Riboflavin

Riboflavin (vitamin B2) is primarily used as a colorant/antioxidant-support ingredient in low concentrations and is generally well tolerated in topical products. Clinical and consumer patch-test data suggest a very low rate of irritation or sensitization, with reactions being uncommon and typically limited to highly reactive or compromised skin. Given the need to account for sensitive-skin populations while recognizing its overall benign profile, it fits best as exceptionally gentle rather than fully inert. Safety Notes: In commercial skincare, riboflavin (vitamin B2) is most often used as a minor skin-conditioning/antioxidant component or naturally present in “vitamin blends,” commonly appearing around ~0.0001–0.01% in leave-on creams/serums where color and photoinstability limit higher use. Higher-strength consumer products (typically leave-on serums/ampoules or multi-B-vitamin treatments) can reach ~0.1–0.5% when formulators accept strong yellow coloration and manage light/oxygen exposure with protective packaging; rinse-off products generally sit at the lower end because benefits are harder to justify versus stability and staining risk. No specific EU/FDA cosmetic concentration cap is generally applied for riboflavin, so practical formulation constraints (intense color, light sensitivity, potential staining) define the observed market maximum.