Keratin Treatment Safety: What to Ask Before You Book

Keratin treatments smooth the hair cuticle and reduce frizz for months, and they can be genuinely transformative for the right candidate. But the ingredient list matters enormously. Some formulas contain formaldehyde or formaldehyde-releasing chemicals that have real health implications. Others use safer alternatives. Asking what's in the formula before you book is not an overreaction. It's the right question.

A Complicated Reputation, and For Good Reason

Keratin treatments have a complicated reputation, and for good reason. Some are genuinely transformative. Some contain things that shouldn't go near your scalp. The range of formulas marketed as "keratin treatments" is wide enough that two treatments with the same name can have almost nothing in common beyond the marketing language. Our team has been navigating this on behalf of clients from across the GTA for years, and the most useful thing we can do is give you an honest picture of what these treatments actually are, what the chemical differences mean, and how to ask the right questions before committing to one.

What a Keratin Treatment Actually Does

Keratin treatments work by depositing a protein layer (typically a keratin or keratin-like compound) around the hair cuticle and sealing it flat. This coating smooths the cuticle surface, reduces the amount of moisture the hair absorbs from the air (the main driver of frizz), and creates a temporary shield around the shaft. The results last anywhere from six weeks to six months depending on the formula strength, your hair type, and how you maintain the treatment. Most keratin treatments also use heat (a flat iron applied at high temperature) to bond the protein layer to the cuticle. The chemical that completes that bonding process, or is a byproduct of the heat activation, is where the safety question lies.

The Formaldehyde Question

Formaldehyde is a known carcinogen. Many keratin treatments, particularly older formulations and some imported products, either contain formaldehyde directly or contain formaldehyde-releasing compounds such as methylene glycol, which releases formaldehyde gas when heated. Health Canada has flagged these concerns, and salon workers who apply formaldehyde-based treatments regularly face the highest occupational exposure risk. For clients, a single treatment in a well-ventilated space carries significantly lower risk than repeated occupational exposure, but the risk is not zero. Here's the counterintuitive part: formaldehyde-based treatments tend to produce longer-lasting and more dramatically smooth results than formaldehyde-free alternatives. That's part of why they've persisted in some salons despite the health concerns. The trade-off is real.

Safer Alternatives: Glyoxylic Acid and Others

The most common formaldehyde-free alternative uses glyoxylic acid, which bonds to the keratin in the hair and smooths the cuticle without releasing formaldehyde gas. Results are generally softer and shorter-lived than formaldehyde-based treatments, typically three to four months rather than five to six, but the safety profile is meaningfully better. Other formulations use cysteine (an amino acid), propylene glycol, or plant-based keratin proteins. At Backstage, we use formaldehyde-free formulations exclusively. The results we get with glyoxylic acid-based treatments are excellent for the right candidate: natural hair texture, significantly reduced frizz, smoothness that lasts. And we're not willing to expose our clients or our team to formaldehyde gas to chase a marginally longer result.

Who Benefits Most, and Who Should Pause

Keratin treatments work best on hair that is naturally frizzy, wavy, or coarse and struggles with humidity, a relevant concern across GTA summers. They work well on colour-treated hair as long as the hair is not severely damaged. They are not appropriate for very fine hair, where the coating can weigh fine strands down and reduce rather than add volume. They're also not recommended during pregnancy. If you colour your hair, timing matters: keratin treatments should go on before colouring or at least two weeks after, and the sulphate-free shampoo required after a keratin treatment will fade your colour faster than regular maintenance. A consultation before booking helps us assess whether your hair is a good candidate and set accurate expectations.