What Is Polyquaternium-105?
Polyquaternium-105 is a man-made polymer classified as a quaternary ammonium compound. It forms when three building blocks—phosphorylcholine glycol methacrylate, acrylamidopropyltrimonium chloride and stearyl methacrylate—are combined through controlled polymerization. The result is a large, positively charged molecule that easily bonds to hair fibers.
This ingredient grew out of research in the late 1990s that looked for gentler alternatives to older cationic conditioners. Chemists discovered that adding a phosphorylcholine group, which imitates components of cell membranes, gave the polymer a softer feel and better compatibility with the scalp. Since then formulators have adopted Polyquaternium-105 in a variety of rinse-off and leave-on products because of its strong affinity for keratin.
Production starts with individual monomers that are purified, mixed in precise ratios then triggered to react under heat or ultraviolet light. After polymerization, the viscous solution is neutralized, filtered and dried into flakes or supplied as a liquid concentrate to manufacturers.
You’ll most often spot Polyquaternium-105 in shampoos, conditioners, hair masks, leave-in creams, styling gels and anti-frizz serums where smoothness and slip are key selling points.
Polyquaternium-105’s Cosmetic Benefits/Uses
Polyquaternium-105 is primarily valued for one core function in hair care formulations.
Hair conditioning: The positive charge of Polyquaternium-105 attaches to the negatively charged sites along damaged hair cuticles, forming a thin, even film. This film reduces static, improves detangling, boosts softness and imparts a healthy-looking shine. Because the polymer resists rinsing, these benefits last through multiple washes which helps maintain style and manageability.
Who Can Use Polyquaternium-105
Polyquaternium-105 is generally suitable for all scalp and hair types including normal, dry, oily and color-treated strands because its lightweight cationic film bonds where damage exists without clogging follicles. Those with very sensitive skin or chronic scalp conditions such as eczema may still want to monitor tolerance since any film-forming polymer can occasionally trap irritants close to the skin.
The molecule is fully synthetic and contains no animal-derived raw materials so it is compatible with vegan and vegetarian lifestyles. As always, certification depends on the finished product’s entire formula and the brand’s stance on animal testing.
No specific warnings exist for pregnancy or breastfeeding. Available safety data shows the ingredient stays on the hair surface rather than penetrating skin but this is not medical advice. Expectant or nursing individuals should consult a healthcare professional before introducing new personal care products just to be sure.
Polyquaternium-105 does not increase photosensitivity and it is stable under normal daylight. It is also free of common allergens like gluten or nuts which makes it an easy fit for most consumer preferences.
Potential Side Effects/Adverse Reactions
Individual responses to topical Polyquaternium-105 can differ. The points below outline possible but uncommon reactions when the ingredient is used in properly formulated hair products.
- Scalp itching or mild redness
- Allergic contact dermatitis in people sensitized to quaternary ammonium compounds
- Eye irritation if shampoo or conditioner runs into the eyes
- Product buildup leading to limp or greasy-feeling hair when used in very high concentrations or without thorough cleansing
If any of these effects occur discontinue use and seek medical advice if symptoms persist or worsen.
Comedogenic Rating
Rating: 0-1 (non-comedogenic to very low)
Polyquaternium-105 is a large, water-soluble polymer that stays mostly on the surface of hair shafts then rinses away during cleansing. Its molecular size prevents it from slipping into follicles where breakouts start, and it is not an oil or fatty acid that would occlude pores. For these reasons it earns a 0-1 on the comedogenic scale.
Suitable for acne-prone or breakout-prone users in leave-on and rinse-off hair products.
Because most formulas containing Polyquaternium-105 are applied to hair rather than facial skin, the likelihood of pore blockage on the face is even lower. Any residue that drips onto the skin during rinsing is highly diluted by water.
Summary
Polyquaternium-105 is a synthetic quaternary polymer used mainly as a hair conditioner. Its positive charge binds to negatively charged damaged cuticles, forming a thin film that smooths, detangles, reduces static and leaves hair softer with added shine. The film resists rinse-off which keeps hair manageable between washes.
While not a household name, the ingredient appears in a fair number of modern shampoos, conditioners and styling creams where lightweight conditioning is needed without heavy oils.
Current safety data shows low irritation potential, minimal skin penetration and virtually no comedogenicity. As with any new personal care ingredient it is wise to perform a small patch test when trying a fresh product to confirm individual compatibility.