Researchers warn glyoxylic and glycolic acid in hair straighteners may cause kidney injury

08 Apr 2024 --- A letter in The New England Journal of Medicine warns of “recurrent episodes of acute kidney injury” after a 26-year-old woman underwent hair-straightening procedures three times over the last two years and developed kidney damage.

Doctors claim it is apparently due to her salon visits, with evidence pointing to a chemical cream containing glyoxylic acid.

Oxalate nephropathy is noted as the type of kidney damage often caused by the accumulation of oxalate crystals. The woman’s doctors believe the use of the active ingredient caused her organ injuries. Additionally, they note she suffered from scalp burns and ulcerations due to the hair-straightening treatment. 

After experiments on mice, the doctors concluded the glyoxylic acid passed through her skin and into her kidneys, where it was broken down, causing damage.

Mounting evidence
Recent research in the American Journal of Kidney Diseases addresses the popularity of keratin-based hair-straightening treatments, the majority of which contain glycolic acid derivatives that are typically safe when used topically. 

The suggested mechanism of acute kidney injury following hair-straightening treatment (Image credit: American Journal of Kidney Diseases).“Systemic absorption of these products is possible, and anecdotal reports have described kidney toxicity associated with their use. We report a series of cases of severe acute kidney injury (AKI) following the use of hair-straightening treatment in Israel during the past several years,” warns the study.

“The most common symptoms at presentation were nausea, vomiting and abdominal pain. Scalp rash was noted in ten (38%) patients. Two patients experienced a recurrent episode of AKI following a repeat hair-straightening treatment. Seven patients underwent kidney biopsies… Three patients required temporary dialysis.”

The most common finding in kidney biopsies was acute oxalate nephropathy, which may be connected to the absorption of glycolic acid derivatives and their metabolism to oxalate, as noted by the authors.

Forbidden formaldehyde
According to researchers, another issue is the possible release of formaldehyde from products with high glycolic acid concentrations when these agents are heated to high temperatures According to researchers, another issue is the possible release of formaldehyde from products with high glycolic acid concentrations when these agents are heated to high temperatures.

“In Israel, the use of heating with these products is forbidden. In the past, formaldehyde was commonly used in hair-straightening products because it promotes cross-linking of hydrolyzed keratin solution to the hair fiber keratin. However, because of its toxic effects, the use of formaldehyde was banned by several countries, and others limited the maximum permitted concentration in cosmetic products,” detail the authors.

“However, formaldehyde is a carcinogenic and teratogenic agent, and acute exposure may result in skin lesions, headaches, eye irritation and injury to the respiratory tract. Thus, it has been banned in Brazil, Canada and the EU as an active ingredient in straightening products.”

Despite the ban, the EU recently found formaldehyde in 30% of cosmetic products. Last year, the US FDA proposed banning formaldehyde use in hair straightening products.

The authors explain that the restrictions caused a rise in the use of glycolic acid derivatives in hair-straightening products, often marketed as “formaldehyde-free.” However, according to their research, “glycolic acid derivatives may also release formaldehyde when exposed to high temperatures.”

“Although we cannot exclude formaldehyde as a potential nephrotoxic component contributing to AKI in our patients, the consistent finding of calcium oxalate deposition in kidney biopsies suggests the metabolism of glycolic acid derivatives to oxalate as the main mechanism of nephrotoxicity in our cases.”

“Tip of the iceberg”
The study presents its limitations due to a small number of kidney biopsies and a lack of information on the concentrations of glycolic acid derivatives and the pH of the products.

“It should also be noted that because there is no clear information regarding the total number of people undergoing hair straightening in Israel, a clear incidence cannot be established. Finally, because the follow-up period was relatively short and the number of patients was limited, we could not identify patient characteristics or clinical features associated with more severe presentation, slower recovery or need for dialysis,” write the authors.

By Venya Patel