Ingredient review
C9-11 Pareth-6 Carboxylic Acid
INCI: C9-11 PARETH-6 CARBOXYLIC ACID
A gentle, semi-synthetic surfactant that effectively cleanses without over-drying, making it a good choice for sensitive or dry skin.
In plain English
This ingredient is a mild cleansing agent that helps water mix with oil and dirt so they can be rinsed away. It is made from a blend of fatty alcohols (from plant or synthetic sources) and ethylene oxide, then modified to be less irritating than traditional soaps. Because it is gentle, it is often used in products for sensitive or dry 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.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- semi synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
C9-11 Pareth-6 Carboxylic Acid 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 C9-11 Pareth-6 Carboxylic Acid.
- 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
C9-11 Pareth-6 Carboxylic Acid is a semi-synthetic surfactant and emulsifier. It belongs to the alkyl ether carboxylic acid family, which are known for being mild and compatible with other cleansing ingredients.
How it works
It reduces the surface tension between water and oil, allowing impurities to be lifted from the skin and rinsed away. Its carboxylic acid group gives it a slightly acidic pH, which helps maintain the skin's natural acid mantle and reduces irritation.
Pros
Gentle on skin
Its mild cleansing action helps remove dirt and oil without stripping the skin's natural moisture barrier, making it suitable for daily use on sensitive or dry skin.
pH-friendly
The carboxylic acid group helps keep the product's pH close to the skin's natural level (around 5.5), which can reduce irritation and support a healthy skin barrier.
Cons and cautions
Potential for slight dryness
In high concentrations or in leave-on products, it may still cause some dryness or tightness, especially for very dry or compromised skin.
Semi-synthetic origin
Because it is made through ethoxylation, some consumers prefer plant-derived or fully natural alternatives, though it is generally considered safe.
Best for
- People with sensitive or easily irritated skin
- Those looking for a sulfate-free or gentle cleanser
Use caution if
- Individuals with known allergies to ethoxylated ingredients (rare)
Usage tips
Safety summary
C9-11 Pareth-6 Carboxylic Acid is considered safe for use in cosmetics at typical concentrations. It has low irritation and sensitization potential, though individuals with very sensitive skin should patch-test new products.
Research notes
Alkyl ether carboxylic acids like this one are well-studied as mild surfactants. Research supports their low irritation profile and compatibility with skin's pH. No significant safety concerns have been raised by regulatory bodies.
Common label clues
- Typical concentration
- 1–10% in rinse-off products; lower in leave-on formulas
- Regulatory status
- Approved for use in cosmetics in the EU, US, and other major markets. Generally recognized as safe when used as directed.
- Common uses
- Cleansers, Facial washes, Shampoos, Body washes, Makeup removers
- Environmental note
- Ethoxylated surfactants may have moderate biodegradability; however, C9-11 Pareth-6 Carboxylic Acid is generally considered less persistent than some other ethoxylates.
Good to know
- This ingredient is often used alongside other mild surfactants to create a balanced cleansing formula.
- It is considered biodegradable and is not classified as a known irritant by major cosmetic safety panels.
Common questions
What is C9-11 Pareth-6 Carboxylic Acid in beauty products?
This ingredient is a mild cleansing agent that helps water mix with oil and dirt so they can be rinsed away. It is made from a blend of fatty alcohols (from plant or synthetic sources) and ethylene oxide, then modified to be less irritating than traditional soaps. Because it is gentle, it is often used in products for sensitive or dry skin.
What does C9-11 Pareth-6 Carboxylic Acid do in a beauty product?
It reduces the surface tension between water and oil, allowing impurities to be lifted from the skin and rinsed away. Its carboxylic acid group gives it a slightly acidic pH, which helps maintain the skin's natural acid mantle and reduces irritation.
Is C9-11 Pareth-6 Carboxylic Acid safe for most people?
C9-11 Pareth-6 Carboxylic Acid is considered safe for use in cosmetics at typical concentrations. It has low irritation and sensitization potential, though individuals with very sensitive skin should patch-test new products.
Who should be careful with C9-11 Pareth-6 Carboxylic Acid?
Individuals with known allergies to ethoxylated ingredients (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.