A technical guide to Tetrapeptide-21 identity, delivery, serum formulation, stability and cosmetic claim support. Written for cosmetic brands, formulators, distributors and professional B2B buyers.
What Tetrapeptide-21 means
Tetrapeptide-21 is a four-amino-acid cosmetic peptide also discussed by the sequence shorthand GEKG. It appears in firming and age-support concepts, but the INCI name alone does not disclose purity, counterion, carrier system or commercial concentration. Buyers should start with the exact grade rather than a generic ingredient description.
Powder, solution or delivery system
Tetrapeptide-21 may be offered as dry material, an aqueous stock solution or within a more complex carrier. Dry material offers control but requires accurate low-dose handling and dissolution. A stock solution simplifies dosing while contributing water, glycols and possibly preservatives. Advanced delivery research cannot be assumed to describe a conventional serum.
Active-content basis
A supplier-solution percentage is not the percentage of pure GEKG peptide. Request the active fraction, assay definition and complete INCI composition. Calculate nominal finished-formula peptide content separately from the raw-material addition level and keep the same basis across purchasing, R&D and marketing.
Formulation strategy
Choose a pH window compatible with the peptide, preservative and supporting actives. Follow grade-specific temperature and order-of-addition guidance. In a multi-peptide formula, calculate the combined carrier and salt load because these can affect viscosity, clarity and preservation.
Stability and packaging
Monitor pH, appearance, haze, odor, viscosity and relevant chemical markers in the final package. A transparent serum that looks unchanged may still require assay data when a quantified peptide claim is central. Validate pump or dropper dose, leakage and weight loss.
Evidence boundaries
Penetration studies using microemulsions or peptide hydrogels answer delivery questions about those exact systems. They do not prove performance of every water-based serum. Cosmetic claims should reflect the commercial grade and finished-product substantiation.
Buyer checklist
Confirm identity, sequence or analytical support, active basis, carrier, preservative, pH, storage, COA, SDS, MOQ, lead time, sample representativeness and change notification before approving the material.
Selected research for further reading
These sources provide background and do not substitute for finished-product substantiation.
Need a product-specific specification?
Send the peptide, format, quantity, packaging and destination market. We will confirm composition, MOQ, documents and sample options.
Ask the B2B TeamPublished August 12, 2026. Educational B2B content; not medical advice.