The observation was made by a team of French researchers who tested a suspected straightening product on animals. The substance investigated was glyoxylic acid which has replaced the banned formaldehyde in many hair straightening products.
This investigation was done in response to a healthy 26 yr old woman who had 3 episodes of acute kidney disease 1 year apart. She was using a hair product (cream) that contained glyoxylic acid. The patient reported feeling a burning sensation during the hair treatment. Scalp irritations appeared. She then experienced vomiting, diarrhea, fever, and back pain. Analyses revealed high levels of plasma creatinine during each episode, indicating renal failure.
They then carried out this research on mice and found that oxalate crystals were formed inside the kidneys when glyoxylic acid was applied topically.
Given the potential nephrotoxicity of glyoxylic acid through topical application, products containing this compound should be avoided and ideally withdrawn from the market, the researchers suggested in a letter published in The New England Journal of Medicine.
One should not confuse gyloxylic acid with glycolic acid (which is safe).