disease control with currently available therapies.
A Natural Way to Combat Inflammation
Psoriasis occurs with inflammation of the skin, which triggers a cascade of different events leading to plaques on the skin. Indigo naturalis combats several events in the development of psoriasis lesions, also known as plaques. What makes indigo naturalis so effective? There are 3 major components of indigo naturalis: indigo, indirubin, and tryptanthrin.
Indigo is the compound that gives the herb its color. Indigo naturalis in its natural form is a blue powder. This makes the compound a great dye for clothing and other products, but if the color remains in its natural form, indigo naturalis can stain the skin. For this reason, the herb usually undergoes further processing to avoid this effect.
Indirubin affects the increased number of skin cells proliferating at one time in psoriasis. A molecule in cells known as CDC25B and a molecule that signals cells to proliferate known as EGFR both play an important role in the increased skin cell numbers. Indirubin has been found to decrease the amount of CDC25B in the cell and stop EGFR activation. This leads to a decrease in the skin cell turnover, which combats psoriasis plaque formation.
Tryptanthrin decreases IL-17, an important signaling molecule that promotes inflammation and is known to be increased in psoriasis.
Indigo naturalis as a whole herb improves skin cell connections, which are very important for normal skin function. The connections are often disrupted in psoriasis. These tight connections between cells include a protein called claudin-1. Indigo naturalis improves the skin cell connections by increasing the amount of claudin-1. Additionally, the herb has been shown to decrease the inflammation associated with a special cell called neutrophils. Neutrophils are a major cell type involved in psoriasis development. Interestingly, the individual components of indigo naturalis are not effective alone. This tells us indigo, indirubin, and tryptanthrin within indigo naturalis must work together to exert their effects.[5,6]
Does Indigo Naturalis Work?
One study compared the common topical vitamin D agent, calcipotriol, to a topical form of indigo naturalis called Lindioil. Lindioil is the product of olive oil and indigo naturalis extract. The oil makes indigo naturalis easier to apply and the extract attempts to remove a lot of the blue color in the herb to avoid staining of the skin and nails. The results showed that after use for 24 weeks Lindioil significantly improved nail psoriasis. More importantly, the study showed that only 6% of people experienced irritation with indigo naturalis compared to 30% using calcipotriol and 82% of people preferred Lindioil over the calcipotriol.
Another study looked into the most effective dosage of the active ingredient, indirubin, in topical Lindioil for psoriasis of the skin and whether the topical therapy was safe in all concentrations. The researchers changed the amount of indirubin in the Lindioil to test the different concentrations of indirubin alongside the other active ingredients in indigo naturalis. Lindioil was effective for psoriasis and the greatest concentration of the indirubin (200 μg/g) in the Lindioil was the most effective for treating psoriasis. Over the 20 weeks of the study, there were very few adverse reactions, most of which consisted of mild redness in patients with multiple allergies.
Indigo Naturalis for Nail Psoriasis
The early research suggests that indigo naturalis may work for skin psoriasis, but additional studies have also shown that it works with difficult-to-treat nail psoriasis. Over 24 weeks in 2 separate studies, Lindioil was shown to be safe and effective in treating nail psoriasis.[7,9,10] A case of a pediatric patient with nail psoriasis that had responded for only short periods of time to topical steroids and urea was treated successfully with topical indigo naturalis. Additional cases of successful nail psoriasis treatment with indigo naturalis oil extract have been documented. Nail psoriasis often has few effective therapeutic alternatives so giving patients another topical option for their nail psoriasis would help many patients find nail resolution.
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McDermott L, Madan R, Rupani R, et al. A Review of Indigo Naturalis as an Alternative Treatment for Nail Psoriasis. J Drugs Dermatol.2016;15(3):319-323; PMID: 26954317 Link to research.
Suzuki H, Kaneko T, Mizokami Y, et al. Therapeutic efficacy of the Qing Dai in patients with intractable ulcerative colitis. World J Gastroenterol.2013;19(17):2718-2722; PMID: 23674882 Link to research.
Hsieh WL, Lin YK, Tsai CN, et al. Indirubin, an acting component of indigo naturalis, inhibits EGFR activation and EGF-induced CDC25B gene expression in epidermal keratinocytes. J Dermatol Sci.2012;67(2):140-146; PMID: 22721997 Link to research.
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; PMID: 28865459 Link to research.
Lin YK, Chen HW, Leu YL, et al. Indigo naturalis upregulates claudin-1 expression in human keratinocytes and psoriatic lesions. J Ethnopharmacol.2013;145(2):614-620; PMID: 23220199 Link to research.
Lin YK, Leu YL, Huang TH, et al. Anti-inflammatory effects of the extract of indigo naturalis in human neutrophils. J Ethnopharmacol.2009;125(1):51-58; PMID: 19559779 Link to research.
Lin YK, Chang YC, Hui RC, et al. A Chinese Herb, Indigo Naturalis, Extracted in Oil (Lindioil) Used Topically to Treat Psoriatic Nails: A Randomized Clinical Trial. JAMA Dermatol.2015;151(6):672-674; PMID: 25738921 Link to research.
Lin YK, See LC, Huang YH, et al. Comparison of indirubin concentrations in indigo naturalis ointment for psoriasis treatment: a randomized, double-blind, dosage-controlled trial. Br J Dermatol.2017;10.1111/bjd.15894PMID: 28815560 Link to research.
Lin YK, See LC, Huang YH, et al. Efficacy and safety of Indigo naturalis extract in oil (Lindioil) in treating nail psoriasis: a randomized, observer-blind, vehicle-controlled trial. Phytomedicine.2014;21(7):1015-1020; PMID: 24680615 Link to research.
Lin YK, See LC, Chang YC, et al. Treatment of psoriatic nails with indigo naturalis oil extract: a non-controlled pilot study. Dermatology.2011;223(3):239-243; PMID: 22056841 Link to research.
Liang CY, Lin TY, Lin YK. Successful treatment of pediatric nail psoriasis with periodic pustular eruption using topical indigo naturalis oil extract. Pediatr Dermatol.2013;30(1):117-119; PMID: 22471655 Link to research.
Lin YK. Indigo naturalis oil extract drops in the treatment of moderate to severe nail psoriasis: a small case series. Arch Dermatol.2011;147(5):627-629; PMID: 21576591 Link to research.