Ingredient review
Polyquaternium-31
INCI: Polyquaternium-31
A gentle synthetic polymer that smooths hair and skin without heavy buildup, making it a popular choice for sensitive scalps and fine hair.
In plain English
Polyquaternium-31 is a man-made ingredient that forms a thin, flexible film on hair or skin. This film helps reduce frizz, adds slip, and makes hair easier to comb when wet. It also helps other ingredients spread more evenly. Unlike some older conditioning agents, it is less likely to cause buildup or weigh hair down, so it works well for fine or low-porosity hair. In skincare, it can make lotions feel silkier without leaving a sticky residue.
Review score
Safety, usefulness, and evidence
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
Quick decision guide
Useful, but context matters
Polyquaternium-31 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.
- Step 1Start with the score, then check the irritation and clogging risk before judging Polyquaternium-31.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- 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
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A cationic (positively charged) polymer belonging to the polyquaternium family. It is synthesized from acrylic acid and other monomers, designed to bind to negatively charged surfaces like hair and skin.
How it works
Its positive charge attracts it to the negative charge of damaged hair or skin, forming a smooth, protective film. This film reduces static electricity, improves wet combing, and gives a soft, conditioned feel. In skincare, it helps other ingredients stay on the skin longer and improves the sensory feel of the product.
Pros
Lightweight conditioning
Unlike heavier silicones or oils, Polyquaternium-31 provides slip and softness without making fine hair feel greasy or limp.
Low irritation potential
It is considered very gentle on skin and scalp, making it suitable for sensitive skin and frequent use.
Cons and cautions
Potential buildup over time
While lighter than many alternatives, repeated use without clarifying shampoo can still lead to minor residue on very fine or low-porosity hair.
Synthetic origin
It is not naturally derived, which may be a concern for those seeking exclusively natural or biodegradable ingredients.
Best for
- People with fine or easily weighed-down hair
- Those looking for a gentle, low-irritation conditioner
Use caution if
- Individuals with known sensitivity to synthetic polymers (rare)
Usage tips
Safety summary
Polyquaternium-31 has a strong safety profile with very low irritation and sensitization potential. It is considered safe for use in rinse-off and leave-on products at typical concentrations.
Research notes
Studies on polyquaternium polymers generally show good skin and eye tolerability. Specific data on Polyquaternium-31 is limited, but its chemical class is well-documented and accepted by cosmetic safety panels.
Common label clues
- Typical concentration
- 0.1% to 2%
- Regulatory status
- Approved for cosmetic use in the EU, US, and most major markets. No known restrictions at typical use levels.
- Common uses
- Conditioners, Leave-in treatments, Styling products, Shampoos, Body washes
- Environmental note
- As a synthetic polymer, it is not readily biodegradable. However, its low use concentration and rinse-off nature limit environmental impact compared to microplastics.
Good to know
- Polyquaternium-31 is often combined with other conditioning agents to balance slip and hold.
- It is compatible with both sulfate and sulfate-free cleansers.
Common questions
What is Polyquaternium-31 in beauty products?
Polyquaternium-31 is a man-made ingredient that forms a thin, flexible film on hair or skin. This film helps reduce frizz, adds slip, and makes hair easier to comb when wet. It also helps other ingredients spread more evenly. Unlike some older conditioning agents, it is less likely to cause buildup or weigh hair down, so it works well for fine or low-porosity hair. In skincare, it can make lotions feel silkier without leaving a sticky residue.
What does Polyquaternium-31 do in a beauty product?
Its positive charge attracts it to the negative charge of damaged hair or skin, forming a smooth, protective film. This film reduces static electricity, improves wet combing, and gives a soft, conditioned feel. In skincare, it helps other ingredients stay on the skin longer and improves the sensory feel of the product.
Is Polyquaternium-31 safe for most people?
Polyquaternium-31 has a strong safety profile with very low irritation and sensitization potential. It is considered safe for use in rinse-off and leave-on products at typical concentrations.
Who should be careful with Polyquaternium-31?
Individuals with known sensitivity to synthetic polymers (rare)
Research sources
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.