Summary of findings 4. Chemical peeling versus placebo or no treatment for acne scars.

Chemical peeling versus placebo or no treatment for acne scars
Patient or population: people with acne scars Settings: out‐patient Intervention: chemical peeling versus placebo or no treatment
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No of Participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Control	Chemical peeling versus placebo or no treatment
Participant‐reported scar improvement (long‐term)	See comment	See comment	Not estimable	‐	See comment	This outcome was not measured
Participant‐reported scar improvement (short‐term)	See comment	See comment	Not estimable	‐	See comment	This outcome was not measured
Investigator‐assessed adverse events (short‐term)	See comment	See comment	Not estimable	‐	See comment	This outcome was not measured
Participant‐assessed adverse events (short‐term)	See comment	See comment	Not estimable	‐	See comment	Burning sensation and deep erythema were reported following frosting in some cases from the chemical peeling
Participant satisfaction	See comment	See comment	Not estimable	‐	See comment	This outcome was not measured
Quality of life	See comment	See comment	Not estimable	‐	See comment	This outcome was not measured
Serious or severe adverse events N of participants with positive severe adverse events Follow‐up: mean 6 months	0 per 1000	0 per 1000 (0 to 0)	RR 5.45 (0.33 to 90.14)	58 (1 study)	⊕⊝⊝⊝ very low1,2	7/43 participants experienced serious adverse events with chemical peel but 0/15 in the placebo group
*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; RR: Risk ratio;
GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate.

¹Downgraded one level for high risk of attrition bias.
 ²Downgraded two levels for very serious imprecision because the optimal information size (OIS) is far from met, extremely wide CI, due to low occurrence of events in control group and small sample size. 95% CI around the estimate of effect includes both no effect and appreciable harm.