What Is C11-15 Pareth-5?
C11-15 Pareth-5 is a nonionic surfactant made by reacting medium-chain synthetic fatty alcohols that have 11 to 15 carbon atoms with about five units of ethylene oxide. This reaction, called ethoxylation, links the oily alcohol side with water-loving ethoxy groups, giving the ingredient the power to mix oil and water. Nonionic surfactants like C11-15 Pareth-5 gained popularity in the 1950s when formulators looked for milder cleansing agents that worked in a wide pH range and were less likely to irritate skin.
The process starts with petro- or plant-derived fatty alcohols. These are purified, then fed into a reactor with ethylene oxide gas under heat and pressure. After five molar units of ethylene oxide bond to each alcohol molecule, the product is cooled, neutralized and filtered, resulting in a clear to slightly hazy liquid.
Because it lifts dirt while helping oil and water stay blended, C11-15 Pareth-5 appears in many wash-off and leave-on items. You will see it in facial cleansers, body washes, micellar waters, shampoos, makeup removers, exfoliating masks, lightweight lotions, sunscreens and even some anti-aging serums where a low-foam cleanser or stable emulsion is needed.
C11-15 Pareth-5’s Cosmetic Benefits/Uses
In formulas, C11-15 Pareth-5 serves two main roles that improve both performance and texture.
- Cleansing: Its surfactant nature breaks the surface tension between oil and water so excess sebum, makeup and daily grime rinse away easily, leaving skin and hair feeling fresh without a heavy residue
- Emulsifying: It helps blend oil and water phases into a smooth, uniform mixture which keeps creams and lotions from separating during storage and use, giving products a pleasant feel and consistent delivery of active ingredients
Who Can Use C11-15 Pareth-5
C11-15 Pareth-5 is generally well tolerated by most skin types including oily, combination, normal and many sensitive skins because it is a mild nonionic surfactant. People with very dry or compromised skin barriers should check the overall formula since high levels of any cleanser may increase tightness or flaking.
The ingredient is usually produced from synthetic or plant sourced fatty alcohols and ethylene oxide so it is suitable for vegans and vegetarians provided the finished product is certified animal free.
C11-15 Pareth-5 is not known to interfere with pregnancy or lactation when used topically. Still this information is not medical advice and pregnant or nursing women should run any skincare routine past a doctor to be safe.
It does not cause photosensitivity, so daylight exposure while using products containing it is not a concern.
Potential Side Effects/Adverse Reactions
Side effects from topical use of C11-15 Pareth-5 can vary from person to person. The following list covers potential reactions, but most users will not experience them when the ingredient is properly formulated in a product.
- Mild skin irritation such as redness or stinging, especially in high concentration rinse off formulas
- Dryness or tightness if the product is left on the skin too long or used too frequently
- Allergic contact dermatitis in individuals sensitive to ethoxylated surfactants, though this is rare
- Eye irritation if the cleanser accidentally gets into the eyes
If any negative reaction occurs stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 0-1. C11-15 Pareth-5 is a lightweight, water-soluble surfactant that rinses clean without leaving an oily film that could clog pores. Because it does not stay on the skin in significant amounts and has no occlusive properties, its likelihood of triggering comedones is very low. For these reasons it is generally considered safe for acne-prone or breakout-prone skin. In the rare case of a leave-on product formulated with a high percentage, the overall formula should still be assessed, but the ingredient itself poses minimal pore-clogging risk.
Summary
C11-15 Pareth-5 acts as a mild cleanser and an effective emulsifier. Its structure links an oil-loving fatty alcohol chain with roughly five ethoxy units that love water, allowing it to lift dirt while keeping oil and water phases blended in stable, smooth products. This dual action makes it a handy workhorse in face washes, micellar waters, light lotions and similar everyday items.
It is a fairly common ingredient because formulators appreciate its versatility, skin friendliness and ability to work in a broad pH range, though it does not have the household name status of sulfates or classic emulsifiers.
Overall safety is high: published data and market use show a low irritation profile, no known systemic issues and virtually no comedogenicity. As with any new skincare product, a patch test is wise to ensure personal compatibility.