Long-term administration of conventional acne medications implies the potential risk of increasing microbial resistance, and safety risks. Recent interest has grown in probiotics as a potential treatment and as an adjunct for acne vulgaris.

To conduct a systematic review of randomized controlled trials of oral probiotics in reducing the severity of acne vulgaris compared to placebo or conventional treatments.

PubMed, Cochrane Central Register of Controlled Trials, Embase, WHO ICTRP and ClinicalTrials.gov were searched for relevant studies, and randomized controlled trials of acne vulgaris treatment with probiotic therapy were included. Outcomes include decrease in total lesion count/percent change from baseline, improvement of severity scores, inflammation related indicators, and gene expression. Changes in outcomes were calculated by effect size or pooled odds ratio.

A total of 2 RCTs involving 100 participants were included. Both studies show low risk on the risk bias criteria. The data of 2 RCTs reporting severity scores (AGSS and GAGS) supports that probiotics can improve their scores and thereby their condition. For inflammation-related indicators, only 1 RCT showed that probiotics can improve the IGF1 and FOXO1 gene expression in the skin. Regarding safety, only Eguren et al. reported adverse event. Their RCT showed that the incidence of adverse events was low and no serious adverse events.

In conclusion, the probiotics investigated in both studies may be given as adjuvant treatment for acne vulgaris as they improve the clinical course of patients.