INTRODUCTION
Current treatment of skin psoriasis achieves approximately
a 70% reduction in the Psoriasis Area Severity Index (PASI) with combination vitamin analogues plus corticosteroids, with up to 80% of patients experiencing clearance
with high potency topical steroids.1 Nevertheless, despite the success of treatment in skin psoriasis, treatment of nail psoriasis is challenging due to poor drug delivery, slow nail growth, and lack of a consistent algorithm. Topical penetration of the medication is difficult due to the proximal nail folds protecting
the nail matrix, and the overlying nail plate with nail bed hyperkeratosis protecting the nail bed. Treatment compliance is compromised by the extensive treatment time, pain with intra-lesional injections, close monitoring of systemic therapies, and adverse effects. Moreover, minimal published data exist to support
safety or efficacies of such treatments.2 Alternative treatments
have subsequently been pursued.
Indigo Naturalis has been used for centuries in traditional Chinese
medicine. The dried pigment, Qing Dai (QD), comes from the plants indigofera tinctoria, baphieacanthuscusia, isatis tinctoria, polygonum tinctorium, and isatis indigotica. It is thought to have antipyretic, anti-inflammatory, antiviral, antimicrobial, antitumor and detoxifying properties. For decades, it has been widely used to treat psoriasis, chronic myelogenous leukemia, and other infections
and inflammatory diseases in China and Taiwan.3 When taken orally, poor solubility, poor absorption, frequent irritation
of the gastrointestinal tract, and hepatotoxic side effects have been documented.4 Topical indigo naturalis ointments have been formulated to avoid first-pass metabolism and to reduce the toxic
metabolites that are produced when ingested.
Recent research has focused on evaluating the efficacy and safety of topical indigo naturalis on skin and nail psoriasis. In addition, studies have determined that the mechanism of action of indigo naturalis occurs through regulation of keratinocyte proliferation and differentiation, restoration of epidermal barrier
function, and anti-inflammation.9
Two early case reports described promising clinical improvement
in widespread, recalcitrant plaque psoriasis in two adults and one child. In lesions treated with topical indigo naturalis ointment, the amount of body surface area affected decreased by 100% in the child, and in addition to erythema, scaling, and induration of lesions, by 95% in the two adults. There were no side effects or adverse reactions documented. Additionally, liver
and renal functions remained normal in these patients, as in all of the subsequent studies reviewed in this paper.5,6
The first randomized, vehicle-controlled trial was published in 2007 to evaluate the efficacy and safety of topical indigo naturalis
ointment. Lin et al assessed the clinical and histological effects of indigo naturalis ointment on recalcitrant plaque-type
