Acute kidney injury induced by topical hair straightening products: A systematic review

BACKGROUND Hair straightening products containing formaldehyde, glycolic acid, and glyoxylic acid may be nephrotoxic, as several studies have reported acute kidney injury (AKI) induced by these chemicals. AIM To investigate the clinical features, complications, and treatment of AKI resulting from topical exposure to hair-straightening products. METHODS The study protocol was registered with PROSPERO under the registration number CRD420251010513. PubMed, Web of Science, and Scopus were searched from inception to April 3, 2025, for case reports and case series describing patients diagnosed with AKI-defined as an increase in serum creatinine of ≥ 0.3 mg/dL, following exposure to hair-straightening products. Means and standard deviations were used to describe continuous variables and frequencies and percentages were reported for dichotomous variables. RESULTS The search yielded 168 potentially relevant articles, of which six case reports and two case series met the inclusion criteria, collectively providing data on 34 patients for 36 incidents (in one case report, three AKI episodes occurred in the same patient). In 20 incidents, the hair product was identified as “formaldehyde-free”, while in 16 incidents, the chemical composition was unknown. All patients were female (mean age: 28.53 ± 11.72 years; range: 10-58 years) and the median time for the development of AKI was 2 days. The mean serum creatinine level at admission was 5.24 ± 2.83 mg/dL (range: 1.9-13.2 mg/dL). The most common presenting symptoms were vomiting (n = 29/36; 80.6%), nausea (n = 25/36; 69%), and abdominal pain (n = 13/36; 36%). Complications included one patient who developed severe dyspnea with bilateral lung infiltrates and another who developed severe hypertension and hyperkalemia. Twenty-one incidents were managed conservatively, five required steroid therapy, three required hemodialysis, and three required both hemodialysis and steroids. All patients recovered and were discharged. CONCLUSION The findings of this systematic review highlight the need for caution when using hair-straightening products due to their potential to cause AKI.