What Is C11-21 Alketh-10?
C11-21 Alketh-10 is a nonionic ingredient made by attaching about ten units of ethylene oxide to a mix of synthetic fatty alcohols that range from 11 to 21 carbon atoms. The raw fatty alcohols can come from either refined petroleum fractions or plant oils such as coconut or palm, depending on the supplier. First introduced in the 1970s as part of a move toward gentler surfactants, it was originally known as C11-21 Pareth-10 before the naming rules for cosmetic ingredients changed. Production begins with purification of the fatty alcohol blend, followed by a controlled ethoxylation step where ethylene oxide gas reacts with the alcohols at high pressure to form the polyethylene glycol ether. The result is a waxy or pasty material that dissolves easily in both water and oil, making it ideal for use in lotions, creams, serums, masks, cleansers and leave-on hair treatments.
C11-21 Alketh-10’s Cosmetic Benefits/Uses
This ingredient plays one essential role in formulas.
As an emulsifier it helps oil and water stay mixed so the product looks smooth, feels light and delivers its active ingredients evenly with every use. A stable emulsion also improves shelf life which means the texture and performance of the lotion, cream or cleanser remain consistent from the first application to the last.
Who Can Use C11-21 Alketh-10
C11-21 Alketh-10 is considered gentle enough for normal, dry, oily and combination skin. Because it is nonionic and used at low levels it is also generally well tolerated by sensitive skin, though those with a known allergy to polyethylene glycols or fatty alcohols should proceed carefully.
The ingredient is synthetic or plant derived and does not come from animals, so it is normally suitable for vegans and vegetarians. If plant sourcing is important, check that the brand specifies coconut or palm origins rather than petroleum.
No data indicate that topical use poses a special risk to women who are pregnant or breastfeeding. Still, this is not medical advice and anyone who is pregnant or nursing should review any skincare product with a qualified doctor to be sure it fits their personal needs.
C11-21 Alketh-10 does not make skin more sensitive to sunlight and can be used in both day and night formulas. It is compatible with most common cosmetic actives and does not interfere with sunscreen filters or color cosmetics.
Potential Side Effects/Adverse Reactions
Side effects from topical C11-21 Alketh-10 can vary from person to person. The following list shows potential reactions but they are uncommon when the ingredient is used correctly in a finished product.
- Mild stinging or burning on highly sensitive skin
- Temporary redness or itching
- Contact dermatitis in individuals allergic to polyethylene glycols or fatty alcohols
- Eye irritation if the formula accidentally gets into the eyes
- Rare clogged pores or breakouts in acne-prone skin when used in heavy leave-on products
If any of these effects occur stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 1/5. C11-21 Alketh-10 is largely water soluble thanks to its ten ethylene oxide units, so it rinses off skin easily and is used at low percentages. While the underlying fatty alcohols could in theory clog pores, the ethoxylation process reduces that risk, earning the ingredient a very low comedogenic score. Most people prone to acne or breakouts can use products containing C11-21 Alketh-10 without issues. The only caveat is in very rich leave-on formulas where multiple heavy oils are present; in that context the whole blend, not this single emulsifier, could potentially feel greasy.
Summary
C11-21 Alketh-10 is a nonionic emulsifier that keeps the water and oil parts of creams, lotions, cleansers and hair products blended into a smooth stable mixture. By lowering surface tension it disperses droplets evenly so the product feels light, spreads well and delivers actives uniformly. It is a workhorse ingredient but not a headline grabber, so it appears more quietly on ingredient lists compared with better-known emulsifiers like polysorbates or PEG-100 stearate.
Overall safety data are strong. The molecule does not sensitize skin, does not increase sun sensitivity and has a very low risk of clogging pores or triggering irritation when used as intended. Still, everyone’s skin is different and formulations vary, so patch testing any new product that contains C11-21 Alketh-10 is a smart step before full-face or full-body use.