Pentapeptide-59

Pentapeptide-59 is a synthetic signal peptide used in anti-aging formulas at very low concentrations (typically well below 0.1–0.5%), where it is not pH-dependent and does not act as an exfoliant or irritant active. Available cosmetic safety experience for peptides suggests low rates of irritation in standard patch testing, with most reactions attributable to the overall formula rather than the peptide itself. For highly reactive or eczematous skin there remains a small risk of stinging or rare sensitization, so it is best classified as very gentle rather than inert. Safety Notes: Pentapeptide-59 is a specialty cosmetic signal peptide typically supplied as a diluted solution in carriers (e.g., water/glycerin/butylene glycol), so finished-product use levels are generally in the ppm-to-low-bps range. In mass-market leave-on serums/creams it is often present at ~0.0001–0.001% active to support marketing claims while managing cost and stability; the highest OTC consumer “high-strength” peptide serums observed reach about 0.01% active, above which stability/solubility and supplier-recommended limits generally constrain real-world formulations. It is overwhelmingly used in leave-on products; rinse-off usage is uncommon and tends to stay at the low end due to short contact time.