Acetyl Tetrapeptide-3

What it is

Acetyl Tetrapeptide-3 is a synthetically produced peptide made up of four amino acid building blocks with an acetyl group at one end. Peptides of this kind are purposely designed and are usually used in cosmetic raw materials at very low proportions, frequently within finished active complexes alongside plant extracts. Its origin is synthetic. That is factual information, not an assessment.

The promoted function lies in the area of hair density and anchoring of the hair. A distinction matters here that product communication regularly blurs: the safety question — does the skin tolerate the substance? — and the efficacy question — does it deliver what it promises? — are two separate questions with separate evidence. The classification above relates solely to the safety question. More on efficacy below.

Why

• On safety: peptides made of a few amino acid building blocks are body-like molecules and are used at very low levels. Molecular size and use level together imply limited uptake through the skin. I am not aware of indications of relevant irritation or sensitisation potential for this substance — but that is an absence of indications, not proof of harmlessness. Hence the low confidence.
• On efficacy — this is the actual point: the available evidence for hair-growth-related effects comes predominantly from investigations by raw material manufacturers, often with small participant numbers and mostly with active complexes rather than the single substance. Independent, sufficiently large studies are not known to me. Efficacy is therefore not disproved, but neither is it established in a form that would support an efficacy claim towards customers.
• Why this distinction matters in practice: a substance can simultaneously be well tolerated and insufficiently supported in its effect. Taken together that is not a safety problem but a communication problem. Using tolerance as evidence of efficacy swaps two different questions.
• What the substance reliably contributes in the product additionally depends on concentration, formulation and mode of use. That information is not available here.

When the assessment differs

• Hair loss with a medical cause: a cosmetic product is not a treatment. With persistent or sudden hair loss the cause belongs in medical or dermatological hands. This page does not replace that and makes no statement about an individual case.
• Expectations: the classification “low risk” concerns tolerance. It is expressly not a confirmation that a visible effect will occur.
• Sensitive or pre-damaged scalp: what matters generally is the tolerance of the whole product, not of a single constituent. Peptides are not the typical trigger here; other constituents can be.
• Active complexes: where the substance is used as part of a complex with plant extracts, tolerance questions more often concern the extract than the peptide. That is not assessed here.

Open questions

• Efficacy evidence: the available investigations come predominantly from raw material manufacturers and have not been examined here in their wording. Participant numbers, study design, comparison group and endpoints are open. As long as that is the case, no efficacy claim may be derived from this page.
• Separating single substance from active complex: whether reported effects are attributable to the peptide, to the accompanying plant extract or to the combination has not been clarified here.
• Safety data: no verified data on sensitisation and irritation potential for this substance. That is the reason for the low confidence despite the low risk classification.
• Regulatory status: not examined; the entry in the EU CosIng database must be checked, with its date.
• Concentration in a specific product: not available.
• Environmental data: not examined.

Related substances

Applies to: Amino acids and peptides

• Alanine — Amino acid, moisture-binding
• Arginine — Amino acid (conditioning, pH adjustment)

Further substances from the same group for which a long-form assessment already exists.