What Is C9-11 Pareth-2?
C9-11 Pareth-2 is a man-made ingredient created by attaching two units of ethylene oxide to a blend of fatty alcohols that contain nine to eleven carbon atoms. This process turns the fatty alcohols into a mild surfactant, meaning it can mix oil and water. The fatty alcohols themselves are usually derived from petroleum or plant oils, then reacted with ethylene oxide in a controlled, high-pressure setting. The result is a clear to slightly hazy liquid that dissolves in water and helps lift away dirt and oil.
The use of such ethoxylated alcohols in cosmetics started in the mid-20th century when chemists searched for gentler cleaning agents than traditional soaps. Over time, C9-11 Pareth-2 earned a spot in personal care products because it offers reliable cleansing without a strong scent or heavy feel.
Today you can spot C9-11 Pareth-2 in face washes, micellar waters, body washes, shampoos, makeup removers, exfoliating scrubs and even sheet masks. Formulators like it because a small amount boosts foam, improves rinse-off and keeps formulas stable.
C9-11 Pareth-2’s Cosmetic Benefits/Uses
C9-11 Pareth-2 serves one main purpose in skincare and haircare formulas: cleansing. By lowering the surface tension between oil and water, it helps disperse grime, makeup and excess sebum so they can be washed away. This makes products feel fresh, rinse clean and leave skin or hair free of residue, all without the tightness some stronger surfactants can cause.
Who Can Use C9-11 Pareth-2
Most skin types, including oily, combination, normal and even many sensitive skins, can generally tolerate C9-11 Pareth-2 because it is considered a mild cleansing agent. Extremely sensitive or compromised skin may find any surfactant drying, so those users should pay attention to how their skin feels after use.
The ingredient itself is synthetic and not made from animal by-products, so products that list C9-11 Pareth-2 are usually suitable for vegans and vegetarians. Always check the full formula though, since other ingredients in the same product might come from animal sources.
There is no evidence that topical use of C9-11 Pareth-2 poses a specific risk during pregnancy or while breastfeeding. This is not medical advice, and anyone who is pregnant or nursing should ask their doctor before adding new skincare products, just to be on the safe side.
C9-11 Pareth-2 does not make skin more sensitive to sunlight, so there is no added need for sun-specific precautions beyond the normal daily use of sunscreen.
Potential Side Effects/Adverse Reactions
Reactions to C9-11 Pareth-2 differ from person to person. The points below cover potential side effects but they are uncommon when the ingredient is used correctly in finished products.
- Temporary skin dryness or tightness if the formula is left on the skin too long or used too often
- Mild redness or irritation, most often in people with very sensitive skin
- Eye stinging and watering if the product accidentally gets into the eyes
- Rare allergic contact dermatitis marked by itching, swelling or rash
If you experience any of these issues stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 0/5. C9-11 Pareth-2 is a lightweight water-soluble surfactant that rinses away completely, so it does not leave a film that could clog pores. It also lacks the heavy oils or waxes typically linked to breakouts.
That makes it a suitable choice for acne-prone or easily congested skin.
Because it is mostly used in rinse-off formulas, the few seconds it stays on the skin further lowers any pore-clogging risk.
Summary
C9-11 Pareth-2 is a mild cleansing agent that lowers surface tension so water can mix with oil, lifting away dirt makeup and excess sebum for an easy rinse-off. It shows up in face cleansers, shampoos, body washes and micellar waters because a small amount boosts foam and improves formula stability without adding scent or weight.
While not as famous as some newer plant-based surfactants, it remains a reliable workhorse in many everyday products thanks to its balance of gentleness and effectiveness.
Current safety data classifies C9-11 Pareth-2 as low risk for irritation or sensitization when used at typical levels. Still, everyone’s skin is unique so it is smart to patch test any new product that contains this ingredient.