Keratin on your hair: what the salon one does that the bottle from the shop doesn't

Hair · 15 September 2026 · by María José Esteve

The keratin mask works. The thing is, it does something different from salon keratin, and mixing the two up is what leads to disappointment.

You're already wearing keratin

Before we talk about bottles: keratin isn't a treatment. It's the protein your hair is made of, almost entirely.

When hair takes a beating (bleaching, daily straightening, sun, chlorine) it gradually loses some of that protein from the outside. The surface is left open, the hair turns rough, it takes up moisture from the air and frizzes. Everything with “keratin” on the label is trying to fill that gap.

The difference is in how much it fills. And in how long it lasts.

What a shop shampoo or mask does

They contain hydrolysed keratin, which is keratin broken into tiny pieces so it fits in a shampoo. It settles on the outside of the hair, fills the open areas a little and leaves the hair softer to the touch. It works. You notice it when you blow-dry.

But nothing fixes it there. In one or two washes it's gone, and while it's on, the hair still reacts to moisture exactly as it did before, so the day Valencia wakes up muggy the frizz comes back as if you'd put nothing on.

Notice the word that usually goes with these products: effect. Smooth effect, keratin effect. It's not there by chance.

And careful, this isn't a dig at the bottle. If your hair is fine and all you want is for it to be soft and shiny, a keratin mask from the perfume shop does exactly that, and you don't need anything else.

The home-use kits

They're another story. They're closer to what we do here, because the product is sealed with straighteners, and that's exactly where the most can go wrong.

The roots, the mid-lengths and the ends don't need the same amount of product, and at home the same amount usually goes on everything. Where there's too much, the hair ends up clumped and looking dirty. Where there's too little, it frizzes within a week. Then there's the straightener: running it slowly, thin section by thin section, round the back of your own neck is very hard, and the temperature the box tells you is the same for healthy hair as for bleached hair, which doesn't take it the same.

If the kit asks you to air the room or not to breathe in the fumes from the straightener, do as it says.

What changes when we do it in the salon

The product goes on section by section, with the amount each area needs. It's left on for the right time, dried, and then sealed with straighteners, pass by pass and in thin sections, at the temperature your hair can take and not the one on some box. That's why it lasts months and not washes.

It's worth knowing what it does and what it doesn't. Keratin controls frizz and leaves the hair manageable, shiny, easy to style. It doesn't leave it poker-straight: if you have a wave, the wave softens, but it's still there. If what you want is really straight, that's another treatment (nanoplasty), and we do that too.

What decides isn't in the bottle: it's in your hair

Before we put anything on, we look at it. How thick it is, how much water it absorbs (which is what we call porosity), whether there's colour or bleaching underneath, how much curl there is. And what you want from it, because getting out of a fight with the hairdryer isn't the same as wanting different hair.

With that in front of us, often the answer isn't even keratin.

• Very damaged hair, from one bleaching after another: rebuilding first. On a broken fibre keratin doesn't grab, and you'd waste the treatment in three weeks.
• Fine hair with no body: keratin can flatten it even more. There, hair “botox”, which fills, usually works better.
• Dry hair from sun or hairdryer, nothing more: a hydration treatment is more than enough.
• Frizzy, wanting straight: nanoplasty.

So, bottle or appointment?

The bottle, if your hair is healthy, frizzes little and you want softness and shine between washes.

The appointment, if the moisture lifts it every morning, if you don't leave the house without half an hour of straightening or if the hair won't be styled no matter how much you put on it. That's no longer fixed by anything that rinses out in the shower.

And if you've done a kit at home and it's come out patchy, don't put another one on top to even it out. Come as you are and we'll take a look.