What Is Octoxynol-9 Carboxylic Acid?
Octoxynol-9 Carboxylic Acid is a synthetic ingredient that belongs to the large family of nonionic surfactants. Chemically it is 26-(Octylphenoxy)-3,6,9,12,15,18,21,24-octaoxahexacosanoic acid, a long chain molecule built around an octylphenol group linked to multiple ethoxy units and ending in a carboxylic acid. Most manufacturers start with octylphenol derived from petrochemical feedstocks or, less often, plant-based hydrocarbons. Through a process called ethoxylation, ethylene oxide is added stepwise to create the repeating “oxa” segments, after which the terminal end is converted to a carboxylic acid in a controlled oxidation step.
Nonionic surfactants like this one gained popularity in cosmetics during the 1960s when formulators looked for milder alternatives to traditional soaps. Octoxynol-9 Carboxylic Acid soon found a place in personal care because its acid group improves water solubility and keeps the ingredient stable across a wide pH range. Today it appears in facial cleansers, micellar waters, makeup removers, body washes, shampoos, exfoliating masks and some anti-pollution skincare lines where gentle yet effective cleansing is needed.
Octoxynol-9 Carboxylic Acid’s Cosmetic Benefits/Uses
In topical products Octoxynol-9 Carboxylic Acid serves one primary purpose that drives its inclusion in formulas:
Cleansing: The molecule’s surfactant structure helps loosen and lift oil, dirt and leftover makeup from the skin or hair while forming a stable emulsion that can be rinsed away with water. Because it is nonionic it tends to be less irritating than many sulfate-based cleansers, allowing formulators to create products that clean effectively without leaving the skin feeling tight or stripped of its natural moisture.
Who Can Use Octoxynol-9 Carboxylic Acid
This surfactant is considered gentle enough for most skin types including oily, dry, normal and combination because its nonionic nature cleans without stripping the skin’s protective lipids. People with very sensitive or compromised skin may still experience slight irritation if the formula contains a high percentage, so choosing products from reputable brands is important.
Octoxynol-9 Carboxylic Acid is produced synthetically from petrochemical or plant-derived raw materials with no animal by-products, making it suitable for vegans and vegetarians. Always check the full ingredient list to be sure the finished product is free of animal-derived additives.
Current cosmetic use levels are considered low risk for pregnant or breastfeeding women, yet research on this specific ingredient during pregnancy is limited. This information is not medical advice and anyone who is pregnant or nursing should review any skincare product with their doctor to stay on the safe side.
The molecule is not known to cause photosensitivity, so it does not make skin more reactive to sunlight. It also plays well with most other common skincare actives because it is chemically stable across a broad pH range.
Potential Side Effects/Adverse Reactions
Reactions to topical Octoxynol-9 Carboxylic Acid differ from person to person. The points below outline potential side effects yet these outcomes are uncommon when the ingredient is used correctly in a well-formulated product.
- Mild skin irritation
- Redness or a stinging sensation on very sensitive skin
- Dryness if used in a high-foaming or strongly cleansing formula
- Contact dermatitis in individuals with a specific allergy to phenoxyethoxylates
- Eye irritation if the product accidentally gets into the eyes
If any of these effects occur stop using the product and consult a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1/5
Octoxynol-9 Carboxylic Acid is a highly water-soluble surfactant that is usually present in rinse-off products at low levels. It does not leave an oily or waxy residue behind which greatly lowers the chance of clogging pores, but because it is derived from an octylphenol backbone it is given a conservative rating of 1 rather than 0.
Suitable for acne-prone or breakout-prone skin.
Since most formulas containing this ingredient are cleansers that are rinsed away, real-world pore-clogging risk is even lower than the rating suggests.
Summary
Octoxynol-9 Carboxylic Acid is a synthetic nonionic surfactant whose main job is cleansing. Its long chain with multiple ethoxy units grabs onto oil and dirt while its carboxylic acid end keeps the whole molecule water friendly, allowing grime to be lifted and rinsed away without stripping the skin.
It is not a marquee skincare star yet it remains a quiet workhorse in facial washes, micellar waters and gentle shampoos where formulators want mild cleansing performance.
Overall safety data show it is well tolerated by most skin types with only a small risk of irritation at higher concentrations. As with any new cosmetic ingredient it is smart to patch test a new product first to confirm personal compatibility.