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

Table 1 Characteristics of the included case reports and case series

Ref.	Study type	Patient’s age/gender	Comorbidities	Clinical features	Serum creatinine (mg/dL)	Renal sonography	Renal biopsy	Treatment	Outcome	Hair straightening method
Abu-Amer et al[20], 2022	Case report	41/F	Hypothyroidism, sleeve gastrectomy	Weakness, nausea, vomiting	3.46	Yes	Yes	Prednisolone 1 mg/kg	Recovered. creatinine 0.9 after one week	Formaldehyde-free product
Bashir and Khater[16], 2023	Case report	40/F	Hypothyroidism	Scalp rash, hypertension, hyperkalemia	3.5	No	Yes	Pulse steroids	Recovered. Creatinine 0.9 at 4-month follow-up	Formaldehyde-free product
Huber et al[15], 2024	Case report	42/F	Healthy	Weakness, nausea, vomiting, flank pain, diarrhea, flank tenderness, hypertension	6.61	Yes	Yes	Conservative management	Recovered. Creatinine 0.87 at 3-month follow-up	Unknown
Mitler et al[18], 2021	Case report	13/F	Healthy	Abdominal pain, nausea, vomiting, oliguria, tachycardia, hypertension, dehydration, abdominal tenderness	3.56	Yes	Yes	Hemodialysis for four consecutive days	Recovered. Creatinine normalized 6-month follow-up	Formaldehyde-free product
Robert et al[41], 2024	Case report incidence 1	26/F	Healthy	Scalp burning sensation, scalp ulcers, vomiting, diarrhea, fever, back pain	2.1	Yes	No	Unknown	Recovered. Serum creatinine returned to normal (0.78) at the last follow-up	Containing 10% glyoxylic acid but no glycolic acid
	Incidence 2	25/F		Scalp burning sensation, scalp ulcers, vomiting, diarrhea, fever, back pain	2.4	Yes	No	Unknown	Recovered. Serum creatinine returned to normal (0.78) at the last follow-up	Formaldehyde-free product (containing 10% glyoxylic acid but no glycolic acid)
	Incidence 3	24/F		Scalp burning sensation, scalp ulcers, vomiting, diarrhea, fever, back pain	1.9	Yes	No	Unknown	Recovered. Serum creatinine returned to normal (0.78) at the last follow-up	Formaldehyde-free product (containing 10% glyoxylic acid but no glycolic acid)
Zergui et al[14], 2025	Case report	25/F		Nausea, vomiting, weakness	3.2	Yes	No	Saline, calcium gluconate, insulin, 25 g glucose, sodium bicarbonate	Recovered. Serum creatinine returned to 1.2 at the two-week follow-up	Formaldehyde-free product (contained glyoxylic acid)
Ahmed et al[17], 2019	Case series of 2 cases case 1	10/F	Healthy	Vomiting, tachycardia, dyspnea, hypertension, scalp rash	13.2	Yes	Yes	Hemodialysis for three consecutive days; 20 mg/kg/dose methylprednisolone for three days followed by oral prednisone (60 mg/m2/day)	Recovered. Discharged with improved RFTs	Formaldehyde-free product
	Case 2	17/F	Healthy	Vomiting, syncope, scalp rash	9.9	Yes	Yes	Hemodialysis for three consecutive days; corticosteroids 40 mg/day	Recovered. Discharged with normal RFTs	Formaldehyde-free product
Bnaya et al[19], 20231	Case series of 26 cases case 1	24/F	Healthy	Abdominal pain, nausea	5.82	No	No	No KRT, no steroids	Recovered	Unknown
	Case 2	22/F	Healthy	Abdominal pain, nausea, vomiting, scalp rash	2.76	No	No	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 3	30/F	Nephrolithiasis	Nausea, vomiting, scalp rash, flank pain	4.81	No	No	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 4	29/F	Healthy	Nausea, vomiting, scalp rash	2.09	No	No	No KRT, no steroids	Recovered	Unknown
	Case 5	21/F	Epilepsy	Abdominal pain, vomiting, scalp rash, headache	11.83	No	Yes	Steroids	Recovered	Unknown
	Case 6	58/F	Healthy	Nausea, flank pain, syncope	7.54	No	Yes	Steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 7	14/F	Healthy	Nausea, flank pain, headache	3.8	No	No	No KRT, no steroids	Recovered	Unknown
	Case 8	31/F	Healthy, smoking	Abdominal pain, vomiting, diarrhea	8.14	No	No	Temporary hemodialysis	Recovered	Unknown
	Case 9	29/F	Nephrolithiasis	Vomiting, scalp rash	6.8	No	No	No KRT, no steroids	Recovered	Unknown
	Case 10	52/F	Psoriasis, nephrolithiasis	Abdominal pain, flank pain, nausea, vomiting	3.4	No	No	No KRT, no steroids	Recovered	Unknown
	Case 11	24/F	Healthy	Abdominal pain, nausea, fever	2.17	No	No	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 12	33/F	Healthy	Nausea, vomiting, chills	6	No	No	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 13	13/F	Healthy	Abdominal pain, nausea, vomiting	3.56	No	Yes	Temporary hemodialysis	Recovered	Unknown
	Case 14	17/F	Psoriasis	Abdominal pain, nausea, vomiting	7.1	No	Yes	Temporary hemodialysis and steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 15	17.5/F	Healthy	Abdominal pain, nausea, vomiting, fever, scalp rash	2.9	No	No	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 16	24/F	Healthy	Abdominal pain, nausea, vomiting, scalp rash	4.2	No	No	No KRT, no steroids	Recovered	Unknown
	Case 17	36/F	Healthy	Nausea, vomiting, scalp rash	6	No	No	No KRT, no steroids	Recovered	Unknown
	Case 18	21/F	Healthy	Abdominal pain, nausea, vomiting	3.2	No	No	No KRT, no steroids	Recovered	Unknown
	Case 19	41/F	Hypothyroidism, sleeve gastrectomy	Nausea, vomiting	3.46	No	Yes	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 20	19/F	Healthy	Nausea, flank pain, headache	5.09	No	Yes	Steroids	Recovered	Unknown
	Case 21	44/F	Hypercoagulability state (prothrombin variant)	Vomiting, flank pain	7.8	No	No	No KRT, no steroids	Recovered	Unknown
	Case 22	50/F	Healthy	Nausea, vomiting	7.3	No	No	No KRT, no steroids	Recovered	Unknown
	Case 23	21/F	Healthy	Nausea, vomiting, flank pain, scalp rash	3.68	No	No	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 24	28/F	Atopic dermatitis, gastroesophageal reflux disease	Nausea, vomiting, flank pain, scalp rash	2.83	No	No	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 25	32/F	Healthy	Abdominal pain, nausea, vomiting	9.03	No	Yes	No KRT, no steroids	Recovered	Formaldehyde-free product (containing glycolic acid)
	Case 26	30/F	Healthy	Flank pain	7.36	No	No	No KRT, no steroids	Recovered	Unknown

