Hair-straightening cosmetics containing glyoxylic acid induce crystalline nephropathy.

We recently reported the case of a patient who experienced three consecutive episodes of acute kidney injury, all of them following a "Brazilian" hair-straightening treatment. The cream used for the straightening procedure contained glyoxylic acid. To examine possible underlying mechanisms causing kidney injury, four groups of mice were exposed to topical application of (i) the straightening product, (ii) a cream containing 10% glyoxylic acid, (iii) a cream containing 10% glycolic acid or (iv) a control cream. Application of glycolic acid slightly increased urine oxalate excretion, while glyoxylic acid and the straightening product dramatically increased urine oxalate excretion and caused calcium oxalate nephropathy after transcutaneous absorption. Thus, glyoxylic acid was presumptively absorbed through the skin, metabolized to oxalate and promoted crystallization of calcium oxalate in urine. Hence, cosmetic products containing glyoxylic acid may induce acute kidney injury and should be discontinued. Further studies are needed to investigate the metabolism of glycolic acid and glyoxylic acid following topical application.