Indigo Naturalis for Psoriasis

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.^[1] 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.^[2] 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

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

Indirubin affects the increased number of skin cells proliferating at one time in psoriasis.^[3] 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.^[3]

Tryptanthrin

Tryptanthrin decreases IL-17, an important signaling molecule that promotes inflammation and is known to be increased in psoriasis.^[4]

Whole Herb

Indigo naturalis as a whole herb improves skin cell connections, which are very important for normal skin function.^[5]  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.^[5] 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.^[6] 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.^[7] 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.^[7]

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.^[8] 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.^[8]

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.^[11] Additional cases of successful nail psoriasis treatment with indigo naturalis oil extract have been documented.^[12] 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.