Pentapeptides: Your Clean Clinical Anti-Aging Guide

Pentapeptides are amino acid sequences made of exactly five amino acids. In skincare, the best-known ones are Palmitoyl Pentapeptide-4 (the original Matrixyl, studied for the look of fine lines), Pentapeptide-18 (Leuphasyl, used for expression lines) and Myristoyl Pentapeptide-17 (used in lash and brow formulas). They do different jobs, so the right one depends on the result you want to see.

The word "pentapeptide" describes length, not function. Two pentapeptides can behave as differently as two five-letter words. In this guide I sort the cosmetic pentapeptides by what they do, show which ones have published human data and which rely only on supplier claims, and give you practical rules for using them at home. If you are specifically choosing between Palmitoyl Tripeptide-5 and Palmitoyl Pentapeptide-4, my head-to-head comparison of Palmitoyl Tripeptide-5 vs Pentapeptide-4 goes deeper on that pair.

How peptide names work

Cosmetic peptide names on an INCI list follow a simple pattern:

• The prefix tells you the length: di (2), tri (3), tetra (4), penta (5), hexa (6), octa (8).
• The number after the dash is a registry number, not a strength. Pentapeptide-18 is not "stronger" than Pentapeptide-4. They are simply different sequences registered at different times.
• A fatty acid in front (palmitoyl, myristoyl) or an acetyl group means the sequence has been attached to another molecule, usually to change how it behaves on the skin surface or how stable it is.

So "Palmitoyl Pentapeptide-4" reads as: a five-amino-acid sequence, registry number 4, attached to palmitic acid.

The cosmetic pentapeptides, sorted by job

That last column matters more than any marketing claim. Only two cosmetic pentapeptides on this list have human studies I could verify. The rest are supported by supplier documents, which are useful for mechanism and use levels but are not independent trials.

Palmitoyl Pentapeptide-4: the collagen-fragment sequence

The story starts with a lab finding. Katayama and colleagues (1993, Journal of Biological Chemistry) identified the five-amino-acid sequence Lys-Thr-Thr-Lys-Ser (KTTKS), a fragment of type I procollagen, as the minimum sequence needed to increase collagen and fibronectin production by fibroblasts in cell culture. That was a laboratory study, not a skincare trial.

Attaching palmitic acid produced pal-KTTKS, which became Palmitoyl Pentapeptide-4. Robinson and colleagues (2005, International Journal of Cosmetic Science) then tested it in people: 93 Caucasian women aged 35 to 55 used a moisturizer with 3 ppm pal-KTTKS on one side of the face and the same moisturizer without it on the other, for 12 weeks. Fine line and wrinkle measurements improved on the peptide side, and the product was well tolerated. One caution in reading that trial: several results reached significance only at a less strict statistical threshold, so I describe it as encouraging rather than conclusive.

Common confusion: Matrixyl 3000 is not a pentapeptide. Its INCI shows two sequences, Palmitoyl Tripeptide-1 and Palmitoyl Tetrapeptide-7. Both Matrixyl products come from the same supplier family, which is why the names get mixed up on blogs. You can read the full breakdown on our Matrixyl 3000 Serum Booster product page.

Pentapeptide-18: the expression-line pentapeptide

Pentapeptide-18 is sold as Leuphasyl. The Spec-Chem catalogue describes its mechanism as coupling to the enkephalin receptor on nerve cells, which reduces acetylcholine release and so lowers the intensity of muscle contraction behind expression lines (supplier mechanism). That is why you see it called a "Botox in a bottle" type ingredient. It is not Botox, it is a topical cosmetic ingredient, and topicals are a gentler, needle-free approach.

The human data: Dragomirescu and colleagues (2014, Cosmetics) had 20 volunteers apply emulsions with 0.5%, 1% or 2% Leuphasyl daily over the mimic muscles for 2 months. Only the 2% emulsion produced a meaningful result: average wrinkle size was measured 34.7% smaller in the frown-line area and 28.4% smaller around the eyes. Limitations: a small group, no placebo group described, and 2D imaging that cannot measure depth.

Pentapeptide-18 is usually paired with Acetyl Hexapeptide-8 (Argireline), because the two act at different points of the same nerve-to-muscle signal. At Skin Perfection you will find that pairing in two places:

• Argirelox Peptide Dual Expression Line Serum Booster: INCI Aqua, Glycerin, Acetyl Hexapeptide-8, Pentapeptide-18, Citric Acid, Caprylyl Glycol. Use it at the level stated on its label.
• Super Peptide Anti-Aging Serum: a finished serum listing 10% Leuphasyl alongside 10% Argireline, 10% Snap-8, 20% Matrixyl 3000, 15% Syn-Coll and three other complexes.

Myristoyl Pentapeptide-17: lashes and brows

Myristoyl Pentapeptide-17 (sequence Lys-Leu-Ala-Lys-Lys attached to myristic acid) appears in lash and brow complexes. Our Eyelash Peptide for Lashes and Brows lists it with Biotinoyl Tripeptide-1, Myristoyl Hexapeptide-16, Myristoyl Tetrapeptide-12 and panthenol. In cosmetic terms, these complexes are used for the look of fuller, more conditioned lashes and brows. I could not find an independent human trial for this sequence, so I rely on supplier documents for its use level and do not quote performance numbers.

