What Is C9-11 Alketh-8 Carboxylic Acid?
C9-11 Alketh-8 Carboxylic Acid is a synthetic surfactant created from a blend of coconut and petroleum-derived fatty alcohols that contain nine to eleven carbon atoms. These alcohols are first reacted with about eight units of ethylene oxide to form an ethoxylated chain, then the terminal end is converted into a carboxylic acid. The result is a molecule that has both water-loving and oil-loving parts, making it highly effective at lifting dirt and oil from skin or hair.
Nonionic surfactants like this one became popular in the cosmetics industry during the 1960s when formulators looked for milder alternatives to traditional soaps. Over time chemists refined the process to improve stability and reduce irritation, leading to the version commonly used today.
Production usually starts with fractionated natural or synthetic C9-11 alcohols. These alcohols undergo controlled ethoxylation in the presence of a catalyst, followed by carboxylation through oxidation or reaction with chloroacetic acid. The finished material is a clear to slightly hazy liquid that blends easily into water-based systems.
You will most often see C9-11 Alketh-8 Carboxylic Acid in facial cleansers, body washes, shampoos, micellar waters and makeup removers. It can also show up in exfoliating scrubs and sheet mask essences where gentle yet thorough cleansing is needed without stripping the skin.
C9-11 Alketh-8 Carboxylic Acid’s Cosmetic Benefits/Uses
Formulators turn to this ingredient mainly for one key reason.
Cleansing: Its balanced hydrophilic and lipophilic structure allows it to surround oils, makeup and everyday grime so they can be rinsed away with water. Because it is nonionic, it tends to be milder than many sulfated surfactants which helps minimize tightness or dryness after washing.
Who Can Use C9-11 Alketh-8 Carboxylic Acid
This surfactant is generally well tolerated by most skin types including normal, oily, combination and even sensitive skin because its nonionic nature keeps it mild and less likely to disturb the skin barrier. Very dry or compromised skin may still prefer richer cleansers that leave behind more lipids but C9-11 Alketh-8 Carboxylic Acid itself is not known to be inherently drying when formulated correctly.
The ingredient is synthesized from plant sourced or petroleum based fatty alcohols and does not rely on animal by-products, so it is suitable for vegans and vegetarians. As always, finished products should be checked for other animal derived ingredients if strict adherence is required.
There is no evidence that topical use poses specific risks to pregnant or breastfeeding women. That said this is not medical advice and anyone who is expecting or nursing should show the full ingredient list of any skincare product to their health care provider just to be safe.
C9-11 Alketh-8 Carboxylic Acid does not make skin more sensitive to sunlight and has no known interactions with common photosensitizing medications. It is fragrance free by nature and unlikely to mask or amplify the scent of other ingredients, which can be helpful for those avoiding strong smells.
Potential Side Effects/Adverse Reactions
Responses to topical C9-11 Alketh-8 Carboxylic Acid vary from person to person. The issues below are only potential reactions and are unlikely for most users when the ingredient is used at typical cleanser levels.
Transient stinging on broken or severely irritated skin
Mild redness or tightness in individuals with extremely sensitive skin
Eye irritation if the product is accidentally rubbed into the eyes before rinsing
Contact dermatitis in the rare case of true surfactant allergy
If any discomfort or prolonged irritation occurs discontinue use and consult a medical professional.
Comedogenic Rating
Rating: 0–1 (very low)
C9-11 Alketh-8 Carboxylic Acid is highly water soluble and is almost always used in rinse-off products, so it spends very little time on the skin and does not leave behind an oily film that could block pores. Its molecular structure lacks long hydrophobic tails that typically contribute to clogging. For these reasons formulators regard it as virtually non-comedogenic.
Suitable for acne-prone or breakout-prone skin.
Because most cleansers contain several surfactants and conditioning agents, pore-clogging potential depends on the full formula rather than this ingredient alone.
Summary
C9-11 Alketh-8 Carboxylic Acid is a mild nonionic surfactant that excels at lifting oil, makeup and everyday dirt so they rinse away cleanly. Its balanced water-loving and oil-loving segments create micelles that capture grime while staying gentle on the skin barrier.
Although not as famous as sulfates or newer plant based surfactants, it appears in a respectable number of facial cleansers, body washes and micellar waters where formulators want effective yet soft cleansing.
Current data show it to be low risk for irritation sensitization and pore clogging when used at typical levels. Still every skin is unique so it is wise to patch test any new product that contains this surfactant before fully incorporating it into a routine.