What Is C11-21 Alketh-3?
C11-21 Alketh-3 is a man-made ingredient created by attaching about three units of ethylene oxide to a blend of synthetic fatty alcohols that range from 11 to 21 carbon atoms in length. The result is a mild, water-compatible substance that helps oil and water stay mixed. The process, called ethoxylation, begins with plant- or petroleum-derived fatty alcohols that are purified, then reacted with ethylene oxide gas under controlled heat and pressure. Chemists started exploring this type of chemistry in the mid-20th century when the beauty industry looked for alternatives to soap that would be gentler on skin and work in a wider range of formulas. Over time C11-21 Alketh-3 earned a place in many everyday products because it is effective in small amounts, has a low scent and fits well with a broad pH range.
You are most likely to encounter this ingredient in moisturizers, lotions, face and body creams, cleansing milks, liquid foundations, sunscreens, hair conditioners and rinse-off masks. Its ability to keep the formula uniform means the product feels the same from the first pump to the last squeeze.
C11-21 Alketh-3’s Cosmetic Benefits/Uses
C11-21 Alketh-3 has one main job in cosmetics: it works as an emulsifier. By sitting at the boundary between oil and water, it keeps these two parts from separating, which gives a product a smooth, stable texture. A reliable emulsifier prevents the watery phase from leaking or the oily phase from pooling on top, so the cream or lotion you apply glides on evenly, feels lighter and delivers its active ingredients more consistently over time.
Who Can Use C11-21 Alketh-3
Because C11-21 Alketh-3 is mild and primarily serves as an emulsifier it tends to be well tolerated by most skin types, including oily, dry, combination and even many sensitive skins. Those with severely compromised or broken skin, such as active eczema or open wounds, may prefer to avoid products with any surfactant-like ingredient until the area has healed.
The ingredient is typically produced from plant or petroleum sources with no animal-derived inputs, so it is generally suitable for vegans and vegetarians. That said manufacturing practices can vary, so ethical consumers may want to confirm a finished product’s full supply chain with the brand.
C11-21 Alketh-3 has no known issues specific to pregnancy or breastfeeding when used in cosmetic amounts. It is not absorbed deeply into the skin and does not interfere with hormones. Still this is not medical advice; anyone who is pregnant or nursing should review any skincare routine with a qualified healthcare provider to be safe.
The molecule does not make skin more sensitive to sunlight and carries no risk of photosensitivity. It is also fragrance-free, low odor and compatible with most other common cosmetic ingredients.
Potential Side Effects/Adverse Reactions
Side effects and reactions to topical C11-21 Alketh-3 can vary from person to person. The list below covers potential issues, but they are uncommon when the ingredient is used correctly and at standard cosmetic levels.
- Mild irritation such as transient stinging or burning, especially on very sensitive skin
- Redness, itching or swelling in cases of allergic contact dermatitis
- Dry or tight feeling if the formula contains a high percentage of the ingredient or other surfactants
- Watery eyes if the product accidentally gets into the eye area, as the ingredient can act as a mild detergent
If you notice any of the above reactions stop using the product and seek advice from a pharmacist or healthcare professional.
Comedogenic Rating
Rating: 1 out of 5. C11-21 Alketh-3 is mainly water compatible and used at low levels so it does not leave an oily film that could block pores. It rinses away cleanly and is chemically too large to slip into follicles where clogs start. For these reasons it sits at the low end of the scale.
Most people who are prone to acne or breakouts can use products containing C11-21 Alketh-3 without added risk.
Because formulas differ, a heavy cream loaded with rich oils could still feel greasy even if it includes this low-risk emulsifier, so consider the whole ingredient list rather than any single component.
Summary
C11-21 Alketh-3 acts as an emulsifier, keeping oil and water mixed so lotions, creams and makeup stay smooth and stable. It does this by having a water-loving side and an oil-loving side, allowing it to sit at the boundary of both phases and lock them together.
The ingredient is not a household name like glycerin or hyaluronic acid, yet it shows up quietly in many everyday formulas because it works well, has little scent and plays nicely with other ingredients.
Safety profiles and decades of use point to low irritation potential and almost no long-term concerns. Still, everyone’s skin is different so it is wise to patch test any new product that contains C11-21 Alketh-3 before using it on larger areas.