Veiga 2009.

Methods	RCT. Power calculation: no. Follow‐up period: 30 days.
Participants	Adult patients, scheduled for plastic surgery at a University‐affiliated hospital in Brazil. Exclusions: hypersensitivity to chlorhexidine, presence of skin lesions, antibiotic use at time of surgery, diabetes, heavy smoking, immunosuppression.
Interventions	Group 1: shower with liquid‐based detergent containing 4% chlorhexidine; Group 2: shower with the same liquid‐based detergent, without chlorhexidine; Group 3: no preoperative showering instructions were given. Patients in Groups 1 and 2 were asked to rinse thoroughly, lather with the antiseptic, rinse, lather and rinse again.
Outcomes	Primary outcome: Surgical site infection (defined using Centers for Disease Control criteria for wound infection and wound classification) Group 1: 1/50 (2%); Group 2: 1/50 (2%); Group 3: 0/50 (0%). Secondary outcome: Adverse reactions: no adverse reactions were reported.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated.
Allocation concealment (selection bias)	Unclear risk	Not described.
Blinding (performance bias and detection bias) Investigator and participant	Low risk	Surgeons and patients were all blinded to the allocation group.
Blinding (performance bias and detection bias) Outcome assessor	Low risk	Outcome assessors and microbiologists were all blinded to the allocation group.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All patients were followed for the nominated 30 days.
Selective reporting (reporting bias)	Low risk	Expected outcomes were reported.
Other bias	Low risk	The placebo solution was provided by Rioquimica Industria Farmaceutica, the manufacturer of the intervention product. However, as results in different groups were similar, this is unlikely to have affected results.