Table 2

Summary of relevant characteristics of included studies

Studies	Publication year	Study design	Country	Sample size	Women (%)	Fitzpatrick skin type	Acne severity	Interventions	Main outcomes	Follow-up (weeks)
Abdel et al 10	2015	Single-centre, double-blind, split-face RCT.	Egypt	20	85	III, IV, V	Mild to moderate	25% TCA versus 30% SA (in hydroethanolic vehicle)	Percentage of total/good/fair/poor improvement in total lesions. Percentage of total/good/fair/poor improvement in non-inflammatory lesions. Percentage of total/good/fair/poor improvement in inflammatory lesions. Reduction of lesion counts. Adverse events.	10
Alba et al 11	2017	Single-centre, single-blind RCT.	Brazil	22	41	II, III, IV, VI	Mild to moderate	10% SA (in cream gel) versus phototherapy	Comedone counts. Papule counts. Pustule counts.	10
Bae et al 12	2013	Single-centre, single-blind, split-face RCT.	Korea	13	0	III or IV	Mild to moderate	30% SA versus JS	Number of non-inflammatory lesions. Number of inflammatory lesions. Self-reported good/moderate/mild/no improvement in all lesions. Adverse events.	8
Dayal et al 13	2017	Single-centre, single-blind RCT.	India	40	35	N/A	Mild to moderate	30% SA versus JS.	Comedone counts. Overall percentage decrease in mean comedone counts. Papule counts. Overall percentage decrease in mean papule counts. Pustule counts. Overall percentage decrease in mean pustule counts. MAS. Percentage decrease in mean MAS. Percentage of good/fair/poor response. Adverse events.	12
EI Refaei et al 14	2015	Single-centre, open-label RCT.	Egypt	40	80	I, II, III, IV	Mild to very severe	20% SA+10% MA (in ethyl alcohol vehicle) versus 35% GA (in distilled water)	Comedone counts. Papule counts. Pustule counts. Percentage of improvement in comedones/papules/pustules/the total acne score. Adverse events.	20
Ilknur et al 8	2010	Single-centre, single-blind, split-face RCT.	Turkey	30	N/A	II, III	Mild to moderate	GA (from 20% to 70%) versus AFA (from 20% to 60%)	Non-inflammatory lesion counts. Inflammatory lesion counts. Patients’ choice for future treatment. Adverse events.	24
Jaffary et al 15	2016	Multi-centre, single-blind RCT.	Iran	86	92	N/A	Mild to moderate	30% SA (in alcohol vehicle) versus 50% PA (in hydro alcoholic vehicle)	Comedone counts. Papule counts. Pustule counts. Percentage of excellent/good/fair/poor improvement of all lesions. Acne Severity Index. Percentage of patient satisfaction. Adverse events.	8
Kaminaka et al 16	2014	Single-centre, double-blind, split-face RCT.	Japan	25	64	N/A	Moderate to severe	40% GA versus placebo (hydrochloric acid in polyethylene glycol vehicle)	Non-inflammatory lesion counts. Inflammatory lesion counts. Total lesion counts. Percentage of excellent/good/fair/bad improvement in all lesions. Bioengineering measurements. Adverse events.	10
Kessler et al 19	2008	Single-centre, double-blind, split-face RCT.	USA	20	65	N/A	Mild to moderate	30% GA versus 30% SA	Mean number of all lesions. Reduction of all lesions. Percentage of good/fair/poor improvement in all lesions. Self-reported overall improvement. Adverse events.	20
Kim et al 20	1999	Single-centre, single-blind, split-face RCT.	Korea	26	84.6	III, IV	Mild to moderate	70% GA versus JS (resorcinol, salicylic acid, lactic acid in ethanol)	Percentage of patients who achieved improvement in acne scores of 0.5 or more. Self-reported overall improvement. Patients’ choice for future treatment. Adverse events.	8
Leheta21	2009	Single-centre, single-blind, RCT.	Egypt	45	N/A	II, III, IV	Mild to moderate	20% TCA versus PDL	Acne severity score. Mean remission period. Percentage of marked/moderate response. Self-reported cost-effectiveness ratio. Adverse events.	48
Levesque et al 9	2011	Single-centre, open-label, split-face RCT.	USA	20	95	N/A	N/A	LHA (5% or 10%) versus SA (20% or 30%)	Reduction of non-inflammatory lesions. Inflammatory lesion counts. Global acne assessment. Adverse events.	14

AFA, amino fruit acid; GA, glycolic acid; JS, Jessner’s solution; LHA, lipohydroxy acid; MA, mandelic acid; MAS, Michaelson Acne Score; N/A, not available; PA, pyruvic acid; PDL, pulsed dye laser; RCT, randomised controlled trial; SA, salicylic acid: TCA, trichloroacetic acid.