Rh-Polypeptide-125: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: June 30, 2025
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We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Rh-Polypeptide-125?

Rh-Polypeptide-125 is a lab made version of a human protein related to platelet-derived growth factor C. Scientists take the gene that tells our cells how to make this protein, tweak it so that bacteria can read it, then place it inside friendly strains of E. coli. As the bacteria grow in fermentation tanks they produce the peptide, which is later purified so only the desired chain of up to 345 amino acids remains. The chain may include natural links called disulfide bonds and can carry small sugar groups, mirroring how the protein appears in the body.

The idea of using growth factor-inspired molecules in beauty care took off in the early 2000s when researchers noticed their potential to support skin and scalp wellness without medical claims. Once production methods became more efficient and cost-friendly Rh-Polypeptide-125 began appearing in high-end hair products that focused on strength and fullness.

Today you will most often find Rh-Polypeptide-125 in rinse-off and leave-on hair masks, scalp serums, thickening sprays and premium shampoos or conditioners aimed at boosting volume and improving overall strand health.

Rh-Polypeptide-125’s Cosmetic Benefits/Uses

This peptide serves one main purpose in cosmetic formulas.

Hair conditioning: Rh-Polypeptide-125 helps coat and smooth the hair shaft, making strands feel softer and easier to manage. Regular use can lead to improved shine, less breakage from brushing and a fuller appearance because conditioned hair reflects light more evenly and resists frizz.

Who Can Use Rh-Polypeptide-125

Because this peptide is lightweight and non-comedogenic it suits virtually all scalp and hair types including dry, oily and sensitive. There are no known reasons it would aggravate common skin conditions such as dandruff or seborrheic dermatitis, though individual sensitivities can always exist.

Rh-Polypeptide-125 is created through bacterial fermentation without any animal-derived materials so it is considered suitable for vegans and vegetarians.

Current cosmetic safety reviews have not flagged special restrictions for pregnant or breastfeeding women when this ingredient is applied topically. Still, this is not medical advice and anyone who is expecting or nursing should show the full product ingredient list to a qualified healthcare professional before use.

The peptide does not make skin or hair more prone to sunburn so it is not linked to photosensitivity. It also layers well with common hair care actives such as niacinamide, panthenol and plant oils.

Potential Side Effects/Adverse Reactions

Responses to any cosmetic ingredient can differ from person to person. The effects below are possibilities rather than probabilities and most people will not notice any issues when formulas are produced and used as directed.

  • Mild scalp irritation – tingling, itching or a warm sensation can occur in very sensitive users
  • Allergic contact dermatitis – rare swelling, redness or rash due to an immune response to the peptide or other formula components
  • Eye irritation – stinging or watering if the product accidentally drips into the eyes
  • Product buildup – overuse in leave-on treatments might weigh hair down or make strands feel coated

If any uncomfortable reaction develops stop using the product and consult a healthcare professional if symptoms persist or worsen.

Comedogenic Rating

Comedogenic rating: 0/5. Rh-Polypeptide-125 is a large water-soluble protein that stays on the hair surface rather than penetrating facial pores. It contains no oily or waxy material that could clog follicles so it is considered non-comedogenic.

It is therefore suitable for people prone to acne or breakouts.

The peptide is typically used at low levels and often in rinse-off formats which further minimizes any chance of pore congestion.

Summary

Rh-Polypeptide-125 is a biotech peptide that conditions hair by forming a lightweight smoothing film which reduces friction, boosts shine and helps strands appear fuller.

Though not as mainstream as oils or keratin it enjoys growing popularity in high-end hair masks serums and volumising sprays thanks to its science-backed appeal.

Overall safety is high with low irritation potential and zero comedogenicity but every scalp is unique so perform a quick patch test when trying any new product containing this ingredient.

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