Evidence-based topical treatments (azelaic acid, salicylic acid, nicotinamide, sulfur, zinc, and fruit acid) for acne: an abridged version of a Cochrane systematic review

Objective: The effects of topical azelaic acid, salicylic acid, nicotinamide, sulfur, zinc, and fruit acid (alpha-hydroxy acid) for acne are unclear. We aimed to assess the effects of these topical treatments by collecting randomized controlled trials. Methods: We searched The Cochrane Skin Group Specialised Register, CENTRAL, MEDLINE, Embase, and LILACS up to May 2019. We also searched five trials registers. Two review authors independently extracted data and assessed risk of bias. Meta analyses were performed by using Review Manager 5 software. Results: We included a total of 49 trials involving 3880 participants. In terms of treatment response (measured using participants’ global self-assessment of acne improvement, PGA), azelaic acid was probably less effective than benzoyl peroxide (RR = 0.82, 95% CI 0.72-0.95). However, there was probably little or no difference in PGA when comparing azelaic acid to tretinoin (RR = 0.94, 95% CI 0.78-1.14). There may be little or no difference when comparing salicylic acid to tretinoin (RR = 1.00, 95% CI 0.92-1.09). There were no studies measured PGA when evaluating nicotinamide. With respect to alpha-hydroxy acid, there may be no difference in PGA when comparing glycolic acid to salicylic-mandelic acid (RR = 1.06, 95% CI 0.88-1.26). We were uncertain about the effects of sulfur and zinc. Adverse events associated with these topical treatments were always mild and transient. Conclusions: Moderate-quality evidence was available for azelaic acid and low- to very-low-quality evidence for other topical treatments. Risk of bias and imprecision limit our confidence in the evidence.