Ingredient guide
Glyoxylic acid hair treatment.
The active smoothing ingredient in modern formaldehyde-free keratin treatments. What it is, how it works, what the safety data says, and which products use it.
The basics
What is glyoxylic acid?
Glyoxylic acid is a small organic molecule — formula C2H2O3 — that has become the active ingredient in many modern hair smoothing treatments. It is the compound that actually does the smoothing in most formaldehyde-free keratin treatments on the market today.
In plain terms: glyoxylic acid is small enough to penetrate inside the hair strand. Once there, it forms new chemical bonds between the keratin proteins that make up your hair. These new bonds hold the hair in a smoother, straighter shape — reducing frizz, loosening curl patterns, and making hair significantly easier to manage.
Unlike older formaldehyde-based treatments, glyoxylic acid does not permanently destroy the hair's natural structure. The new bonds it creates are semi-permanent — they gradually relax over 3 to 5 months, allowing the hair to return to its original texture. This makes glyoxylic acid treatments reversible, which is a significant advantage over both formaldehyde treatments and alkaline relaxers.
Chemical name
Glyoxylic acid
Formula
C₂H₂O₃
Results last
3–5 months
Formaldehyde
Zero
The science
How glyoxylic acid smooths hair.
01
Penetrates the cortex
When applied to wet, clean hair, glyoxylic acid molecules are small enough to pass through the hair cuticle and enter the cortex — the structural core of the hair strand. This is where the keratin proteins and their bonds live.
02
Heat activates new bonds
When you pass a flat iron over the treated hair, the heat activates a chemical reaction. The glyoxylic acid forms new cross-links between keratin protein chains inside the cortex. These new bonds lock the hair into a smoother, straighter configuration.
03
Reshapes without destroying
Crucially, glyoxylic acid does not break the hair's natural disulfide bonds — the strong internal bonds that give hair its shape. Instead, it adds new bonds alongside them. This means the treatment is semi-permanent: it reshapes the hair temporarily without irreversible structural damage.
Comparison
Glyoxylic acid vs formaldehyde.
Glyoxylic acid
Formaldehyde content: None — completely different molecule
Fumes during application: No formaldehyde added; traces can be released at flat-iron heat — ventilate
Mechanism: Creates new bonds alongside existing structure
Permanence: Semi-permanent (3–5 months)
Damage profile: Does not destroy disulfide bonds
Home use: Safe for home application — no special ventilation
Regulatory status: Permitted in EU cosmetics at regulated concentrations
Formaldehyde
Formaldehyde content: Contains or releases formaldehyde when heated
Fumes during application: Releases toxic gas — eye and throat irritation
Mechanism: Cross-links proteins but with carcinogenic byproduct
Permanence: Semi-permanent (2–4 months)
Damage profile: Can damage hair with repeated use
Home use: Not recommended — requires commercial ventilation
Regulatory status: Classified as a known carcinogen (IARC Group 1)
Glyoxylic acid was developed specifically to replace formaldehyde in hair smoothing treatments. It delivers comparable smoothing results through a fundamentally different chemical mechanism — without producing carcinogenic fumes or requiring industrial ventilation during application.
Safety profile
Is glyoxylic acid safe for hair?
Glyoxylic acid has been used in cosmetic formulations for years, and at standard cosmetic concentrations it has a well-established safety profile. There are over a substantial body of published toxicology literature, alongside the ANSES findings above and the EU review now under way.
The ANSES report (2024)
In October 2024 the French national health and safety agency ANSES issued an alert about hair-straightening products containing glyoxylic acid. In January 2025 it confirmed that glyoxylic acid was \u201cvery likely responsible\u201d for five reported cases of acute kidney failure, and recommended that the EU consider restricting or banning it in cosmetics. The EU\u2019s Scientific Committee on Consumer Safety began its assessment in May 2026.
This is worth taking seriously, and we do. However, the context is important:
- The reports were linked to specific products at very high concentrations — not to glyoxylic acid as a category.
- The mechanism of concern involves glyoxylic acid metabolising to oxalic acid at high doses, which can affect kidney function. This is a dose-dependent effect — concentration matters.
- The broader toxicological literature (the published literature) is mixed: effective at cosmetic concentrations, with the kidney-toxicity concerns ANSES raised still under EU review.
- No equivalent safety signals have been reported for products using glyoxylic acid at standard regulated concentrations.
What this means for QIQI Hair Controller
QIQI Hair Controller is formaldehyde-free and uses glyoxylic acid as its active, as its published ingredient list shows. ANSES did not publish the names of the products involved in the reported cases, so we cannot claim QIQI was or was not among them. What we can say: follow the manufacturer's instructions exactly, keep the product 0.5cm off the scalp, and work in a well-ventilated room when flat-ironing.
