Does Indigo Cause Leukoderma? The Real Story Behind the Henna Myth
Indigo and natural henna themselves rarely cause leukoderma (pigmented contact dermatitis). Most reported cases trace to 'black henna' or poor-quality henna adulterated with PPD or heavy metals. Here is the real story, with the research.
A note first. What follows mixes things I heard while meeting people in the henna and salon trade with what I confirmed in the research while preparing our MFDS approval. Some of the trade talk is unverified, so please read it in that light. The short version: indigo and natural henna themselves very rarely cause leukoderma.
What Is Leukoderma?
The question began with a customer enquiry passed on by a retailer: "I heard indigo can cause leukoderma… do I really need indigo to dye my hair brown?" How did indigo come to carry that reputation?
Leukoderma (Riehl's melanosis) is a form of pigmented contact dermatitis in which the skin darkens. And numerous sources tie it to PPD in hair dyes. In other words, a chemical colorant like PPD sits at the centre of this issue from the start.
Why Did Indigo Get the Blame?
I believe indigo became linked to leukoderma through three overlapping currents: a belief that the "henna incident" was caused by indigo, a run of alarming articles about dermatitis after henna dyeing, and the MFDS ban on the distribution of 100% Indigofera powder, which hardened the misunderstanding.
The idea that the "henna incident" was indigo's fault is at odds with the facts. Photographs of skin darkened by leukoderma stirred real fear, yet natural indigo on its own only dyes blue. What reliably darkens to black is PPD. So the cause of the leukoderma cases points naturally to PPD, not indigo.
What Does the Research Say?
Even in the EU SCCS report on henna leaf powder (100% henna), the focus is less on the word "leukoderma" than on black henna — henna that is not 100% natural. Prolonged exposure to the PPD added to it produced swelling or darkening of the face after a lag of one day to two weeks, while side effects from henna itself were reported as very rare.
The review it cites (Antoon C. de Groot, "Side effects of Henna and semi-permanent 'black Henna' tattoos: a full review," Contact Dermatitis 69:1–25, 2013) finds that most dermatitis cases were caused by added PPD, and that where PPD was absent, heavy metals, strong acids or particular chemical colorants were usually involved instead. There are, very rarely, a couple of 1980s cases in which natural henna at an uncertain concentration caused dermatitis. But even setting aside henna's ancient use across India and the Middle East, decades of research show dermatitis from henna to be exceedingly rare. It makes no sense that side effects would be so common only in Korea.
Market Turmoil Amplified the Myth
And yet we met "henna side effects" in article after article. The state of the market played a part. Korea's henna market grew quickly through network selling, and as participants multiplied, some sellers reportedly distributed henna with heavy metals above the limit, "henna" recklessly dosed with PPD to dye faster, and even old, spoiled henna. Real dermatitis arose from these poor-quality products, and in the process natural henna and indigo as a whole were tarred with the same brush. (This part I heard directly from a henna seller who had struggled with regulatory action.)
The MFDS Ban on 100% Indigo Powder
Then, a few years ago, sellers received a notice: from 2025, the sale of 100% Indigofera powder would be prohibited. As it happened, when the measure landed, even the sellers began to wonder aloud whether indigo really was the problem — I watched it happen. Stylists grew uneasy about indigo too.
But as covered in indigo side effects, this ban is not because indigo is dangerous. Above a certain concentration, Indigofera powder can cause itching, so Europe restricted the unguided sale of neat 100% powder, and Korea followed the same standard. (Water Henna Indigo was properly approved even within these restrictions.)
Indigo Is Actually an Excellent Colorant
In fact, the indirubin in Indigofera powder is reported in research to have anti-inflammatory properties, and in the EU SCCS assessment indigo rates as even safer than henna — with a safety margin, as I recall, about three times higher under the MFDS cosmetic risk-assessment guideline. It is a shame for so fine a natural colorant to be tied to a skin disease.
In the end, consumers came to misunderstand natural henna and indigo through a mix of a fast-growing market, the poor-quality products within it, and confusion as policy was sorted out. Water Henna entered this misunderstood market late, so I leave this note in the hope that a health-conscious natural dye will one day be judged fairly again. How the colours are made is laid out in the henna and indigo colour guide.