Ask three salons which smoothing treatment you should have and you will get three confident, contradictory answers. Ask the brands and it gets worse: one is “organic”, another is “chemical-free”, a third is “nano-technology”. Almost none of it means anything.
We have been performing these treatments across our salons since long before nanoplastia had a name. Here is what actually separates them, written by people who do the work rather than sell the bottle.
Start with what hair is
Every one of these treatments has to get past the cuticle to reach the cortex. That journey is the entire reason heat is involved.
When cuticle scales lie flat, light reflects evenly and hair reads as glossy. When they lift — from heat, alkalinity or friction — light scatters and the same hair reads as dull and frizzy. A large part of what any smoothing service delivers visually is simply persuading the cuticle to lie flat again.
What all three have in common
This is the part the marketing skips.
Every one of these treatments works the same way in principle: an acidic solution is applied to the hair, then sealed in with a flat iron at high heat. The heat is not optional and it is not incidental — it is what makes the chemistry work.
So when a treatment is described as chemical-free, be sceptical. Water is a chemical. More to the point, the active ingredient in every system on this list is an acid chosen precisely because it restructures hair. That is the whole idea. A treatment that changed nothing about your hair’s structure would not smooth it.
Three bonds, three permanences
Inside the cortex, keratin chains are tethered to each other three different ways. They differ enormously in strength, and that difference explains everything about how long a treatment lasts.
Only the disulphide bond is permanent. It is covalent — a genuine chemical link between sulphur atoms — and breaking it changes hair’s structure until it grows out. Hydrogen and salt bonds re-form every time hair dries or returns to a neutral pH, which is why a blow-dry is temporary.
Hold onto that. It is what separates the treatments below from each other, and from rebonding.
Keratin, or the Brazilian blowout
The original, and still the most effective if your goal is genuinely straight hair.
Keratin treatments add hydrolysed keratin protein — the same protein your hair is largely made of — and seal it in with heat. On coarse, thick or strongly curly hair, nothing else on this list matches it for sheer straightening power.
The complication is historical. Traditional Brazilian systems relied on formaldehyde or formaldehyde-releasing compounds to lock the result in place, and formaldehyde is a recognised human carcinogen. That is not a marketing scare; it is why the entire category has spent fifteen years looking for alternatives, and why ventilation in the salon matters as much as the product itself.
Modern keratin systems vary enormously. Some are still formaldehyde-based. Some are not. The question worth asking your stylist is not “is this keratin?” but “what is the active in this particular system?”
Cysteine
Cysteine treatments were the industry’s first serious answer to that problem.
They use glyoxyloyl carbocysteine — a derivative of an amino acid your hair already contains — at a pH much closer to that of hair and scalp than a traditional Brazilian solution. Gentler chemistry, gentler result.
That last part is the honest trade-off, and the one clients are rarely told. Carbocysteine smooths the cuticle and reduces frizz very effectively. It is considerably less effective at actual straightening. If you arrive with tight curls expecting poker-straight hair, cysteine will disappoint you. If you arrive with frizz-prone waves wanting them calmer and easier to manage, it is often the better choice precisely because it does less.
It is also worth knowing that the ironing stage in cysteine treatments has been shown to release small quantities of formaldehyde as a by-product of the reaction. Small, but not zero.
Nanoplastia
The newest of the three, and the one carrying the most marketing weight.
Nanoplastia systems typically combine carbocysteine with glyoxylic acid, along with amino acids, oils and conditioning agents. The “nano” refers to particle size — the claim being that smaller particles penetrate the hair fibre more deeply.
Two things are worth understanding. First, these solutions are strongly acidic — commonly around pH 1.5 to 2, markedly lower than a cysteine treatment. Gentler ingredients at a harsher pH is not automatically gentler overall.
Second, carbocysteine does not straighten hair by itself. It straightens when combined with glyoxylic acid, which is an aldehyde. And glyoxylic acid systems have been reported to release small amounts of formaldehyde under the heat of the flat iron, despite being marketed as formaldehyde-free.
None of which makes nanoplastia a bad treatment. It produces excellent results, particularly on hair that needs conditioning as much as smoothing. But “formaldehyde-free” is not the same claim as “damage-free”, and the two get conflated constantly.
So what actually differs
Set the four services side by side against the three bonds, and the honest picture appears.
Rebonding breaks the disulphide bond, so the result is permanent and so is the structural cost. The three treatments people actually compare are the same operation performed with different acids at different pH — reform the weak bonds under heat, seal the cuticle. None of them restructures hair permanently, which is why every one of them fades rather than growing out.
If a salon tells you a smoothing treatment is permanent, they are either describing rebonding or they are wrong.
How to actually choose
Forget the category names and answer three questions.
How straight do you want it? Genuinely straight, from tight curl — keratin. Smoother and softer, still with movement — cysteine or nanoplastia.
What has your hair already been through? Recently bleached, heavily highlighted or previously chemically straightened hair needs an honest assessment before any of these. A good stylist will sometimes tell you to wait. That is not them losing a sale; it is them not breaking your hair.
What will you do afterwards? This matters more than the treatment you choose.
Aftercare is not optional
The result lives or dies on what you wash it with. Sulphates strip the treatment. Two clients can have the same service on the same day and get months of difference out of it purely on what happens in the shower afterwards.
There is no single right product, and we are not going to pretend one brand covers every case. What suits you depends on which treatment you had, what your hair was like before it, and how hard your water is. We have gathered what our stylists actually recommend into one place — Smoothing Aftercare — across Kérastase, L’Oréal Professionnel, QOD, K18 and De Fabulous.
Broadly:
After any smoothing service, a sulphate-free cleanser is the baseline. Kérastase Discipline Bain Fluidéaliste suits frizz-prone and colour-treated hair, which is the combination most smoothing clients are managing. De Fabulous Reviver is a gentler-priced alternative that does the same job.
After a keratin or Brazilian service, QOD MAX PRIME was formulated specifically to extend that result — shampoo and mask designed as aftercare rather than adapted into it.
After chemical straightening, L’Oréal Xtenso Care is the matched aftercare for that service, sulphate-free in both shampoo and masque.
If your hair was already damaged going in, K18’s leave-in molecular repair mask works alongside any of the above rather than replacing them.
The hard water problem
There is a second issue specific to where we live, and it defeats good aftercare routines regularly.
Much of Gujarat runs hard water, and hard water deposits calcium into the hair shaft. That calcium stiffens hair, dulls colour, and shortens the life of a smoothing treatment regardless of how well it was applied. It is the single most common reason a treatment that should have lasted months starts fading in weeks — and no amount of gentle shampoo fixes it, because the problem is mineral, not detergent.
Two ranges address it directly. Kérastase Première is a decalcifying system that removes accumulated calcium rather than working around it. L’Oréal Metal DX does the same job at a lower price point, and its pre-shampoo treatment is the more thorough option if build-up is severe.
If your water is hard and your treatments never seem to last, start there before you blame the service.
Not sure which is right for you? Book a consultation at any Reflexions salon and we will assess your hair before recommending anything. If the answer is that you should wait, we will tell you that too. See our hair services, browse Smoothing Aftercare, or ask our Beauty Advisor.