Ingredient review
C11-15 Pareth-9
INCI: C11-15 Pareth-9
A gentle cleansing agent that helps remove dirt and oil without stripping the skin, but may cause irritation for very sensitive skin types.
In plain English
C11-15 Pareth-9 is a synthetic ingredient that helps water and oil mix together, so your cleanser can effectively remove makeup, sunscreen, and excess oil. It's a type of surfactant (a fancy word for a cleansing agent) that creates a light foam and rinses off easily. While it's considered milder than some older surfactants, it can still be drying or irritating for people with very sensitive or compromised skin.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Main practical flags: irritation is moderate; clogging risk is low.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- moderate
- Clogging risk
- low
Quick decision guide
Useful, but context matters
C11-15 Pareth-9 can be useful, but watch for some irritation potential.
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 C11-15 Pareth-9.
- 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
moderateCan bother some users, especially with frequent use, damaged skin, or strong companion ingredients.
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
C11-15 Pareth-9 is a synthetic surfactant made from a blend of fatty alcohols (C11-15) that have been reacted with ethylene oxide to create a water-soluble cleansing molecule. It belongs to the 'pareth' family of ethoxylated alcohols, which are widely used in personal care products for their ability to reduce surface tension and help remove dirt and oil.
How it works
In a cosmetic product, C11-15 Pareth-9 works by lowering the surface tension between water and oil, allowing them to mix. This helps break down sebum, sunscreen, and makeup so they can be rinsed away with water. It also helps stabilize emulsions (like lotions and creams) so the oil and water phases don't separate.
Pros
Effective cleanser
Removes oil, sunscreen, and makeup without heavy scrubbing, making it practical for daily use.
Rinses cleanly
Does not leave a greasy residue, so your skin feels fresh after washing.
Cons and cautions
Potential irritation
For sensitive or damaged skin, this surfactant can cause stinging, redness, or dryness, especially with frequent use.
Ethoxylation concerns
The manufacturing process can create trace amounts of 1,4-dioxane, a possible carcinogen, though reputable brands purify their ingredients to minimize this.
Best for
- People with normal to oily skin looking for a gentle cleanser
- Those who wear light makeup or sunscreen and need effective removal
Use caution if
- Individuals with very dry, compromised, or eczema-prone skin
- Anyone with a known sensitivity to ethoxylated ingredients
Usage tips
Safety summary
C11-15 Pareth-9 is generally considered safe for use in rinse-off products at typical concentrations. The main concern is potential skin irritation for sensitive individuals and trace contamination with 1,4-dioxane, which is regulated in many countries. Reputable manufacturers purify their ingredients to keep 1,4-dioxane levels very low.
Research notes
Studies on ethoxylated alcohols indicate low acute toxicity and moderate skin irritation potential. The Cosmetic Ingredient Review (CIR) panel has reviewed similar pareth ingredients and found them safe for use in cosmetics when formulated properly. Research on 1,4-dioxane contamination has led to industry-wide purification standards.
Common label clues
- Typical concentration
- 1% to 10% depending on product type
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions, with concentration limits for 1,4-dioxane in some markets.
- Common uses
- Cleansers, Shampoos, Body washes, Facial washes, Makeup removers
- Environmental note
- As a synthetic ethoxylate, it may not be readily biodegradable in all conditions, though many modern formulations use biodegradable alternatives.
Good to know
- C11-15 Pareth-9 is often used in combination with other mild surfactants to reduce irritation potential.
- The number '9' refers to the average number of ethylene oxide units, which affects how water-soluble and mild the ingredient is.
Common questions
What is C11-15 Pareth-9 in beauty products?
C11-15 Pareth-9 is a synthetic ingredient that helps water and oil mix together, so your cleanser can effectively remove makeup, sunscreen, and excess oil. It's a type of surfactant (a fancy word for a cleansing agent) that creates a light foam and rinses off easily. While it's considered milder than some older surfactants, it can still be drying or irritating for people with very sensitive or compromised skin.
What does C11-15 Pareth-9 do in a beauty product?
In a cosmetic product, C11-15 Pareth-9 works by lowering the surface tension between water and oil, allowing them to mix. This helps break down sebum, sunscreen, and makeup so they can be rinsed away with water. It also helps stabilize emulsions (like lotions and creams) so the oil and water phases don't separate.
Is C11-15 Pareth-9 safe for most people?
C11-15 Pareth-9 is generally considered safe for use in rinse-off products at typical concentrations. The main concern is potential skin irritation for sensitive individuals and trace contamination with 1,4-dioxane, which is regulated in many countries. Reputable manufacturers purify their ingredients to keep 1,4-dioxane levels very low.
Who should be careful with C11-15 Pareth-9?
Individuals with very dry, compromised, or eczema-prone skin Anyone with a known sensitivity to ethoxylated ingredients
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.