Arginine/Lysine Polypeptide

Arginine/Lysine Polypeptide is a small cationic peptide used mainly for conditioning/skin feel and is typically present at low concentrations (often well under 1%). Peptides of this type are generally well-tolerated in clinical and consumer use, with irritation reports uncommon; however, their positive charge can occasionally sting or feel reactive on severely compromised barriers (e.g., active eczema or post-procedure skin). Given the low but non-zero potential for transient stinging in highly sensitive populations, it fits best as very gentle rather than exceptionally gentle. Safety Notes: In commercial skincare, arginine/lysine polypeptides are most commonly used as signal/conditioning peptides in leave-on serums, eye products, and moisturizers at trace-to-low levels (often ~0.0005–0.05%) due to cost and the fact that many suppliers recommend very low use levels for efficacy and stability. The upper end observed in consumer-available “peptide concentrate” serums and ampoules reaches about 0.5% active, beyond which solubility, tack/film feel, and overall formula stability typically become limiting. Rinse-off products generally sit at the low end because of short contact time, while high-strength positioning is predominantly in leave-on treatments.