Ingredient review

Polyquaternium-105

INCI: Polyquaternium-105

Polyquaternium-105 is a gentle conditioning polymer that helps reduce frizz and static in hair while improving product spreadability, with a low risk of irritation.

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In plain English

Polyquaternium-105 is a type of positively charged polymer (a long-chain molecule) that sticks to the negatively charged surfaces of hair and skin. In hair products, it forms a thin, flexible film that smooths the hair cuticle, reduces static electricity (flyaways), and makes hair feel softer and easier to comb. In skincare, it can improve the feel of a product on the skin and help other ingredients spread evenly. Because it is water-soluble and does not build up heavily, it rinses off easily and is generally well-tolerated.

Review score

Safety, usefulness, and evidence

3.8Good
3.8/ 5

Potentially useful with some tradeoffs

The evidence base is useful, but some claims depend heavily on the formula.

Risk flags are low for most users, though the finished product can still irritate.

Source
synthetic
Evidence
moderate
Irritation
low
Clogging risk
low
How reviews are scored

Quick decision guide

Useful, but context matters

Polyquaternium-105 is generally a lower-concern ingredient when the full formula suits your skin.

Plain-English read

Treat this as a practical screening step before you compare products that contain this ingredient.

  1. Step 1Start with the score, then check the irritation and clogging risk before judging Polyquaternium-105.
  2. Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
  3. Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.

Score terms in plain English

Irritation risk

low

Less likely to sting, burn, or bother most users, though sensitive skin can still react.

Clogging risk

low

Less likely to feel heavy or contribute to clogged pores for most skin types.

Evidence level

moderate

There is useful support, but formula details and claim strength still matter.

What it is

Polyquaternium-105 is a synthetic, water-soluble cationic polymer belonging to the polyquaternium family. It is designed to provide conditioning and antistatic benefits without leaving a heavy or greasy residue.

How it works

Its positive charge allows it to electrostatically bind to the negatively charged surfaces of hair and skin. Once bound, it forms a thin, flexible film that smooths the cuticle, reduces friction, and neutralizes static charge. This film also helps other ingredients (like oils or humectants) adhere better, improving overall product performance.

Pros

Lightweight conditioning

Provides noticeable softness and detangling without the heavy, greasy feel of some oils or silicones, making it suitable for fine or normal hair.

Low irritation potential

Rated low for both irritation and comedogenicity, so it is generally safe for sensitive skin and won't clog pores in most people.

Cons and cautions

Possible buildup on fine hair

With repeated use, especially in leave-in products, it may accumulate on very fine or low-porosity hair, leading to dullness or limpness.

Limited environmental data

While considered safe at typical use levels, comprehensive long-term biodegradability studies are not widely published, so its full environmental impact is not fully known.

Best for

  • People with frizzy or static-prone hair looking for lightweight conditioning
  • Those who want a gentle, non-irritating polymer for sensitive skin or scalp

Use caution if

  • Individuals with very fine, low-porosity hair who experience buildup from any polymer

Usage tips

Use in rinse-off products (shampoos, conditioners) to minimize buildup on fine hair.
If using a leave-in product with Polyquaternium-105, clarify your hair every few weeks with a gentle sulfate-free clarifying shampoo.
Pair with a humectant like glycerin to balance moisture and prevent the polymer from feeling too film-like.

Safety summary

Polyquaternium-105 is considered safe for use in cosmetics at typical concentrations. It has low irritation and comedogenic potential, making it suitable for sensitive skin and most hair types. No significant safety concerns have been raised by regulatory bodies.

Research notes

Research on polyquaterniums in general shows they are effective conditioning agents with low toxicity. Specific studies on Polyquaternium-105 are limited, but its chemical structure and properties are well understood and consistent with other safe polyquaterniums.

Common label clues

Typical concentration
0.1% to 2%
Regulatory status
Approved for use in cosmetics in the EU, US, and most major markets. No specific concentration restrictions, but typical use is below 2%.
Common uses
Conditioners, Shampoos, Leave-in treatments, Styling products, Body washes
Environmental note
Polyquaternium-105 is not readily biodegradable, but its low use concentration and high water solubility reduce the risk of bioaccumulation. Wastewater treatment can remove a significant portion.

Good to know

  • Polyquaternium-105 is often chosen for its low molecular weight, which allows it to penetrate the hair cuticle slightly for deeper conditioning.
  • It is compatible with anionic surfactants (like sodium lauryl sulfate) and can be used in clear formulas without cloudiness.

Common questions

What is Polyquaternium-105 in beauty products?

Polyquaternium-105 is a type of positively charged polymer (a long-chain molecule) that sticks to the negatively charged surfaces of hair and skin. In hair products, it forms a thin, flexible film that smooths the hair cuticle, reduces static electricity (flyaways), and makes hair feel softer and easier to comb. In skincare, it can improve the feel of a product on the skin and help other ingredients spread evenly. Because it is water-soluble and does not build up heavily, it rinses off easily and is generally well-tolerated.

What does Polyquaternium-105 do in a beauty product?

Its positive charge allows it to electrostatically bind to the negatively charged surfaces of hair and skin. Once bound, it forms a thin, flexible film that smooths the cuticle, reduces friction, and neutralizes static charge. This film also helps other ingredients (like oils or humectants) adhere better, improving overall product performance.

Is Polyquaternium-105 safe for most people?

Polyquaternium-105 is considered safe for use in cosmetics at typical concentrations. It has low irritation and comedogenic potential, making it suitable for sensitive skin and most hair types. No significant safety concerns have been raised by regulatory bodies.

Who should be careful with Polyquaternium-105?

Individuals with very fine, low-porosity hair who experience buildup from any polymer

Research sources

Cosmetic Ingredient Review (CIR) - Safety Assessment of PolyquaterniumsOpenPubChem - Polyquaternium-105OpenEuropean Chemicals Agency (ECHA) - Polyquaternium-105Open

Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.