Why Henna Dyeing Fails — Damaged Hair, Not the Henna
The main reason henna dyeing fails is damaged hair. Henna's natural pigment, lawsone, binds well to intact keratin, so on hair damaged by bleach or chemical dye the colour does not take evenly. Here is what a failure really tells you.
Here is the short answer: the main reason henna dyeing fails is that the hair is damaged. Henna's natural pigment, lawsone, binds well to intact keratin, so on hair worn down by bleach or chemical dye the colour does not take evenly. Coating your head in henna only to have it not take is genuinely maddening, so here is what I found when I looked into why.
I Have Had "Failed" Dyes Too
Recently a customer left two stars, saying Water Henna would not take. And once, when I sent a big batch to my four aunts, only the eldest's took — the rest did not, and I even heard "isn't this a scam?" When you have gone to the effort and it will not take, of course you are angry. In my powder-henna days I failed often too, and back then I simply assumed I had bought a "dud" henna.
The Clue Came from a Bleached Hair Swatch
Then I remembered a sample: Water Henna applied to bleached hair. Here is the background. To earn a functional-cosmetic designation from the MFDS, a product goes through tests at an accredited lab, and the dyeing-performance result that came back was so even and rich that I wanted it for the product page. So I bought similar white-hair swatches to photograph myself — and no matter what I did, the colour came out patchy and dull.
Puzzled, I called the lab and asked what kind of white hair they used to get such clean results. "Just plain white hair," they said. Just plain white hair? Was not all white hair the same? It turned out the swatches I had bought were bleached. Henna simply does not take well on bleached hair.
Why Won't Damaged Hair Hold Henna?
The reason lies in how it binds. Lawsone bonds with the hair's keratin — more precisely, it forms disulfide bonds with the amino-acid chains of the keratin protein. That bond raises the protein's stability and helps the hair resist physical stress. Put the other way around, it is also why a perm's reducing agent takes less easily on henna-treated hair.
The problem is hair whose keratin is already damaged by bleach or chemical dye. On dry, damaged strands, lawsone is absorbed unevenly or barely binds at all. So we arrive at a slightly rueful conclusion: for henna to take well, the hair must be healthy — even though people reach for henna to make their hair healthy in the first place.
Looking back at my aunts confirmed it. The eldest, who had only ever used henna, took the colour instantly; the others had been using herbal or ordinary chemical dyes.
If It Failed, Please Don't Be Discouraged
So if you tried henna and it failed, I hope you will not take it too hard. See it instead as learning the true state of hair tired out by perms and chemical dyes. Keep at henna from there, and as lawsone binds with your keratin it will gradually firm and settle the hair — and the colour will take better over time. If the powder routine is a chore, see how to use the liquid Water Henna.
One aside: this bleached-swatch failure sent me leafing through the cosmetics regulations, where I found that dyeing pure white hair or wool is also accepted. So I got some wool, dyed it with Water Henna, and it came out exactly as rich and even as the lab's result — which is how I finally got the dyeing photos for the product page.