What Is Sodium Undecylenoamphoacetate?
Sodium Undecylenoamphoacetate is a gentle surfactant derived from undecylenic acid, which itself comes from castor oil. Chemically it is the sodium salt of 10-undecenamide that has been modified with hydroxyethyl and carboxymethyl groups to make it water soluble and skin friendly. This tweak turns the oily undecylenic backbone into a molecule that loves both water and oil, allowing it to lift dirt and oil from skin and hair.
The ingredient first appeared in personal care labs in the late 1970s when formulators were searching for milder alternatives to the harsher sulfates common at the time. By combining a fatty acid sourced from plants with a betaine-like side chain, chemists created a cleanser that produced rich foam without stripping the skin. Over time its mild profile made it a favorite for baby washes and sensitive skin products, and its popularity spread to mainstream shampoos and facial cleansers in the 1990s.
Manufacture starts with undecylenic acid which reacts with ammonia to form undecenamide. This amide then undergoes a series of reactions with chloroacetic acid and ethylene oxide, after which the finished amphoacetate is neutralized with sodium hydroxide. The result is a biodegradable surfactant supplied as a clear to pale-yellow liquid.
You will most often see Sodium Undecylenoamphoacetate in sulfate-free shampoos, foaming facial cleansers, body washes, micellar waters, bubble baths, baby cleansers and some shaving foams. It can also show up in 2-in-1 conditioning shampoos thanks to its mild hair conditioning touch.
Sodium Undecylenoamphoacetate’s Cosmetic Benefits/Uses
Formulators choose this multifaceted ingredient for several helpful roles in a product
- Cleansing: As a mild surfactant it grabs onto oil, makeup and daily grime then lifts them away when rinsed, leaving skin and hair feeling fresh but not tight
- Foaming: It builds a dense creamy lather that consumers associate with effective cleansing even in hard water
- Hair Conditioning: The amphoteric nature means it can deposit a light film on hair strands helping improve softness, manageability and static control without weighing hair down
- Foam Boosting: When used alongside other surfactants it raises total foam volume and stability so the formula feels richer and more luxurious
Who Can Use Sodium Undecylenoamphoacetate
This gentle surfactant is generally suitable for all skin types including dry, normal, combination, oily and especially sensitive skin because it cleans without stripping natural oils. Those with severely compromised or broken skin should still proceed carefully as even mild cleansers can sting on open areas.
The ingredient is plant derived from castor oil and all subsequent processing steps are synthetic, not animal based, so products using it are typically appropriate for vegans and vegetarians. Always check the full label to be sure the finished formula contains no animal sourced additives.
Current safety data indicate no known reproductive or developmental risks from topical use, so pregnant or breastfeeding women can use it in rinse off or leave on products. This is not medical advice and anyone who is pregnant or nursing should run their entire skincare routine past a qualified healthcare provider to be safe.
Sodium Undecylenoamphoacetate does not cause photosensitivity and will not make skin more prone to sunburn. It is also color safe for dyed hair and compatible with most common skincare ingredients.
Potential Side Effects/Adverse Reactions
Responses to any cosmetic ingredient can differ from person to person. The points below list potential side effects that have been reported with topical Sodium Undecylenoamphoacetate yet they remain uncommon when the ingredient is used correctly in a well formulated product.
- Mild skin irritation such as redness or itching in very sensitive individuals
- Transient eye stinging if the product accidentally gets into the eyes before rinsing
- Rare allergic contact dermatitis marked by persistent rash or swelling
If you experience any of these effects stop using the product and seek medical advice if symptoms persist or worsen.
Comedogenic Rating
Rating: 0 / 5
Sodium Undecylenoamphoacetate is a water-soluble surfactant that rinses off completely, leaving no oily film to clog pores. Its molecular structure is large, charged and highly polar which limits its ability to penetrate into follicles where comedones form. In consumer use tests and published safety reviews there are no reports of acne flare-ups linked to this ingredient. Because of this it is considered non-comedogenic and is generally suitable for people who are prone to acne or breakouts.
One extra point worth noting is that products containing rich plant oils or occlusive silicones alongside this surfactant could still contribute to congestion, so pore-clogging risk depends on the full formula, not just one ingredient.
Summary
Sodium Undecylenoamphoacetate works mainly as a mild cleanser, foam builder and light hair conditioner. Its amphoteric structure lets one end bond with oil and the other with water, so it lifts away dirt, makeup and excess sebum while creating a dense creamy lather. A slight positive charge at common cosmetic pH levels helps it smooth the hair cuticle which adds softness and reduces static.
Although not as famous as sulfates or classic coco-based surfactants, this ingredient enjoys steady popularity in sulfate-free shampoos, baby washes and sensitive skin cleansers because it delivers the cleansing feel consumers expect without harshness.
Overall safety data show a very low risk of irritation or allergy, it is biodegradable and suitable for vegans. As with any new skincare or haircare product, patch test first to make sure your skin agrees with the complete formula.