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

Table 4 Quality of the included case reports and case series

Ref.	Was the exposure (hair-straightening products) adequately ascertained?1	Was the outcome (AKI) adequately ascertained?2	Were other alternative causes that may explain the outcome (AKI) ruled out?3	Were all important data cited?4	Risk of bias5
Abu-Amer et al[20], 2022	Yes	Yes	Yes	Yes	Low
Bashir and Khater[16], 2023	Yes	Yes	Yes	Yes	Low
Huber et al[15], 2024	Yes	Yes	Yes	Yes	Low
Mitler et al[18], 2021	Yes	Yes	Yes	Yes	Low
Robert et al[41], 2024	Yes	Yes	Yes	Yes	Low
Zergui et al[14], 2025	Yes	Yes	Yes	Yes	Low
Ahmed et al[17], 2019	Yes	Yes	Yes	Yes	Low
Bnaya et al[19], 2023	Yes	Yes	Yes	Yes	Low

¹Ascertainment of the exposure, i.e., hair straightening products: e.g., AKI developed during the 48-72 hours following hair-straightening product exposure, and the patient experienced systemic signs such as abdominal pain, vomiting, and scalp eruption/ irritation, etc. within 24 hours of hair-straightening product exposure.

²Ascertainment of the outcome (acute kidney injury), i.e., raised serum creatinine was demonstrated or a definition of acute kidney injury was used, e.g., acute kidney injury was defined according to Acute Kidney Injury Network criteria, etc.

³Causality: Other etiologies for acute kidney injury, such as viral, immune, and pharmacological, were excluded after clinical, laboratory, and immunological evaluation.

⁴Important data was defined as the history of use of hair straightening products, time from exposure, clinical signs and symptoms, serum creatinine at the time of admission, and outcome.

⁵Risk based on the responses of the first four questions (4 yes indicates low risk; 3 yes indicates moderate risk; 2 or less yes indicates high risk).

AKI: Acute kidney injury.