The Complete Guide to the Brazilian Blow Dry in London (2026)

A note on names: this treatment goes by many - Brazilian blow dry, BBD, keratin blow dry, keratin treatment, Brazilian keratin treatment. In the UK they overwhelmingly describe the same family of service. This guide uses Brazilian blow dry throughout. And to clear the other confusion up front: a Brazilian blow dry smooths - it is not a perm, and it is not a relaxer.

I have been doing texture work since 1991 - three decades plus of taking hair straighter, curlier, and everywhere in between - and the Brazilian blow dry is the service I am asked about most. It is also the one surrounded by the most marketing fog. This page is the reference I wish clients arrived with: what it is, who it genuinely suits, what it costs in London, how long it lasts, the safety picture told honestly, and how to keep the result.

WHAT A BRAZILIAN BLOW DRY ACTUALLY IS

A Brazilian blow dry is a semi-permanent smoothing treatment. A working solution is applied to the hair, then sealed in with tension and heat - blow dry and straightening irons. The result is hair that behaves: dramatically less frizz, faster drying, more shine, waves loosened rather than erased.

Two things follow from that definition, and they answer most of the questions I hear in consultation.

First, semi-permanent. Unlike a perm or Japanese straightening, it does not permanently rebuild the hair’s internal bonds. It softens and coats the fibre’s behaviour for a period of months, then fades progressively. There is no hard regrowth line.

Second, smoothing, not straightening. A BBD will not turn a strong curl into glass-flat hair, and it is the wrong tool for that job. What it does superbly is take frizzy, unruly, wavy or loosely curly hair and make it smooth, manageable and quick to style. Clients who want truly straight, permanent results need a different conversation - our hair straightening guide maps the whole territory.

WHO IT SUITS - AND WHO IT DOES NOT

The ideal candidate has frizzy, wavy or loosely curly hair that fights humidity and takes too long to blow dry. Colour-treated and highlighted hair is usually workable - often the treatment improves how coloured hair feels - but condition is assessed first, and the treatment is sequenced around colour appointments, never on the same day without a plan.

It is the wrong service for hair wanting volume (it will lie flatter), for very fine hair that relies on lift, and for anyone expecting permanent straightness. And there are cases where my answer is no: severely compromised hair, active scalp conditions, and - as a precaution I hold to - pregnancy and breastfeeding. A salon that never says no is not assessing you.

WHAT IT COSTS IN LONDON

London pricing for a Brazilian blow dry runs a wide range, and the spread is not arbitrary. The honest anatomy of the price: the formula used (quality varies enormously), the stylist’s time (a proper service is two to four hours, and long or dense hair takes more), the consultation and strand assessment around it, and yes, the postcode.

My own current prices are always on the booking page - they live there so this guide never quotes a stale figure.

Cheap versions exist. What they economise on is the formula, the time, or both - and with this service, the formula and the time are the service.

HOW LONG IT LASTS

Three to four months is the honest window for most hair, sometimes stretching towards five or six with disciplined aftercare and depending on how often you wash. It fades gradually - the hair drifts back towards its natural pattern rather than snapping back on a given day. Many clients settle into a rhythm of three treatments a year.

THE SAFETY QUESTION, TOLD STRAIGHT

This is the section most salon websites skip. You should not book this service anywhere that cannot discuss it.

The original Brazilian treatments earned their controversy: formaldehyde, or ingredients that release it when heated. That era created the rules a responsible salon works by now - and the marketing fog, because “formaldehyde-free” on a label is the beginning of the question, not the end of it. Some replacement systems release formaldehyde in use; others swapped to different active chemistry entirely.

The main modern alternative, glyoxylic acid, is itself under formal EU safety review right now - the SCCS was mandated in May 2026 to assess it, with an opinion due in 2027. We have written up what that review actually means for your appointment, and our position is informed consent: you are told what system is being used on your head, what is in it, and why it was chosen for your hair. Well-ventilated space, correct technique, honest labels.

There are also chemical rules that never bend, whatever the brand on the bottle - what can and cannot sit over bleach, why strand tests precede chemistry, why certain systems never mix.

WHAT HAPPENS ON THE DAY

A consultation and strand assessment first - condition, history, what you want the hair to do. Then: a cleansing wash to open the hair, application of the working solution section by section, development time, blow dry, and the sealing pass with irons. Two to four hours depending on length and density. You leave with the finished result, not a waiting period - modern systems are largely wear-and-go, though the first days still have rules (below).

AFTERCARE - WHERE THE RESULT IS KEPT OR LOST

The treatment sets the ceiling; aftercare decides how close to it you live.

Washing: sulphate-free shampoo, nothing stripping. Every wash from now on is either preserving the treatment or shortening it.

The first days: follow the specific window your stylist gives you for washing, tying and pinning - it varies by system, and with some it is measured in days, not hours. When in doubt: leave the hair down and dry.

Swimming: chlorine and salt water are the treatment’s fastest enemies. Wet the hair with clean water and coat it before pools or sea, rinse promptly after.

Heat: you will need far less of it - that is the point. When you do iron, moderate temperature; the treatment has already done the heavy lifting.

FREQUENTLY ASKED QUESTIONS

Is a Brazilian blow dry the same as a keratin treatment? In UK salon usage the names overlap almost completely - both describe heat-sealed semi-permanent smoothing. What differs is the specific system and formula, which varies more within each name than between them. Ask what system the salon uses; that is the real question.

Will it make my hair completely straight? No - it smooths and loosens. Frizz drops dramatically, waves soften, drying time shortens. If you want permanently straight hair, that is a different service and a different conversation.

How long does a Brazilian blow dry last? Three to four months for most hair, occasionally longer with careful aftercare. It fades gradually with no regrowth line.

Can I have one over coloured or highlighted hair? Usually yes, subject to a condition check - it often improves how coloured hair behaves. Timing matters: colour and smoothing are sequenced, and heavily lightened hair needs a strand test first, every time.

Is it safe? What about formaldehyde? With honest labelling, correct technique and ventilation, a properly chosen modern system is a managed, understood risk - but “formaldehyde-free” claims deserve scrutiny, and the main alternative chemistry is under EU review with an opinion due in 2027. Any salon that waves the question away has answered a different question about itself.

Can I have it done while pregnant or breastfeeding? My answer is no - not because harm is proven, but because it cannot be ruled out to my satisfaction, and a few months’ wait costs nothing. Not every salon holds this line; I do.