¹In the case series of Bnaya et al[19], 2023, analyses of hair-straightening products marketed in Israel revealed varying concentrations of glyoxylic acid (range: 0.56%-17.9%) in some of the products. Ethylene glycol and diethylene glycol were not detected. The concentration of formaldehyde was < 200 ppm in most tested products.

KRT: Kidney replacement therapy; F: Female; RFT: Renal function tests.

Table 2 Renal ultrasonography findings of included studies

Ref.	Sonography findings
Abu-Amer et al[20], 2022	14.4-cm bilateral echogenic, edematous renal parenchyma
Huber et al[15], 2024	Normal kidneys with slight corticomedullary dedifferentiation, absence of pyelocaliceal dilation, and normal vascular flow
Mitler et al[18], 2021	15-cm edematous renal parenchyma
Robert et al[41], 2024 (3 incidents in the same patient)	No evidence of obstructive uropathy
Zergui et al[14], 2025	Normal-sized kidneys; findings consistent with acute kidney injury of non-obstructive etiology
Ahmed et al[17], 2019 (case 1)	Bilateral grade 1 nephropathy
Ahmed et al[17], 2019 (case 2)	Bilateral grade 1 nephropathy

Table 3 Renal biopsy findings of included studies

Ref.	Microscopic findings
Abu-Amer et al[20], 2022	The biopsy demonstrated features of both oxalate nephropathy and interstitial nephritis (intratubular oxalate crystals, interstitial edema, mixed inflammatory infiltrates with eosinophils, and foci of tubulitis)
Bashir and Khater[16], 2023	Acute interstitial nephritis
Huber et al[15], 2024	Findings were consistent with oxalate nephropathy rather than interstitial nephritis (numerous intratubular calcium oxalate crystal deposits and mild interstitial edema without inflammatory infiltrates)
Mitler et al[18], 2021	Oxalate nephropathy (microcalcifications/calcium oxalate crystals)
Ahmed et al[17], 2019 (case 1)	Acute tubulointerstitial nephritis
Ahmed et al[17], 2019 (case 2)	Acute tubulointerstitial nephritis
Bnaya et al[19], 2023 (case 5)	The biopsy demonstrated features of both oxalate nephropathy and interstitial nephritis (calcium oxalate crystals, small mononuclear interstitial infiltrate with spare eosinophils)
Bnaya et al[19], 2023 (case 6)	The biopsy demonstrated features of both oxalate nephropathy and interstitial nephritis (oxalate crystals, small mononuclear interstitial infiltrate)
Bnaya et al[19], 2023 (case 13)	The biopsy demonstrated oxalate nephropathy (microcalcifications/calcium oxalate crystals)
Bnaya et al[19], 2023 (case 14)	Oxalate nephropathy
Bnaya et al[19], 2023 (case 19)	The biopsy demonstrated features of both oxalate nephropathy and interstitial nephritis (oxalate crystals, multifocal mixed inflammatory infiltrates with multiple eosinophils)
Bnaya et al[19], 2023 (case 20)	Findings were consistent with oxalate nephropathy rather than interstitial nephritis (calcium oxalate crystals; interstitium with mild edema and sparse eosinophils)
Bnaya et al[19], 2023 (case 25)	Oxalate nephropathy

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.