Randomized, double-blinded, placebo-controlled clinical safety evaluation of a facial brightening toner containing niacinamide and β-arbutin used with 4% hydroquinone

Background Hydroquinone (HQ) remains the gold standard for treating facial hyperpigmentation, but irritation concerns may limit its use. β-arbutin and niacinamide are widely used cosmetic brightening ingredients; however, concerns that β-arbutin may release HQ have led to recommendations against combining β-arbutin-containing products with HQ. Clinical evidence evaluating the tolerability of this combination is limited.Objectives Assess the safety of a Facial Brightening Toner containing 3% niacinamide and 2% β-arbutin when combined with 4% HQ.Methods An 18-week randomized, double-blind, placebo-controlled study was conducted in adult female volunteers with facial hyperpigmentation and/or melasma. Volunteers received either a facial Brightening Toner or a Placebo Toner for 18 weeks, with 4% HQ through Week 10; they continued toner use through Week 18 without HQ. Assessments were performed at Baseline, Week 10, and Week 18, including facial erythema by a* measurements, VISIA CR red feature analysis, and adverse events monitoring.Results Forty-seven volunteers completed the study (Brightening Toner n = 23; Placebo Toner n = 24). Within-group and between-group analyses showed no significant changes in a* values from Baseline to Week 10, Baseline to Week 18, or Week 10 to Week 18 in either group, nor differences at any time point. Red feature analysis supported these findings. No irritation-related adverse events were reported.Conclusions A Facial Brightening Toner containing 3% niacinamide and 2% β-arbutin was well tolerated when combined with 4% HQ. These findings offer preliminary clinical safety evidence supporting the tolerability of β-arbutin- and niacinamide-containing cosmetic products used to support HQ therapy.