Polyepsilon-Lysine

What is Polyepsilon-Lysine?

Polyepsilon-Lysine is a cationic homopolymer composed of multiple L-lysine units linked through their epsilon-amino groups, produced via fermentation by the bacterium Streptomyces albulus. This naturally derived ingredient belongs to the class of antimicrobial peptides and conditioning polymers commonly found in hair care and skin care formulations like shampoos, conditioners, cleansers, and lotions. In products, it functions by adsorbing onto negatively charged surfaces such as hair keratin or skin proteins, reducing friction and static electricity for improved manageability. Its amphiphilic structure lowers surface tension to aid in cleansing and foaming, while stabilizing oil-water mixtures as an emulsifier. Additionally, it disrupts microbial cell membranes, contributing to product preservation without harsh synthetic preservatives.

Comedogenic Rating 0/5 Low risk of clogging pores

EWG Safety Rating 1 View on EWG →

Roles in Formulation

This ingredient serves the following purposes in cosmetic formulations:

Hair conditioning

Improves softness, shine, and manageability by reducing friction and static; commonly achieved with cationic agents, silicones, oils, or conditioning polymers.

Skin conditioning agent

Maintains skin softness, smoothness, and flexibility.

Surfactant

Lowers surface tension to enable cleansing, emulsifying, and foaming; central to shampoos, body washes, and many emulsions and micellar systems.

Emulsifying agent

Enables stable mixing of oil and water phases by forming an interfacial film, helping create lotions, creams, and cleansers with consistent texture.

Benefits

Supports hair softness, shine, and ease of combing by minimizing static and friction.

Promotes skin smoothness and flexibility through gentle conditioning action.

Assists in creating stable emulsions and effective cleansing in formulations.

Who It's For

A quick guide for who this ingredient may suit (and who should be cautious).

Who May Benefit	Who Should Avoid
Individuals with dry or frizzy hair seeking natural conditioning.	Those with known allergies to lysine-based compounds.
People with normal to sensitive skin wanting mild surfactants.	People sensitive to cationic polymers in rinse-off products.
Users preferring fermented, antimicrobial ingredients in clean beauty products.	Individuals experiencing irritation from fermented ingredients.

Safety Notes

Considered low hazard with minimal risk of irritation or sensitization.
Non-comedogenic, unlikely to clog pores in skincare applications.

Frequently Asked Questions about Polyepsilon-Lysine

What is Polyepsilon-Lysine derived from?

It comes from fermenting the bacterium Streptomyces albulus, yielding a polymer of lysine amino acids.

Is it safe for sensitive skin?

It has a low irritation profile, suitable for many sensitive skin types based on safety assessments.

What roles does it play in cosmetics?

Acts as a conditioner, surfactant, and emulsifier to improve texture and stability.