Cyanocobalamin

Cyanocobalamin (vitamin B12) is typically used at very low concentrations in leave-on products (often around 0.001–0.1%) as a skin-conditioning/soothing additive and is generally well tolerated. However, there are documented cases of allergic contact dermatitis and rare hypersensitivity reactions to vitamin B12 derivatives, so it is not fully inert in highly reactive or eczematous populations. Given the low dose but nonzero sensitization potential, it fits best as very gentle rather than completely irritation-free. Safety Notes: In commercial skincare, cyanocobalamin (vitamin B12) is most often used as a trace-level color/marketing active in leave-on serums and creams, with many products effectively dosing in the ~0.000001–0.001% range. Higher-strength consumer-available products marketed for redness/eczema-prone skin (e.g., B12 creams/ointments and concentrated serums) commonly run ~0.01–0.05%, with the upper end constrained by intense coloration, staining risk, and diminishing formulation practicality rather than regulation. Rinse-off products tend to sit at the low end due to limited benefit-on-skin and cost/color considerations.