What Is Pei-1400?
Pei-1400 is the cosmetic trade name for a synthetic polymer technically known as aziridine homopolymer, more commonly called polyethyleneimine. It is created in a lab by opening tiny three-membered aziridine rings and linking them into a long branching chain. The result is a clear to pale yellow liquid or semi solid with a strong ability to thicken water-based mixtures.
The material was first developed in the 1940s for paper and water treatment. Formulators soon noticed its knack for controlling texture, so by the late 20th century it began appearing in personal care products where a smooth, stable feel was needed.
Production starts with purified aziridine derived from ethylene. Under carefully controlled heat, pressure and catalysts, the monomer molecules join to form polymer chains averaging about 1 400 molecular weight units, hence the name Pei-1400. After polymerization the mixture is neutralized, filtered and standardized for cosmetic use.
Today Pei-1400 can be found in a range of leave-on and rinse-off products such as facial creams, serums, peel-off masks, hair gels, mascaras and sunscreens. It is prized for its ability to keep formulas from separating while giving them a pleasant, non-sticky thickness.
Pei-1400’s Cosmetic Benefits/Uses
In cosmetics Pei-1400 serves one main purpose: viscosity controlling. By binding water and forming a lightweight network it increases the thickness of lotions, gels and creams. This ensures the product spreads evenly, stays where you apply it and feels more luxurious. It also helps suspend pigments or actives evenly throughout the formula, so every use delivers consistent results.
Who Can Use Pei-1400
Pei-1400 is generally well tolerated by most skin types including normal, dry, oily and combination skin. People with very sensitive or compromised skin should approach cautiously because the polymer’s amine groups can occasionally trigger mild irritation in reactive complexions.
The ingredient is synthetic and sourced from petrochemical feedstocks, so it contains no animal-derived substances. This makes products using Pei-1400 suitable for both vegetarians and vegans, assuming the finished formula has not been tested on animals.
Current data show no evidence that Pei-1400 penetrates deeply enough to pose a risk during pregnancy or while breastfeeding. That said this is not medical advice and anyone who is pregnant or nursing should check with a doctor before adding a new skincare product to their routine.
Pei-1400 does not absorb UV light and is not known to cause photosensitivity. It can be worn day or night without increasing sun sensitivity.
Potential Side Effects/Adverse Reactions
Responses to topical Pei-1400 differ from person to person. The points below outline potential side effects, yet most users experience none if the product has been formulated correctly.
- Mild skin irritation – fleeting stinging or burning can appear, especially on sensitive skin
- Redness or flushing – temporary pinkness where the product was applied
- Itching – light pruritus that usually subsides once the product is removed
- Allergic contact dermatitis – rare delayed reaction with swelling or rash in those sensitized to polyethyleneimine
- Eye irritation – tearing or discomfort if the ingredient accidentally enters the eyes
If any of these effects occur stop using the product and consult a healthcare professional for advice.
Comedogenic Rating
Pei-1400 earns a comedogenic rating of 0. It is a water-soluble polymer that stays on the surface of the skin, adds thickness and then rinses or wears away without leaving an oily film that could block pores. Because it does not contain heavy oils or waxes and is used at low levels, it is very unlikely to contribute to blackheads or pimples.
That means Pei-1400 is generally suitable for people who are prone to acne or breakouts.
One extra note: if a formula also contains rich emollients or butters, the overall product could still feel heavy even though Pei-1400 itself is non-comedogenic, so always consider the full ingredient list.
Summary
Pei-1400 is mainly a texture helper. By binding to water and forming a light web, it thickens lotions and gels so they spread smoothly, stay mixed and feel more luxurious on skin or hair. It is not a blockbuster active so it is less well-known than buzzier ingredients, but chemists value its reliability and cost-effectiveness, so you will spot it in a fair number of creams, masks and styling products.
Current research shows Pei-1400 to be low risk with only occasional mild irritation reported, especially on very sensitive skin. When trying any new product that contains it, give yourself extra peace of mind by doing a quick patch test first.