Cosmetic and topical
Skin & aging
Pentapeptide-18
Also called Leuphasyl
Pentapeptide-18 (Leuphasyl) is a cosmetic peptide used for the look of expression lines. Learn how it works, where it is used, and how strong the evidence is.
- Reviewed by
- William Maish, MD MBA MPH, Clinical Product Lead
- Published
- October 5, 2026
- Last updated
- October 5, 2026
Key takeaway
Pentapeptide-18 is a synthetic five-amino acid peptide, sold as Leuphasyl, used in skincare to target expression lines. Laboratory work suggests it mimics a natural "calming" messenger that reduces the release of the neurotransmitter that triggers muscle contraction, which is the basis for its use in products aimed at the look of dynamic wrinkles. As of 2026, the support is laboratory and manufacturer data, with human testing done only inside combination formulas rather than on the peptide alone.
At a glance
| What it is | Cosmetic ingredient, a neuro-inspired "expression line" peptide (sold as Leuphasyl) |
| FDA status | Does not require FDA approval, as a cosmetic ingredient rather than a drug |
| Research | Activity rests on laboratory and manufacturer data; human evidence comes from combination formulas |
| Used in | "Anti-aging" products for the look of expression lines, often alongside Argireline |
| Evidence strength | Low research |
What is pentapeptide-18?
Pentapeptide-18 is a synthetic peptide of five amino acids, modeled on enkephalin, one of the body's natural signaling peptides. It is made by Lipotec under the trade name Leuphasyl and is used in skincare aimed at the appearance of expression lines. It is a cosmetic ingredient, not a drug, and is often paired with other "expression line" peptides.
How does it work?
Laboratory studies describe pentapeptide-18 as a peptide that quiets the signal driving muscle contraction, but at an earlier step than some related peptides. The proposed mechanism runs in steps:
- As an enkephalin mimic1, it binds receptors2 on the nerve ending.
- Those receptors in turn reduce the inflow of calcium.
- Because calcium is needed to release acetylcholine, the neurotransmitter that tells muscle to contract, less acetylcholine is released.
- The small muscles that form expression lines contract less.
It is marketed as working in tandem with Argireline3, which acts at a different point in the same release pathway.
These are laboratory and manufacturer findings, and a topical cosmetic does not reach or paralyze muscle the way an injection does. In finished products the benefit is described in appearance terms, the look of softer, smoother expression lines.
Is it FDA-approved?
No, and it does not need to be. The FDA does not pre-approve cosmetic ingredients. A cosmetic may describe effects on the appearance of skin, while a claim to relax muscles or change the body's function would make a product a drug. Pentapeptide-18 is used as a cosmetic ingredient, for the appearance of the skin.
What is it used for?
Pentapeptide-18 is used in "anti-aging" serums and creams aimed at dynamic or expression lines, such as forehead lines and crow's-feet. The appearance goal is smoother-looking skin and a reduction in the look of movement-related lines. It is frequently combined with acetyl hexapeptide-8 (Argireline) and other actives.
What does the research show?
The direct evidence for the isolated peptide is limited. According to PubMed, the peptide-specific research is largely computational and laboratory work, such as a modeling study2 of how it interacts with its target. Where it has been tested on people, it has been combined with other actives, for example within retinol-loaded formulations4, so the effect cannot be attributed to pentapeptide-18 alone. No independent human trial of the ingredient by itself was found.
What are the side effects?
Pentapeptide-18 is generally reported as well tolerated on the skin, with low irritation potential at cosmetic use levels, and topical use is not known to produce a systemic nerve or muscle effect. Independent safety data are limited, so a patch test is reasonable for sensitive skin.
More for skin & aging
Sources: a molecular modeling study of pentapeptide-18 (Akhan et al., Computational Biology and Chemistry, 2026, DOI: 10.1016/j.compbiolchem.2026.1089522); and a study of retinol-and-peptide formulations tested on volunteers (Pawłowska et al., Life, 2024, DOI: 10.3390/life141012124), both indexed on PubMed. This document is educational and does not constitute medical advice.