Acetyl Tetrapeptide-3 (Capixyl)
Acetyl Tetrapeptide-3 with Biochanin A (marketed as Capixyl)
Two-component complex with plausible mechanisms but thin clinical evidence and key claims traceable to fabricated citations.
How Acetyl Tetrapeptide-3 (Capixyl) works — and how well we know it
Capixyl is a two-component system: acetyl tetrapeptide-3 (Ac-Lys-Gly-His-Lys) stimulates extracellular matrix proteins (collagen III, laminin) around the hair follicle, while the red clover extract (standardized to biochanin A) inhibits 5-alpha reductase in vitro, reducing DHT production. The peptide and the isoflavone target different pathways, but virtually all clinical data tests the combination, not either component alone.
topical
Capixyl is typically used at 1-5% concentration in topical serums and lotions. The manufacturer's clinical study used 5% Capixyl lotion applied twice daily.
Cosmetic ingredient. No FDA or EMA approval for hair loss. Sold as part of the proprietary Capixyl complex by Lucas Meyer Cosmetics (now Clariant/IFF).
Cosmetic adjunct to proven treatments for those seeking a peptide-based addition to their regimen.
Evidence distribution across 6 claims
Why the grade is D. One small manufacturer-sponsored RCT (N=30), two most-cited statistics trace to unverifiable or fabricated citations, no study has tested the peptide alone in humans, and the anti-DHT activity belongs to the red clover extract, not the peptide.
What the studies actually showed
30 men with AGA (15 Capixyl, 15 placebo)
32 subjects (16 male, 16 female) with mild-to-moderate AGA (Norwood III-IV / Ludwig I-II)
106 men with AGA
Male subjects, average age 45
23 volunteers
45-90 days based on manufacturer data. The Loing et al. RCT measured at 4 months. The Lueangarun study measured at 24 weeks. No rigorous dose-response or time-course data from independent studies.
Unknown. The longest controlled study is 24 weeks (Lueangarun). No data on whether effects continue to improve beyond 6 months.
Yes — must continue indefinitely
No published discontinuation data. As a cosmeceutical acting on ECM maintenance and (via biochanin A) local DHT levels, effects are presumed to reverse upon stopping use, similar to other topical hair treatments. However, this has not been formally studied.
Side effects, contraindications, and special populations
| Adverse event | Rate | Placebo | Notes |
|---|---|---|---|
| Local scalp irritation | Very rare (not reported in clinical studies) | — | No local adverse reactions were reported in the Lueangarun 2020 RCT (N=32) or the Loing 2013 manufacturer study (N=30). Individual sensitivity is possible but appears uncommon. |
| Eye irritation | Not quantified | — | The peptide can irritate eyes on direct contact. Standard precaution: wash hands after application to scalp. |
- Known allergy to any component (acetyl tetrapeptide-3, Trifolium pratense / red clover extract, biochanin A)
- Known sensitivity to isoflavones or phytoestrogens (theoretical, based on biochanin A content)
- Hormonal therapies (oral contraceptives, estrogen, progesterone) (Theoretical / low concern for topical use) — Biochanin A is a phytoestrogen. Systemic interactions are documented for oral red clover supplements, but topical application at cosmetic concentrations delivers negligible systemic exposure. The concern is largely theoretical for topical Capixyl.
- Topical minoxidil or other topical hair treatments (None expected) — No known interaction. Capixyl is commonly layered with minoxidil in consumer regimens without reported issues.
No formal reproductive toxicity studies have been conducted on Capixyl. Biochanin A is a phytoestrogen and red clover is contraindicated orally during pregnancy. While topical application delivers minimal systemic exposure, the precautionary principle suggests avoiding use during pregnancy and lactation until safety data are available.
Studied in women in the Lueangarun 2020 trial (16 female subjects, Ludwig I-II AGA). No sex-specific adverse events reported. Considered safe for topical use in women.
No clinical data in children. European regulations do not restrict acetyl tetrapeptide-3 concentration in cosmetics. Some sources note topical application is not discouraged for children over 3 years old, but no pediatric hair loss studies exist.
Every claim, traced back to its source
We took every major claim made about Acetyl Tetrapeptide-3 (Capixyl) and matched it to the specific experimental model behind it. Click a claim to see the model, the finding, and our assessment of how much weight it deserves.
6 claims · evidence-by-evidence breakdown
1RCTWeight: Very LowCapixyl produces a 17% increase in hair diameterSource citation appears fabricated; the claimed 17% figure cannot be independently verified.
Unverifiable. This figure is frequently attributed to "Garcia A., Stuard B., & Wendt J. (2015). Clinical efficacy of a hair serum containing acetyl tetrapeptide-3. International Journal of Trichology, 7(4), 148-152." However, this paper does not exist on PubMed. The International Journal of Trichology Volume 7, Issue 4 (2015) does not contain this article. The citation appears to have been fabricated or hallucinated by marketing content writers and propagated across cosmetics websites.
