What Is C9-11 Pareth-6 Carboxylic Acid?
C9-11 Pareth-6 Carboxylic Acid is a synthetic ingredient made from medium chain fatty alcohols with 9 to 11 carbon atoms that have been chemically linked to about six units of ethylene oxide, then converted to a mild carboxylic acid. This gives the molecule both oil loving and water loving parts, which makes it an effective surfactant. The material was first explored in the late twentieth century when formulators were searching for gentler alternatives to traditional sulfates. By adjusting the length of the fatty chain and the number of ethylene oxide units, chemists created a cleanser that lifts dirt and oil without over stripping the skin.
Production starts with plant derived or petroleum based fatty alcohols. These are reacted with ethylene oxide in a controlled setting to add the oxyethylene groups. A final oxidation step introduces the carboxylic acid head that improves water solubility. The finished ingredient is usually supplied as a clear to pale yellow liquid or paste.
You will most often find C9-11 Pareth-6 Carboxylic Acid in facial cleansers, body washes, micellar waters, liquid hand soaps, baby washes, makeup removers and some exfoliating pads. Its mild nature and good foaming profile make it suitable for sensitive skin formulas as well as daily use products.
C9-11 Pareth-6 Carboxylic Acid’s Cosmetic Benefits/Uses
This ingredient plays a key role in wash off products.
Cleansing: The dual nature of the molecule surrounds oil based grime, makeup and excess sebum, allowing them to mix with water and rinse away. Compared with harsher detergents it offers a softer skin feel, stable foam and reduced chance of irritation, which can help a formula earn “gentle cleanser” claims.
Who Can Use C9-11 Pareth-6 Carboxylic Acid
This mild surfactant works well for most skin types, including oily, dry, combination and sensitive skin. Because it cleanses without stripping, even reactive or redness-prone complexions usually tolerate it. Extremely dry or compromised skin might still prefer a richer cleanser, but the ingredient itself is not known to worsen such conditions.
The raw materials come from plant or petroleum sources and contain no animal derivatives, so products using C9-11 Pareth-6 Carboxylic Acid are generally suitable for vegans and vegetarians. If a brand markets a fully vegan formula, it should confirm that no animal-based processing aids were used along the supply chain.
No data suggest any specific risk for pregnant or breastfeeding women when the ingredient is used in rinse-off products. This is not medical advice, and anyone who is expecting or nursing should show their skincare lineup to a healthcare professional for personalized guidance.
C9-11 Pareth-6 Carboxylic Acid does not make skin more sensitive to sunlight, so there is no added need for extra sun precautions beyond everyday SPF use.
Potential Side Effects/Adverse Reactions
Responses to topical ingredients differ from person to person. The points below represent possible but uncommon effects when C9-11 Pareth-6 Carboxylic Acid is used as intended in cosmetic products. Most users experience none of these issues.
- Transient dryness or tightness in individuals with very low sebum levels
- Mild stinging or redness on highly sensitive or compromised skin barriers
- Eye irritation if the cleanser accidentally gets into the eyes
- Allergic contact dermatitis in the rare case of an individual sensitivity to this specific surfactant family
If any discomfort, persistent redness or swelling occurs stop using the product and consult a qualified medical professional.
Comedogenic Rating
Rating: 1/5. C9-11 Pareth-6 Carboxylic Acid is a water-soluble surfactant that rinses off cleanly and leaves behind little to no residue, so it poses minimal risk of clogging pores. Its fatty chain length is short to medium and balanced by several hydrophilic oxyethylene units, further lowering any occlusive potential.
Because of this low score the ingredient is generally fine for people who are prone to acne or breakouts, especially in rinse-off products where contact time is brief.
As with any cleanser the overall formula matters more than one component. Heavy oils, waxes or leave-on actives paired with it could still trigger congestion for some users.
Summary
C9-11 Pareth-6 Carboxylic Acid is a mild cleansing agent that works by surrounding dirt, oil and makeup so they can be lifted away with water. Its balanced oil-loving and water-loving structure lets it create a gentle yet stable foam while respecting the skin barrier.
Although not as famous as sulfates or newer plant-based glucosides it appears in a steady stream of facial cleansers, body washes and makeup removers aimed at consumers seeking kinder alternatives to harsher detergents.
Current safety data and real-world use show a very low risk of irritation or pore blockage when the ingredient is used in rinse-off formulas. Still, everyone’s skin is unique so it is smart to patch test any new product containing C9-11 Pareth-6 Carboxylic Acid before making it a staple.