What Is Pei-1500?
Pei-1500 is the cosmetic label name for a synthetic material known chemically as aziridine homopolymer. In simple terms it is a chain of small three-membered rings called aziridines that have been linked together to form a flexible water-soluble polymer. It is produced in a controlled laboratory setting where individual aziridine units are polymerized under carefully monitored temperature and pH conditions, then purified to remove unreacted monomers and by-products. Because the process is man-made, there is no plant or animal source involved and the final ingredient is consistent from batch to batch.
The first commercial uses of aziridine polymers appeared in the late 1960s in the paper and textile industries, where their film-forming properties helped improve surface strength. Formulators soon noticed that the same thickening ability could stabilize creams and lotions, so cosmetic chemists adapted the polymer for personal care. Today Pei-1500 is valued for the way it controls viscosity without adding a heavy feel.
You will most often find Pei-1500 in rinse-off and leave-on products that need a smooth pour or pump action such as facial cleansers, lightweight lotions, sheet mask essences, hydrogel masks, anti-aging serums and some hair conditioning sprays. It is usually added at low levels during the cooling phase of production where it quickly hydrates and brings the formula to its target thickness.
Pei-1500’s Cosmetic Benefits/Uses
Pei-1500 offers a single but very useful function in personal care formulas
Viscosity controlling: By swelling in water and interacting with other ingredients, Pei-1500 fine-tunes the flow and thickness of a product. This helps prevent phase separation, keeps suspended actives evenly distributed and ensures the product spreads easily across skin or hair. The result is a more stable formula with a pleasing texture that feels light rather than sticky.
Who Can Use Pei-1500
Pei-1500 is generally considered suitable for all skin types including oily, dry, combination and sensitive because it is inert and used at very low levels that do not tend to upset the skin’s barrier. Those with extremely reactive or allergy-prone skin may still prefer to monitor any new product closely since even gentle polymers can occasionally trigger irritation when other actives are present.
The ingredient is entirely synthetic with no animal-derived inputs so it aligns with vegan and vegetarian preferences.
Current safety data indicate no specific risks for pregnant or breastfeeding women. That said this information is not medical advice and anyone who is expecting or nursing should review their routine with a qualified healthcare provider to be extra safe.
Pei-1500 does not increase photosensitivity, so it will not make skin more prone to sunburn. It is odorless, colorless and compatible with both fragrance-free and fragranced products which makes it versatile for daily use.
Potential Side Effects/Adverse Reactions
Individual responses to topical Pei-1500 can differ. The effects listed below are only potential outcomes and are not expected for the average user when the ingredient is properly formulated.
- Mild skin redness or itching
- Transient stinging on very compromised or freshly exfoliated skin
- Allergic contact dermatitis in those already sensitized to polyamines
- Eye irritation if the product accidentally splashes into the eyes
If any of these effects occur stop using the product and consult a healthcare professional for guidance.
Comedogenic Rating
Rating: 0 / 5
Pei-1500 is a large water-soluble polymer used at very low concentrations, so it stays on the surface then rinses or wears away without penetrating or mixing with skin oils. Because it neither forms an occlusive film nor adds extra oil, it has virtually no tendency to block pores.
This makes it suitable for people who are prone to acne or breakouts.
Keep in mind that a product’s overall pore-clogging potential depends on the full formula. Even if Pei-1500 scores a zero, heavier emollients or waxes in the same product could still be an issue.
Summary
Pei-1500 is a synthetic aziridine homopolymer that acts as a viscosity controller. By swelling in water it fine-tunes thickness, keeps actives evenly suspended and creates a smooth glide without adding weight or greasiness.
While not a household name, it shows up in many modern lightweight cleansers, serums and masks because formulators appreciate its reliable performance and compatibility with a wide range of ingredients.
Current data classify Pei-1500 as low risk for irritation, sensitization or comedogenicity when used as directed. Still, skin is personal, so it is wise to patch test any new product that contains this or any other unfamiliar ingredient.