The 17% figure likely originates from the Lucas Meyer Cosmetics proprietary technical data file, which is not publicly accessible as a peer-reviewed publication. The only peer-reviewed study from the manufacturer (Loing et al., 2013) reports anagen/telogen ratio changes, not hair diameter.
You cannot give weight to a claim whose source study doesn't exist. This is a significant red flag for anyone evaluating Capixyl: one of its most-cited statistics traces back to a fabricated citation. The actual manufacturer data may show something about diameter changes, but it hasn't been published in a journal where it can be evaluated by independent scientists.
- Garcia A, Stuard B, Wendt J (2015). Clinical efficacy of a hair serum containing acetyl tetrapeptide-3. International Journal of Trichology (CLAIMED -- paper does not exist in this journal)
2RCTWeight: Very LowCapixyl produces a 67% boost in hair growth activityThe 67% figure is either unverifiable or a misquotation of a responder rate, not a growth improvement metric.
Same situation as Claim 1 -- attributed to the same non-existent "Garcia et al., 2015" citation.
The only peer-reviewed study from the manufacturer (Loing et al., 2013, N=30) found a 46% increase in anagen/telogen ratio with the Capixyl combination -- not 67%. The 67% figure may come from a different metric in the proprietary technical file (the manufacturer's pilot trial reported that "67% of the 18 Capixyl volunteers showed significant improvement"), but this is a percentage of responders, not a percentage improvement in growth. It appears someone converted "67% of people improved" into "67% boost in hair growth activity" -- a fundamental misrepresentation.
The published evidence shows a 46% improvement in A/T ratio (Loing et al., 2013), which is a reasonable metric. But the "67%" claim is either unverifiable or a misquotation of a different statistic entirely. This is common in cosmetic ingredient marketing: a real number gets separated from its context and turned into a different, more impressive-sounding claim.
- Loing E et al. (2013). A new strategy to fight androgenetic alopecia beyond the androgen pathway. J Cosmet Sci PMID 23449130
- Garcia A, Stuard B, Wendt J (2015). Clinical efficacy of a hair serum containing acetyl tetrapeptide-3 (CLAIMED -- paper does not exist). International Journal of Trichology (CLAIMED)
3In VitroWeight: Low to ModerateAcetyl tetrapeptide-3 strengthens the extracellular matrix around folliclesReal ECM stimulation data, but tested in lung cells (not scalp) by the manufacturer with no direct hair anchoring measurement.
In vitro -- MRC5 human fibroblasts (a lung-derived cell line, not scalp fibroblasts or dermal papilla cells). Cells were treated with 10^-7 M acetyl tetrapeptide-3 and measured via immunofluorescence. Also ex vivo -- human skin explants for collagen VII at the dermal-epidermal junction. This data was tested on the peptide alone (not the combination).
Type III collagen expression: +65% vs untreated control. Laminin expression: +285% vs control. Collagen VII at the dermal-epidermal junction was restored to baseline after corticoid-induced reduction. These are real findings from the manufacturer's published paper.
The ECM data is the strongest evidence for the peptide component specifically. The increases in collagen III and laminin are significant in magnitude. However: (1) MRC5 fibroblasts are lung cells, not scalp cells -- the same compound might behave differently in dermal papilla fibroblasts. (2) This is in vitro data -- cells in a dish don't replicate the conditions of your scalp. (3) The study was conducted by the manufacturer's own R&D department (Lucas Meyer Cosmetics), not by independent researchers. (4) No direct measurement of hair anchoring force was performed -- the claim that ECM strengthening means better anchoring is logical but untested.
- Loing E et al. (2013). A new strategy to fight androgenetic alopecia beyond the androgen pathway. J Cosmet Sci PMID 23449130
4In VitroWeight: ModerateCapixyl reduces DHT / inhibits 5-alpha reductaseAnti-DHT activity is real but belongs to biochanin A (red clover), not the peptide. Products attributing DHT reduction to the peptide are misleading.
In vitro -- human genital skin fibroblasts and benign prostatic hyperplasia tissue homogenates. This is independent academic research from the University of Wales (Evans et al., 1995). CRITICAL: This evidence is for biochanin A (the red clover extract), NOT for acetyl tetrapeptide-3 (the peptide).
At 100 micromolar concentration, biochanin A caused >80% inhibition of 5-alpha reductase activity. In rat prostate tissue, the IC50 was 140 micromolar. The manufacturer claims a "93% reduction in DHT" in their marketing materials, but the source study for this specific number is not publicly available -- it likely comes from a proprietary in vitro assay.
The anti-DHT activity is real and independently confirmed -- but it belongs to the red clover extract, not the peptide. If a product page tells you "acetyl tetrapeptide-3 reduces DHT," that's misleading. The peptide has no demonstrated 5-alpha reductase inhibitory activity. It's an ECM stimulator, not an anti-androgen. Any product containing Capixyl gets its anti-DHT effect from biochanin A, which is a plant isoflavone available in many cheaper formulations.
