Glyoxylic Acid Hair Straightening: The Kidney Warning

ANSES¹ advises against using hair-straightening products containing glyoxylic acid after reports of acute kidney injury. The French health agency’s assessment identified a highly probable causal link, described in its May 2025 cosmetovigilance bulletin.¹

If you feel unwell after straightening

Unusual lower-back or abdominal pain, nausea, vomiting or marked tiredness after the procedure need prompt medical advice. ANSES’s¹ May 2025 account describes symptoms during application or in the following hours and advises seeing a doctor or contacting a poison control centre, mentioning the straightening treatment.¹

Luxembourg’s health guidance, updated in January 2026, also advises stopping the suspected cosmetic product and seeking medical advice as needed.² Tell the clinician when the treatment happened and when each symptom began. Request a photograph of the product label from the salon if you do not have it, but do not postpone care while waiting for the picture.

These symptoms have several possible causes. Mentioning the exposure helps the clinician decide what to investigate; it does not diagnose kidney injury from the timing alone.

What the human reports show

A 2025 Clinical Toxicology study³ reviewed 13 female patients evaluated at Sourasky Medical Center in Tel Aviv between April 2021 and March 2025 after symptoms followed exposure to glyoxylic-acid-containing straightening products. Their mean age was 22. Twelve developed acute kidney injury. All received intravenous fluids; none required dialysis and none died.³

This was a small retrospective case series from a medical toxicology service. It examined patients who became symptomatic, rather than following everyone receiving the salon treatment. Twelve out of thirteen is not the risk for salon customers. The study cannot provide that population-wide rate or prove that any particular treatment prevents the injury.³

Why the ingredient raised concern

In a 2024 Kidney International experiment, researchers applied four preparations to separate groups of mice: a straightening product, a cream containing 10% glyoxylic acid, a cream containing 10% glycolic acid, or a control cream. The straightening product and glyoxylic-acid cream caused markedly increased urinary oxalate and calcium oxalate kidney injury.⁴

This supports a possible pathway involving absorption through skin and conversion to oxalate, which can form crystals. It is animal evidence about a mechanism, not a test of a safe salon concentration or an estimate of how often people are harmed. Glyoxylic acid and glycolic acid are different substances; the experiment does not justify treating their names as interchangeable.⁴

Ask for the ingredient list before booking

Look for Glyoxylic Acid on the product’s ingredient list. Luxembourg’s health guidance specifically identifies label checking as a way to establish whether it is present.² Get information for the product the salon will actually apply, including any substitute proposed on the day.

A practical request is: “Please send me the product name and full ingredient list before I confirm the appointment. Does this formulation contain glyoxylic acid?” If the salon cannot supply the details, leave the ingredient question unresolved rather than guessing from the service name.

The European Commission⁵ requested an SCCS safety assessment in a mandate approved on 30 April 2026. That document asks whether the ingredient is safe in straightening products and at what concentration; the request itself is not a finding of safety.⁵

The “Your Hair Log” section in Hair, Everywhere includes dated entries for products and styling changes. Keep the treatment date and exact product details there for future conversations. New symptoms after a procedure should be assessed promptly, without waiting to complete a hair-tracking period.