Kessler 2008.

Study characteristics
Methods	Aim of study: to compare the efficacy of alpha‐ and beta‐hydroxy acid chemical peels in the treatment of mild to moderately severe facial AV Design: split‐face, double‐blind, randomised, controlled study Unit of allocation: faces Allocation: randomisation; no details Blinding: double‐blind; but only assessors were blinded clearly Duration of trial (from recruitment to last follow‐up): not described Dropouts: 3
Participants	Population description: mild to moderately severe facial AV Setting: University School of Medicine, USA Randomised number: 20 Age: 24 (13 to 38) years Sex: 7/13 Severity of illness: mild to moderately severe
Interventions	Name of treatment group: glycolic acid; n = 20 faces Description: 30% glycolic acid (Glyderm, Valeant Pharmaceuticals Inc. Costa Mesa, CA, formerly ICN Pharmaceuticals Inc.) Treatment period: 10 weeks Timing: every 2 weeks; 4 to 5 minutes each treatment Name of treatment group: SA; n = 20 faces Description: 30% SA (B‐LIFTx, Bradley Pharmaceuticals, Inc., Fairfield, NJ, formerly Bioglan Pharmaceuticals) Treatment period: 10 weeks Timing: every 2 weeks; 4 to 5 minutes each treatment
Outcomes	Primary outcomes Participants' global self‐assessment of acne improvement (e.g. measured by a 4‐point scale: excellent, good, fair, and poor). Assessed by completing a questionnaire at the 1‐month post‐treatment follow‐up visit. Split‐face design Withdrawal for any reason. Three dropouts during the 10‐week treatment period; split‐face design Secondary outcomes Change in lesion counts (total or inflamed and non‐inflamed separately). Weeks 2, 4, 6, 8, 10 and post‐treatment follow‐up (weeks 14, and 18), no usable data Physicians' global evaluation of acne improvement. Five‐point system (good: more than 50% improvement, fair: 21% to 50% improvement, poor: 10% to 20% improvement, no change, or worse) assessed at the 1‐ and 2‐month post‐treatment follow‐up visits. Split‐face design Minor adverse events (assessed as total number of participants who experienced at least one minor adverse event). Authors reported this outcome but no data provided Quality of life (QoL). Authors did not report this outcome
Notes	Funding: not described
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Treatment sites were randomly assigned before the first treatment visit by assigning one side of the face to receive the 30% glycolic acid...". Comment: no details of random methods were described
Allocation concealment (selection bias)	Unclear risk	No details
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Although 'double‐blind' was mentioned, no details were reported for its identification.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "A blinded evaluator performed the quantitative and clinical assessment from baseline through the 2‐month follow‐up." Comment: blinding probably sufficient
Incomplete outcome data (attrition bias) All outcomes	Low risk	3 dropouts (15%) with reasons and ITT analysis was used
Selective reporting (reporting bias)	Unclear risk	Insufficient data regarding investigator and patient assessment of acne improvement
Other bias	Low risk	No other potential bias identified