- Evans BAJ et al. (1995). Inhibition of 5-alpha reductase in genital skin fibroblasts and prostate tissue by dietary lignans and isoflavonoids. J Endocrinol PMID 7490559
5RCTWeight: Low to ModerateClinical trials show Capixyl improves hair growth comparable to minoxidilReal but thin clinical evidence: one small manufacturer RCT, and independent studies only tested multi-ingredient formulas.
Multiple human trials, but with important caveats: Study A (manufacturer, 2013): N=30, RCT, 5% Capixyl lotion vs placebo, 4 months. Anagen density +13%, telogen density -29%, A/T ratio +46%. Manufacturer-sponsored (Loing et al.). Study B (independent, 2020): N=32, triple-blind RCT, herbal combo containing Capixyl components + ginseng vs 3% minoxidil, 24 weeks. Hair count: herbal +8.3% vs minoxidil +8.68% (not significant). Hair Mass Index: herbal +13.8% vs minoxidil +31.48% (not significant). (Lueangarun & Panchaprateep.) Study C (2019): N=106, RCT, Redensyl+Capixyl+Procapil (RCP) vs 5% minoxidil, 24 weeks. RCP group scored higher by researcher and photographic assessment. Published in a questionable journal. Tests triple combination.
The manufacturer study shows a real difference vs placebo. The independent study shows rough comparability to 3% minoxidil (not the standard 5%). The RCP study shows a triple-ingredient combination outperforming minoxidil, but you can't attribute that to Capixyl specifically.
The clinical evidence is real but thin. Key problems: (1) The manufacturer study (N=30) is small, short (4 months), and funded by the company that sells Capixyl. (2) The independent study compared against only 3% minoxidil (not the standard 5%) and included ginseng extract in the formula. (3) The RCP study tested three ingredients together. (4) No study has tested acetyl tetrapeptide-3 alone in humans. (5) The placebo group in the manufacturer study inexplicably worsened significantly (-33% A/T ratio), which inflates the apparent treatment effect. Bottom line: there's enough signal to say Capixyl probably does something, but the evidence is nowhere near the standard of proof for minoxidil or finasteride.
- Loing E et al. (2013). A new strategy to fight androgenetic alopecia beyond the androgen pathway. J Cosmet Sci PMID 23449130
- Lueangarun S, Panchaprateep R (2020). An herbal extract combination (Capixyl) is comparable to 3% minoxidil solution for hair growth in men with androgenetic alopecia. J Cosmet Dermatol PMID 33584955
- Karaca N, Akpolat ND (2019). Comparison of Redensyl, Capixyl, Procapil combination vs minoxidil 5%. Hilaris Publisher
6In VitroWeight: Very LowAcetyl tetrapeptide-3 has skin anti-aging benefitsTheoretical only -- no clinical skin anti-aging data. The peptide should not inherit evidence from the related GHK-Cu peptide.
In vitro only -- MRC5 fibroblasts showing collagen III and laminin stimulation (same data as Claim 3). No dedicated skin anti-aging clinical trials on acetyl tetrapeptide-3 were identified.
The collagen III and laminin increases seen in vitro theoretically translate to firmer, more structured skin. But this has not been tested clinically for facial anti-aging.
The peptide is marketed almost exclusively for hair. Its ECM-stimulating mechanism could theoretically benefit skin, but without clinical data, this remains speculative. The parent peptide sequence (KGHK) is structurally related to GHK (which has extensive skin evidence when complexed with copper), but acetyl tetrapeptide-3 is not GHK-Cu and shouldn't inherit its evidence base.
- Loing E et al. (2013). A new strategy to fight androgenetic alopecia beyond the androgen pathway. J Cosmet Sci PMID 23449130
What's still missing from the science
- Any clinical trial testing acetyl tetrapeptide-3 alone (without red clover) in humans for hair.
- Independent replication of the manufacturer's in vitro ECM data.
- A properly powered, independent RCT comparing Capixyl to standard-dose (5%) minoxidil with a placebo arm.
- Any data on whether biochanin A's in vitro 5-alpha reductase inhibition translates to meaningful DHT reduction when applied topically to human scalp at the concentrations present in Capixyl serums.
- Verifiable sources for the two most-cited claims (17% diameter increase, 67% growth boost).
- Hair diameter or density data measured by any method other than TrichoScan in the manufacturer's study.
Our verdict on Acetyl Tetrapeptide-3 (Capixyl)
Not in our formulary yet
We don't carry this ingredient. We only formulate around actives where the evidence — and the safety profile — is strong enough to recommend with confidence. As the data matures, we may revisit.
From the Anagen blog
Long-form analysis and primary-source breakdowns that go beyond the summary above.
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