Henna or hair dye: what’s the difference, and how to choose?

Henna, conventional chemical dye or a two-step 100% plant-based colour: three very different families, three results, three ways of treating your hair. The trouble is that all three get lumped together under the word "colour", and the confusion leads to disappointment. People try one thing expecting the result of another, conclude that "plant-based colour doesn't work", and go back to the bottle. So let's tell them apart, plainly, so you can choose the right one for what you actually want.

Henna: one plant, one shade, a few limits

Henna is a single plant, Lawsonia inermis, dried and ground into a powder. Mixed with warm water, it releases a pigment (lawsone) that binds to the surface of the hair and leaves a warm, coppery-red tone. It conditions the fibre, adds shine and is genuinely kind to the scalp. For anyone who wants exactly that red, used on its own, it can be lovely.

The limits show up the moment you want something other than red. Pure henna only gives one family of shades. To reach a chestnut, a brown or a deep near-black, you need to combine it with other plants such as indigo, cassia or amla, and you need to know how. On its own, henna also doesn't reliably cover greys to a natural-looking result, and it can lean brighter than expected. It's a beautiful ingredient, but a single ingredient is not a complete method.

Conventional chemical dye: powerful, but at what cost?

Conventional permanent dye works by opening the hair cuticle with ammonia (or a substitute), then using an oxidant such as hydrogen peroxide to develop synthetic pigments deep inside the fibre. This is what makes the chemistry so versatile: it can lighten, go cool or ashy, and shift you several shades in one sitting. If you want to go lighter or reach a genuinely cool blonde, chemistry is, honestly, the only thing that does it.

That power has a price. Ammonia, PPD, resorcinol and oxidants are aggressive on the hair fibre and can irritate a sensitive scalp. Over time, repeated lifting leaves hair drier and more porous, and the regrowth line can be unforgiving. None of this makes chemical dye "bad" — it's simply a trade-off. You're buying reach and coolness, and you're paying for it in fibre health. Worth knowing before you decide it's your only option.

Two-step 100% plant-based colour: the best of both worlds

This is where things have genuinely moved on. A plant-based hair colour doesn't have to mean "henna and a bit of guesswork". Our co-founder Jung Ae built a method around the one thing most plant colour gets wrong: preparation. Elsewhere, the prep step is skipped or barely explained, the colour doesn't take, and people blame the plants. The plants were never the problem — the method was.

The Tresse Paris approach is a two-step ritual. The first sachet prepares the fibre so it's ready to receive pigment. The second sachet is the colour itself, a blend of plants such as henna, indigo, cassia and amla. The detail that changes everything is the thermometer included in the box: plant pigments only reveal their true depth at the right temperature, so instead of hoping, you measure. We didn't invent plant colour — we improved the experience and the reliability of it, the way you'd refine a familiar object rather than reinvent it.

The result sits between the two worlds. You get a colour that sheaths and strengthens the hair fibre and respects a sensitive scalp, with no ammonia, no PPD, no resorcinol and no oxidant. It's COSMOS Organic, made in France, and won the Natexbio Challenge in 2024. On darker shades it covers greys close to 100%. What it cannot do — and we'll always say so — is lighten your hair.

Henna, chemistry or plant-based: how to choose?

Start from the result you're after, not from the category. A few honest pointers:

• You want to go lighter, or reach a cool, ashy tone. Only chemistry does this. Plant-based colour and henna deposit warm tone; they never lift. If lightening is the goal, no plant will get you there — that's just how it works.
• You want a single coppery-red and nothing else. Henna on its own can suit you well.
• You want a warm, natural-looking brown, chestnut, caramel, auburn or mocha, with grey coverage and healthier hair. Two-step plant-based colour is built for exactly this.
• Your scalp is sensitive, or you simply want to step away from harsh chemistry. Plant-based is the gentle route, provided the method is followed.

The honest line on tone: plant colour pulls warm. Caramel, copper, golden, mocha, auburn and chestnut are all within reach. Ashy, cool, pale or anything that involves lightening is not — and anyone who promises otherwise with plants alone isn't being straight with you.

And what about upkeep?

Maintenance differs by route. Chemical colour gives a sharp regrowth line and usually needs root touch-ups every three to four weeks, plus care to manage the dryness. Plant-based colour fades far more softly: the tone settles in the first few days, then loosens gradually rather than leaving a hard line, so the grow-out is gentler on the eye. Because it deposits with each application, the colour also builds depth over time. A refresh every four to six weeks keeps it vivid, and since it conditions rather than strips, your hair tends to feel better the longer you stay with it — the opposite of the chemical cycle.

Frequently asked questions

Are henna and plant-based colour the same thing?

Not quite. Henna is one plant used on its own. A two-step plant-based colour is a complete method: a preparation step, then a blend of several plants (henna, indigo, cassia, amla) applied at a controlled temperature. Henna is one ingredient; the method is the whole recipe.

Can plant-based colour lighten my hair?

No. Plant pigments only deposit tone — they darken, enrich, refresh and cover, but they never lift. If you want to go lighter, only chemical lightening can do that. We'd rather tell you plainly than let you expect something the plants can't deliver.

Does plant-based colour really cover greys?

On darker shades, yes — close to 100% when the two-step method is followed and the thermometer is used. On very light or cool target shades, results are softer, because plant colour works by adding warm tone rather than by lifting. The darker the chosen shade, the stronger the coverage.

Is plant-based colour gentler on the scalp than chemical dye?

It's formulated to be. With no ammonia, no PPD, no resorcinol and no oxidant, it's designed for sensitive scalps and sheaths the fibre rather than stripping it. As with any cosmetic, a patch test before your first application is sensible.

How often should I reapply?

Every four to six weeks keeps the colour vivid, though it depends on how fast your hair grows and how much grey you're covering. Because plant colour builds with each use and conditions as it goes, regular reapplication tends to leave hair looking and feeling healthier over time.