What Is Polyquaternium-31?
Polyquaternium-31 is a synthetic, water-soluble polymer created by first polymerizing acrylonitrile, then partially hydrolyzing the chains and finally reacting them with 3-dimethylaminopropylamine followed by quaternization with dimethyl sulfate. The result is a cationic molecule that carries a positive charge, allowing it to bond easily with the negatively charged surface of hair and skin.
The material was introduced to the beauty industry in the late 1970s as formulators searched for milder alternatives to traditional conditioning agents. Its strong yet flexible film-forming ability and antistatic action quickly made it popular in both haircare and skincare lines.
Manufacturing starts with an aqueous acrylonitrile solution that undergoes controlled polymerization. After hydrolysis and amine treatment, the polymer is quaternized, filtered and dried or supplied as a concentrated liquid. This production route gives a consistent molecular weight range, which helps brands maintain batch-to-batch performance.
Today Polyquaternium-31 can be spotted in a wide range of products including shampoos, rinse-off and leave-in conditioners, anti-frizz sprays, styling gels, mousses, hair masks, skin creams, lightweight lotions, sheet masks and hydrating serums.
Polyquaternium-31’s Cosmetic Benefits/Uses
Formulators rely on Polyquaternium-31 for two main reasons:
- Antistatic: Its positive charge neutralizes the static buildup that makes hair flyaway or causes skin discomfort in low-humidity settings. This leads to smoother strands, easier comb-through and a sleeker finish after styling.
- Film Forming: The polymer lays down a thin, flexible coating that locks in moisture, boosts shine and provides light hold. On hair it adds body and definition while protecting against environmental stress. On skin it leaves a soft, conditioned feel and helps active ingredients stay in place for longer wear.
Who Can Use Polyquaternium-31
Polyquaternium-31 is generally well tolerated by all skin and hair types. Its light film sits comfortably on oily, normal and dry skin without feeling greasy or heavy. People with very sensitive or eczema-prone skin might want to watch for any tightness or redness because the ingredient’s positive charge can occasionally feel a bit clingy on already irritated skin.
The polymer is made entirely from synthetic, non-animal raw materials so it fits the needs of vegans and vegetarians.
No specific warnings exist for pregnant or breastfeeding women. That said this is not medical advice. Anyone who is expecting or nursing should check with a healthcare professional before adding new products to their routine.
Polyquaternium-31 does not make skin more sensitive to sunlight and it has no known effect on self-tanning or SPF formulas.
Potential Side Effects/Adverse Reactions
Reactions to topical Polyquaternium-31 vary from person to person. The points below list potential but uncommon side effects. When used at the levels found in properly formulated cosmetics most users will not experience any of these issues.
- Temporary itching or redness
- Mild stinging on already broken or inflamed skin
- Build-up on hair if shampooing is not thorough which may lead to dullness or limp strands
- Eye irritation if the product accidentally gets into the eyes
If any discomfort or irritation occurs stop use immediately and consult a healthcare professional if symptoms persist.
Comedogenic Rating
Rating: 1 / 5
Polyquaternium-31 is water soluble and forms a breathable, ultrathin film that rinses off easily, so it is very unlikely to block pores. The small chance of residue build-up in heavy leave-on formulas keeps it from getting a perfect zero.
Suitable for acne-prone or breakout-prone skin in most cases.
Because the ingredient carries a positive charge it can bind to skin proteins; overuse without proper cleansing could, in theory, trap debris on very oily skin though real-world reports of this are rare.
Summary
Polyquaternium-31 works as an antistatic and film-forming agent by virtue of its cationic backbone, which clings to the negatively charged surface of hair and skin. This creates a smooth, moisture-locking layer that tames static, adds light hold, boosts shine and leaves skin feeling conditioned.
While it has never reached superstar status, the polymer enjoys steady popularity in shampoos, conditioners, styling sprays and an increasing number of lightweight lotions and serums thanks to its reliable performance and gentle feel.
Current safety data show a low risk of irritation or sensitization when used at cosmetic levels. As with any new product, give your skin or scalp a quick patch test first to confirm personal compatibility.