We would rather give you the full picture than sell you a treatment you would regret. If the ANSES findings concern you, Nanokeratin System is the alternative we stock \u2014 the manufacturer states their smoothers are 0% formaldehyde and aldehyde.
Products using glyoxylic acid
QIQI Hair Controller.
Three formulas matched to different hair types — all formaldehyde-free, all using glyoxylic acid at safe, tested concentrations. Designed for both salon and home use. Results last up to 5 months.
From £129 · 150g
Hair Controller — Thick & Coarse
Formaldehyde-free permanent smoothing treatment for thick, coarse, and afro-textured hair. Softens disulfide bonds under heat for lasting frizz control — from defined curls to fully straight. QIQI Hair Controller results last up to 5 months.
Shop now →
From £129 · 150g
Hair Controller — Wavy & Curly
Permanently reduces frizz and enhances natural pattern definition — or delivers a smooth, controlled finish. Designed specifically for wavy and curly hair. Formaldehyde-free. Lasts up to 5 months.
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From £129 · 150g
Hair Controller — Thin & Delicate
Formaldehyde-free permanent smoothing for fine, colour-treated, or delicate hair. Eliminates frizz and reduces volume without over-processing. QIQI Hair Controller safe for bleached and highlighted hair. Results last up to 5 months.
Shop now →Common questions
Glyoxylic acid — FAQ
What is glyoxylic acid in hair treatment?
Glyoxylic acid is a small organic molecule used as the active smoothing ingredient in many modern formaldehyde-free keratin treatments. When applied to the hair and activated by heat from a flat iron, it penetrates the hair cortex and forms new cross-links between keratin proteins. This reshapes the hair fibre from the inside, reducing frizz and curl without permanently destroying the natural disulfide bonds. The result is semi-permanent smoothing that lasts 3 to 5 months and gradually washes out.
Is glyoxylic acid safe for hair?
At the concentrations used in professionally formulated hair treatments, glyoxylic acid has a well-documented safety profile. In October 2024 the French agency ANSES issued an alert about hair-straightening products containing glyoxylic acid, and in January 2025 it confirmed the ingredient was “very likely responsible” for five cases of acute kidney failure. ANSES advises consumers to avoid products containing it, and has asked the EU to consider restricting or banning it; the EU’s safety committee began reviewing it in May 2026. It is not currently restricted in the UK or EU. Keep the product off the scalp, follow the processing times, and ventilate the room when flat-ironing. As with any chemical hair treatment, following the manufacturer instructions is essential.
Is glyoxylic acid the same as formaldehyde?
They are different chemicals. Formaldehyde (CH2O) is a known carcinogen, and treatments built on it release it as a gas throughout the service. Glyoxylic acid (C2H2O3) contains no formaldehyde — but it is an aldehyde-type acid, and published testing shows small amounts of formaldehyde can be released when it is heated to flat-iron temperatures, so work in a ventilated room. It was developed as a safer alternative for hair smoothing treatments. Products using glyoxylic acid — including QIQI Hair Controller — are genuinely formaldehyde-free.
How long does glyoxylic acid treatment last?
Glyoxylic acid hair treatments typically last 3 to 5 months, depending on hair type, porosity, and aftercare. The treatment is semi-permanent — the new bonds formed by glyoxylic acid gradually relax over time with washing and environmental exposure. Using sulfate-free aftercare products and reducing wash frequency will help extend results.
Can glyoxylic acid damage hair?
When used correctly at formulated concentrations, glyoxylic acid is gentler on hair than both formaldehyde-based treatments and alkaline relaxers. Unlike relaxers, it does not permanently break the hair's disulfide bonds — it works alongside them, creating new bonds that reshape the hair without destroying its internal structure. However, excessive heat during application or using a product with inappropriately high concentrations could cause dryness or damage. Always follow the product instructions and use the correct flat iron temperature for your hair type.
Is glyoxylic acid safe during pregnancy?
There are no specific clinical studies on glyoxylic acid hair treatments during pregnancy. As with all chemical hair treatments, most dermatologists and obstetricians advise caution and recommend avoiding them during pregnancy as a general precaution. We are not medical professionals and cannot give medical advice — speak to your doctor or midwife before using any chemical hair treatment while pregnant or breastfeeding.
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Smooth hair. Honest ingredients.
QIQI Hair Controller — formaldehyde-free smoothing with glyoxylic acid at safe, tested concentrations. Dispatched next working day. UK delivery 1–3 working days.