"Is this safe?" is the most important question you can ask before any hair-smoothing treatment — and it deserves an honest answer rather than a sales pitch. The short version: keratin treatments are not all the same, and the safety difference comes down mostly to one ingredient.
The real issue: formaldehyde
Some keratin and Brazilian-style smoothing products contain formaldehyde or formaldehyde-releasing chemicals such as methylene glycol. When the hair is heated with a flat iron, these can release formaldehyde gas into the air, which the client and stylist then breathe in.
This matters because formaldehyde is classified as a human carcinogen, and short-term exposure can irritate the eyes, nose, throat and skin (National Cancer Institute). The U.S. FDA has warned consumers that some hair-smoothing products can release formaldehyde during use (FDA).
Regulators are still catching up. The FDA has been working on a proposed rule to ban formaldehyde and formaldehyde-releasing chemicals in hair-smoothing products, but as of early 2026 it has repeatedly missed its own deadlines and the rule is not yet in force (CNN, January 2026). In other words: you can't assume a product is safe just because it's on sale — it's worth checking.
The good news: formaldehyde-free options
You don't have to choose between smooth hair and peace of mind. Modern formaldehyde-free treatments use gentler chemistry — for example amino-acid and glyoxylic-acid formulas, and nanoplasty, which is built on amino acids and collagen.
At OK Beauty Hair, the keratin and nanoplasty treatments we use are formaldehyde-free. One honest caveat worth knowing: independent testing has occasionally found formaldehyde in products labelled "formaldehyde-free", so the label alone isn't enough — the salon's knowledge of their products is what counts.
How to keep yourself safe — a checklist
- Ask what product is used and whether it's formaldehyde-free (look out for "formaldehyde", "methylene glycol", "formalin").
- Choose a ventilated salon with a trained stylist.
- Avoid smoke or eye/throat irritation during the service — that can be a sign of formaldehyde release.
- If you're pregnant or breastfeeding, it's sensible to postpone or choose a formaldehyde-free option, and check with your midwife or GP.
- Patch-test friendly: tell your stylist about allergies or a sensitive scalp.
Does keratin damage your hair?
Done properly, no. A keratin treatment coats and smooths the hair rather than stripping it. Damage, when it happens, usually comes from excessive heat or poor technique — which is exactly why an experienced specialist matters. For already-damaged hair, a hair reconstruction treatment beforehand can strengthen the hair first.
The bottom line
A keratin treatment can be a safe, transformative service — if you choose a formaldehyde-free product and a stylist who knows what they're using. Still weighing your options? Compare your choices in our guide to keratin vs hair botox vs nanoplasty, or book a consultation and we'll talk you through the safest option for your hair.
This article is general information, not medical advice. If you have specific health concerns, speak to your GP or midwife.
