Keratin and permanent straightening treatments: what actually works, and who they suit

Every summer the same message arrives: "Can you make my hair stop frizzing?" Cambridgeshire is damp in winter and humid in a heatwave, and hair that looks fine at eight in the morning has doubled in size by lunch. Straightening treatments are the answer for a lot of people, but they are sold under a pile of confusing names, some of which mean the same thing and some of which very much do not.

So let me untangle them, in the order I would explain them to you sitting at my kitchen table with a cup of tea.

Why your hair frizzes in the first place

Frizz is not a personality flaw of your hair. It is physics. Each strand is covered in overlapping scales, the cuticle, and when those scales lie flat the hair is smooth and shiny. When they lift, moisture from the air gets in, the inside of the strand swells, and the hair puffs and tangles.

Some hair has a naturally raised cuticle. Some has been lifted by bleach, heat or years of hard water, which we have plenty of round here. Either way, every smoothing treatment on the market is trying to solve the same problem: keep the cuticle flat and stop the air getting in.

Brazilian blow dry, also called a keratin blow dry

This is the one I do most, and for most people asking the question it is the right answer.

A keratin-based smoothing product is applied to clean hair, left to work, then sealed in with a flat iron at a specific temperature. It does not permanently change the structure of your hair. What it does is fill and coat the cuticle so it lies flat, which means the hair dries faster, frizzes far less and sits sleeker.

Waves relax rather than disappear. Curly hair becomes loose waves rather than poker straight. That is why most people prefer it: you still look like you, you just look like you on a day when everything went right.

It lasts around three months, sometimes a little longer on hair that is not washed daily. It fades out gradually with no regrowth line to worry about, so there is no awkward stage and no deadline. It is safe on colour-treated hair, and it makes colour look glossier, so if you are having foils or balayage I will usually do the colour first and the treatment after.

Allow two to three hours depending on your hair, and expect to leave with hair that feels lighter than it did when you arrived.

Permanent straightening

This is a different animal. It is a chemical process that breaks and re-forms the bonds inside the hair, the same principle as a perm but working in the opposite direction. The result is properly straight hair that stays straight until it grows out.

Done well on the right hair, it is transformative. Done badly, or on hair that was not strong enough for it, it is the quickest way I know to destroy a head of hair, and the damage is not something a treatment fixes afterwards.

So I am careful with it. I only recommend it for hair that is in genuinely good condition, and I will not do it over recently bleached hair at all. Because it is permanent, you will see your natural texture at the roots as it grows, so it needs a top-up every four to six months, and the top-up has to be applied only to the new growth. Overlapping onto previously straightened hair is where breakage comes from.

Which one is right for you

If your hair is wavy, frizzy, or takes forever to blow dry, and what you really want is for it to behave, the keratin blow dry is your answer. It is the treatment I recommend most often because it solves the actual problem people have.

If your hair is very curly or coarse and you want it straight, full stop, then we should talk about permanent straightening, and I will want to see and touch your hair before either of us commits to booking it.

If your hair is fine, already fairly straight and just a bit fluffy, you may not need a treatment at all. A better cut, an Olaplex treatment and being shown how to actually use your dryer will get you most of the way, and I would rather sell you that than something you do not need.

If your hair is textured and you are weighing this against going natural, read how I approach textured hair first. Smoothing is a valid choice and I will do it properly, but it should be a choice rather than a default.

Who should not have one

Anyone whose hair is already snapping. Smoothing treatments involve heat and, in the permanent version, chemistry, and hair that is breaking now will break more.

Anyone who bleached in the last few weeks. We wait, and we rebuild first.

Anyone who is pregnant or breastfeeding should talk to their midwife or GP before booking any chemical smoothing service. I am a hairdresser and that is not my call to make for you.

And anyone hoping it will fix damage. It hides damage beautifully for a while, which is exactly why it is tempting, but the underlying hair is unchanged.

How to make it last

Wait. 48 to 72 hours before washing after a keratin treatment. Do not tie it up, do not tuck it behind your ears hard, do not clip it. Kinks set during this window and they set permanently.

Use a sulphate-free shampoo. This is not an upsell, it is the single biggest factor in how long your treatment lasts. Sulphates strip the treatment out. I will tell you which shampoo, and there are perfectly good ones on the high street.

Wash less. Every wash costs you a little of it. Two or three times a week is plenty for most people once the frizz has gone.

Stay out of chlorine for the first week, and after that wet your hair with clean water before you swim so it absorbs less.

Book the next one before it has fully worn off. A treatment applied to hair that is still partly smooth lasts noticeably longer than one applied to hair that has gone all the way back. Somewhere around the ten to twelve week mark is the sweet spot.

What it does to your routine

The part people do not expect is how much time it gives back. A client of mine used to spend forty minutes blow drying and straightening before work, five days a week. After a keratin treatment she rough dries it in ten and leaves. Over three months that is a lot of mornings.

You will also use fewer products, and your straighteners will come out less often, which means less heat damage. The treatment is one dose of heat in exchange for far less of it every day, and for most hair that is a good trade.

The names you will see online, translated

The marketing around this is a mess, so here is a rough translation.

Brazilian blow dry, keratin blow dry, keratin smoothing, keratin treatment. All broadly the same category of semi-permanent smoothing. Formulas differ, results are similar.

Cysteine treatment. A gentler smoothing option, often sold as the formaldehyde-free alternative. It smooths less and lasts less long, which for fine hair is sometimes exactly right.

Japanese straightening, thermal reconditioning, rebonding. These are permanent. They change the structure. Treat any of these words as the serious category, whatever the price.

Chemical relaxer. A different chemistry again, traditionally used on textured hair, and permanent. Not interchangeable with the above.

If a salon cannot tell you which category a treatment falls into, that is worth noticing.

A word about the formaldehyde question

It comes up, and it deserves a straight answer rather than a shrug.

Some keratin formulas release small amounts of formaldehyde when heated, which is why the good ones are used in ventilated spaces and why the flat iron temperature matters. Formulas have improved a great deal, and the ones I use are chosen with that in mind.

In practice it means I will open a window, I will not do your treatment in a cupboard-sized bathroom, and on a home visit I will ask for a room with some air. If you are sensitive to smells, tell me when you book and I will plan around it.

What it costs, and where to book it

Prices for both treatments sit on Fresha, where they stay accurate, and they depend on hair length and thickness rather than on a fixed rate, because a treatment on hair past your shoulder blades genuinely takes twice as long as one on a bob. You can see everything on my treatments list.

Both are available in the home salon in Yelling near St Neots, and as a home visit across Cambridgeshire including St Neots, Huntingdon, Cambourne and Cambridge. The full kit travels, so a home appointment is exactly the same service. I will just need a sink or shower to rinse at.

If you are not sure which one you need, send me a photo of your hair on a bad day rather than a good one, because that is the version I need to solve. I will tell you honestly which treatment I would use, and whether I think you need one at all. There is more from clients who have had them on the reviews page, and the rest of what I offer is on the services page.