Acetyl Tetrapeptide-2

Acetyl Tetrapeptide-2 is a synthetic signaling peptide used in low concentrations (typically well under 1%) for firming/anti-aging, and peptides as a class are generally non-stinging and well-tolerated in clinical use. Reported irritation and sensitization rates are low compared with acids, retinoids, or fragrance allergens, but any leave-on ingredient can trigger reactivity in highly compromised eczema skin, so it is best categorized as very gentle rather than inert. Safety Notes: In consumer leave-on anti-aging products (serums, eye creams, and firming moisturizers), Acetyl Tetrapeptide-2 is most often present at very low active levels because it is typically supplied as a dilute solution (often ~0.5–5% active in glycerin/water) and used at low inclusion rates; this yields finished-product actives around 0.0001–0.001% at the gentle/low end. High-strength OTC “peptide concentrate” serums and multi-peptide boosters occasionally push the finished active level up to about 0.01% when using higher supplier-recommended maximums and/or more concentrated peptide raw materials, but higher levels are uncommon due to cost, diminishing returns, and stability/formulation constraints; it is rarely used in rinse-off formats and is primarily a leave-on active.