Oway Hstraighten Smoothing Treatment: How It Works, and What the Research Says About Glyoxylic Acid

A clear-eyed look at the treatment, the science behind glyoxylic acid, and the risks and rewards — so you can decide for yourself.

Smoothing treatments promise something tempting: months of frizz-free, easy-to-style hair that holds up against humidity. The Oway Hstraighten Holistic Smoothing System is one of the cleaner-formulated options in this category, and it's one we get asked about often.

Rather than hand you a sales pitch, here's a straight look at how it works, what's in it, and what the current research actually says about its active ingredient — including the parts worth taking seriously.

What Hstraighten is

Hstraighten is a semi-permanent smoothing treatment. It's designed to reduce frizz, loosen wave and curl, add shine, and cut down styling time — with results that last, per Oway, roughly 3 to 5 months depending on hair type, technique, and home care. It is not a permanent chemical straightener or relaxer; it smooths and relaxes texture rather than forcing hair pin-straight.

Its active ingredient is glyoxylic acid, the same formaldehyde-free active used in most modern "Brazilian" smoothing treatments.

How glyoxylic acid works

Your hair's texture comes from how its keratin proteins and internal bonds are arranged. Glyoxylic acid changes that arrangement:

• It's an organic acid (an alpha-keto acid) that penetrates the hair fiber and reacts with sites on the keratin proteins, forming new cross-links that alter how the hair holds its shape. (SpecialChem INCI overview)

• These treatments work at a very low pH — below 2.0 — and, unlike alkaline relaxers, involve no neutralization step. Instead, a flat iron is applied repeatedly to activate the process and form a smoothing polymer film along the strand. (Impact of Acid vs. Alkaline Straightening, PMC)

• Heat is essential. The flat-iron step is what locks in the conformational change and seals the cuticle for that glassy, smooth finish. (Smoothing treatment science overview)

Oway describes the action as recomposing the electrostatic charges that bind the amino acids inside the hair, with the mechanical action of the iron letting those amino acids rearrange into a smoother, more compact surface. (Oway USA product page)

What's in the Oway formula specifically

Where Hstraighten distinguishes itself is the surrounding formula. Per Oway, it's 87.17% naturally derived, vegan, and free from SLS/SLES, parabens/MIT, synthetic fragrances, petrolatum, PEG-PPG, phthalates, and EDTA, and it's dermatologically and nickel tested. (Oway USA) It's built on a base of biodynamic dock root, organic mullein flower, and oils of date, coconut, and avocado. (full ingredient list here)

Worth noting: a cleaner supporting formula doesn't change how the active ingredient itself behaves. That's the part that deserves a careful look.

The rewards

• Real, lasting smoothness. Reduced frizz and loosened texture for several months, not days.

• Less daily heat. Many people cut significant time off their routine and, importantly, use hot tools far less often day-to-day — which matters, since routine flat-ironing is itself a source of cumulative hair damage.

• A gentler process than old-school straightening in some respects: it's formaldehyde-free as formulated, and works without the harsh alkaline chemistry of hydroxide relaxers.

The risks — what the research actually says

This is where honesty matters more than a sales pitch. There are two documented concerns with glyoxylic acid treatments as a category, and you deserve the real picture.

1. Formaldehyde release during the flat-iron step. "Formaldehyde-free" refers to what's in the bottle — not necessarily what comes off your hair under heat. Because glyoxylic acid contains an aldehyde group, research indicates it can release formaldehyde gas when heated to flat-iron temperatures, sometimes at levels exceeding recommended air limits in poorly ventilated spaces. (AKI case report discussing formaldehyde release, PMC; safety assessment measuring air release, ScienceDirect) This is a meaningful exposure consideration for both the client and — with repeated daily services — the stylist, and it's why ventilation and controlled iron temperatures matter.

2. An emerging link to acute kidney injury (AKI). This is the more serious finding, and it's newer. When absorbed through the skin, glyoxylic acid can be metabolized into oxalate, which can form calcium oxalate crystals in the kidneys:

• A mouse study found that topical glyoxylic acid dramatically increased urinary oxalate and caused calcium oxalate kidney damage after absorption through the skin. (ScienceDirect case series + mechanism)

• A 2023 case series identified 26 patients across 14 Israeli medical centers who developed severe AKI after glyoxylic-acid hair straightening. (same source)

• A 2025 case series (Clinical Toxicology) followed 13 patients; 12 developed acute kidney injury, with calcium oxalate crystals found in some. None required dialysis and there were no deaths, and early treatment appeared to reduce severity. (Clinical Toxicology, Tandfonline)

• A 2025 systematic review concluded that hair-straightening products containing formaldehyde, glycolic acid, or glyoxylic acid may be nephrotoxic. (PubMed)

• In late 2024, French health authority ANSES reviewed cases of AKI following these treatments and recommended caution while the risk is studied further. (Typology summary of ANSES report)

Some important context: these are case reports and small series, not large population studies, and the total number of documented cases is small relative to how many treatments are performed worldwide. The mechanism (skin absorption → oxalate → crystals) is biologically plausible and consistent across reports, but the full scope of risk — how often, at what dose, in whom — is still being established. Reported symptoms to watch for after a treatment include nausea, vomiting, and abdominal pain.

How this informs a responsible approach

If you're considering a glyoxylic acid smoothing treatment anywhere, these are reasonable, research-aligned precautions:

• Ventilation and controlled iron temperature during application, to limit formaldehyde exposure.

• Keeping product off the scalp and skin as much as possible, given the absorption-to-oxalate pathway.

• Not stacking treatments back-to-back or over-frequently.

• Sitting it out if you're pregnant or have any history of kidney issues — a sensible precaution while the research develops.

• Professional application over DIY, since technique directly affects exposure.

The bottom line

Hstraighten is one of the cleaner-formulated smoothing systems available, and for the right person it delivers months of genuinely easier hair. It's also true that its active ingredient, glyoxylic acid, carries documented risks — formaldehyde release under heat, and an emerging association with acute kidney injury — that the whole category is currently reckoning with.

Neither of those facts makes the decision for you. Our job is to give you the full picture and let you weigh it. If you'd like to talk it through for your specific hair and health situation — or explore gentler smoothing and frizz-management options that don't use glyoxylic acid at all — book a consultation and we'll have an honest conversation about what's actually right for you.

Rooted Organic Beauty is a clean beauty salon collective in Donelson, Nashville. @rootedorganictn

Sources

• Oway Hstraighten product page — pro.owayusa.com

• Glyoxylic Acid INCI overview — SpecialChem

• Impact of Acid vs. Alkaline Straightening on the Hair Fiber — PMC10075350

• Acute Kidney Injury and Hair-Straightening Products: A Case Series (+ mouse mechanism study) — ScienceDirect

• AKI Following Formaldehyde-Free Hair-Straightening Products (formaldehyde release discussion) — PMC9386411

• Hair straightening and acute kidney injury: a case series (2025), Clinical Toxicology — Tandfonline

• AKI induced by topical hair straightening products: a systematic review (2025) — PubMed

• Safety evaluation: formaldehyde release and oxalic acid formation (2025) — ScienceDirect

• ANSES caution guidance summary — Typology

• Full Hstraighten ingredient list — ireadlabelsforyou.com