Four reported cases of acute renal failure following the application of so-called "Brazilian straightening" products containing glyoxylic acid, have led the French authorities — the National Agency for Food, Environmental and Occupational Health Safety (ANSES), the General Directorate for Competition, Consumer Affairs and Fraud Control (DGCCRF) and the General Directorate for Health (DGS) — to recommend not using them, as a matter of “precaution".

Four reported cases

The cases were reported between January and August 2024. The four people concerned were aged 28 to 42 and "recovered following treatment" in local hospitals, said France’s ANSES. The agency also said it has launched an expertise on the renal toxicity of glyoxylic acid when used in hair applications. Currently, the European cosmetics regulation does not restricts the use for this ingredient. Glyoxylic acid is often used as a substitute for formaldehyde, which has been classified as carcinogenic since 2013. Among other functions, glyoxylic acid allows the curling or straightening of hair.

The four French cases occurred after application of straightening products in a hair salon.

When glyoxylic acid "passes into the bloodstream through the scalp", it can "transform into calcium oxalate crystals", which will cause kidney damage, explained to AFP Dr. Juliette Bloch, director of health alerts and vigilance at the French agency.

"It is very likely that other cases have gone unreported: sometimes, drinking water will eliminate the crystals, so they will remain unnoticed. And even if there has been kidney failure diagnosed in the hours that follow, one may not make the connection," she continued. "The purpose of our alert is that people think about it."

Hair salons and individuals are therefore advised not to use these products and cosmetics stores are should not sell them, pending the conclusions of the ANSES expertise, which is expected to be released at the end of 2024.

In the event of signs of kidney failure - abdominal or lower back pain, nausea and/or vomiting - a few hours after applying a hair product containing glyoxylic acid, it is recommended to "consult a doctor quickly or call a poison control centre" and mention this use, warns the agency.

Scientific assessment

"About twenty cases have been reported in Israel in recent years, the same as what has been observed in France," said Sandrine Charles, cosmetics project manager at ANSES, "and one in Switzerland."

In June, the French Academy of Medicine recommended, in light of scientific articles, to "send warning and information messages to health professionals, hair salons and cosmetics stores." Insisting on "a health risk that could be underestimated, because it is unknown," the organisation stressed "the importance of not performing hair straightening in the event of scalp lesions, which increases the penetration of glyoxylic acid."

Despite "suspicions regarding the toxicity of glyoxylic acid", "current elements do not allow definitive conclusions to be drawn and remind the importance to follow the instructions and precautions for use" stated FEBEA, the French trade association representing cosmetic product manufacturers in France, on Wednesday, October 16.

According to FEBEA, it is important to only apply these products to a healthy scalp, without any lesions, and to seek help from a trained hairdressing professional.

French cosmetics giant L’Oréal, said AFP that it does not "add glyoxylic acid as an ingredient in any of its products, in any market in the world.”

Depending on its conclusions, the assessment undertaken by ANSES may lead France to propose an shift in the European regulatory texts governing cosmetic products.