How to use pentapeptides at home

Formulating rules from the bench

• Add them cool. Peptide boosters go in after any heated phase has cooled below 40°C (104°F), or straight into a finished serum or cream.
• Keep them out of strong acids. Do not mix peptide boosters into acid peels or low-pH exfoliants; use those on separate nights.
• Use the manufacturer's highest rate. For Pentapeptide-18, the only human data I found showed results at 2% Leuphasyl, not at 0.5% or 1%. Lower is not a safe shortcut, it is often just ineffective.
• Preserve water-based blends. If a booster has no preservative of its own, add a broad-spectrum preservative such as Leucidal SF Complete at 4%, which is 36 drops per ounce.
• Refrigerate opened boosters and use a mixed serum within the time frame your preservative supports.

An expression-line serum built around Argirelox

Because I only publish rates I can confirm on the label or supplier sheet, this blend uses Argirelox at its label rate and adds two boosters at their highest manufacturer rates (9 drops = 1% per fluid ounce):

Shake 30 seconds, refrigerate, and apply 2 to 3 drops to the forehead, between the brows and at the outer eye corners morning and night, followed by moisturizer.

Sensitive skin

Patch test any new peptide blend on the inner arm for 24 hours. If your skin is sensitive, start each booster at the lowest rate of its recommended range (for example Snap-8 at 3%, 27 drops per ounce, and Syn-Ake at 1%, 9 drops per ounce) and work up over several weeks.

What to expect, and when

• Expression-line pentapeptides (Pentapeptide-18): the human study above measured results over 2 months of daily use.
• Signal pentapeptides (Palmitoyl Pentapeptide-4): the split-face trial ran 12 weeks, with some measures changing from week 4 or 8.
• Either type: results depend on consistent daily use. Stop using it and the look of lines gradually returns, the same as with any topical.

Want a broader view of peptide families before you choose? See my guide to Argireline serums for how the hexapeptide side of the pairing works.

Frequently asked questions

Are pentapeptides better than tripeptides or hexapeptides?

No. Length alone does not predict results. Each sequence is studied on its own, so compare the evidence for the specific INCI name, not the prefix.

Is Matrixyl 3000 a pentapeptide?

No. Matrixyl 3000 contains Palmitoyl Tripeptide-1 and Palmitoyl Tetrapeptide-7. The original Matrixyl is Palmitoyl Pentapeptide-4.

Can I use pentapeptides with retinol or vitamin C?

With retinol, yes: apply the peptide serum first and retinol after, or use them on alternate nights. With low-pH vitamin C (L-ascorbic acid), apply them at different times of day so the peptide is not sitting in a very acidic layer.

Is Pentapeptide-18 the same as Botox?

No. It is a topical cosmetic ingredient that works on the skin surface with no needles. It is often compared with Botox because it targets the look of expression lines, and as a topical it is a gentler option.

How much Palmitoyl Pentapeptide-4 is in a product?

Very little by weight. The Robinson trial used 3 ppm (0.0003%) of the peptide itself. Supplier solutions are diluted, which is why booster rates look much higher than the peptide content.

Sources

1. Katayama K, Seyer JM, et al. A pentapeptide from type I procollagen promotes extracellular matrix production. Journal of Biological Chemistry. 1993. doi:10.1016/S0021-9258(18)82153-6 (cell culture)
2. Robinson LR, Fitzgerald NC, Doughty DG, Dawes NC, Berge CA, Bissett DL. Topical palmitoyl pentapeptide provides improvement in photoaged human facial skin. International Journal of Cosmetic Science. 2005;27(3):155-160. doi:10.1111/j.1467-2494.2005.00261.x (n=93, 12 weeks)
3. Dragomirescu AO, Andoni M, Ionescu D, Andrei F. The efficiency and safety of Leuphasyl, a Botox-like peptide. Cosmetics. 2014;1(2):75-81. doi:10.3390/cosmetics1020075 (n=20, 2 months)
4. Schagen SK. Topical peptide treatments with effective anti-aging results. Cosmetics. 2017;4(2):16. doi:10.3390/cosmetics4020016 (review)
5. Spec-Chem Industry, Ingredients Catalogue 2026 V1 (supplier data: Pentapeptide-18, Pentapeptide-3, Acetyl Pentapeptide-1, Palmitoyl Pentapeptide-4 mechanisms).
6. Spec-Chem, PEPTIDES+ catalogue V3.0 (supplier data: SpecPlex GPS with Palmitoyl Pentapeptide-4; Lash1617 with Myristoyl Pentapeptide-17; SoothFine with sh-Pentapeptide-1).
7. Skin Perfection product labels: Argirelox, Super Peptide Anti-Aging Serum, Eyelash Peptide, Snap-8 and Syn-Ake usage rates.

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

About the Author
Written by Kari Thomas, cosmetic formulator and founder of Skin Perfection.