Ingredient review
Potassium Undecylenoyl Hydrolyzed Soy Protein
INCI: POTASSIUM UNDECYLENOYL HYDROLYZED SOY PROTEIN
A mild, amino-acid-based surfactant that cleanses without stripping, making it a great choice for sensitive or dry skin.
In plain English
This ingredient is a gentle cleanser made by combining soy protein with a fatty acid from castor oil. It works like a mild soap that removes dirt and oil without leaving your skin feeling tight or dry. Because it's derived from natural sources and is very gentle, it's often used in products for sensitive skin or baby care.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- semi synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Potassium Undecylenoyl Hydrolyzed Soy Protein is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Potassium Undecylenoyl Hydrolyzed Soy Protein.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A semi-synthetic surfactant created by reacting undecylenic acid (from castor oil) with hydrolyzed soy protein, then neutralizing with potassium hydroxide. It belongs to the class of amino-acid-based surfactants known for their mildness.
How it works
It reduces the surface tension of water, allowing oil and dirt to be lifted away from the skin. Unlike harsher detergents, it has a larger molecular structure that is less penetrating, so it cleans without disrupting the skin's natural moisture barrier.
Pros
Extremely gentle on skin
Its large molecular structure means it cleans without penetrating or irritating the skin barrier, making it ideal for daily use on sensitive or compromised skin.
Helps maintain moisture
Unlike harsh detergents that strip natural oils, this ingredient leaves skin feeling soft and hydrated after cleansing.
Cons and cautions
Lower foam production
It produces a creamy, low-lather foam that some users may find less satisfying compared to sulfate-based cleansers.
Limited heavy-duty cleansing
It may struggle to remove heavy makeup or waterproof sunscreen on its own, often requiring a double-cleansing step.
Best for
- People with dry, sensitive, or eczema-prone skin
- Those looking for a sulfate-free cleanser
Use caution if
- Anyone with a known soy allergy should patch test first
Usage tips
Safety summary
Potassium Undecylenoyl Hydrolyzed Soy Protein is considered safe for use in cosmetics. It has low irritation and comedogenic potential, and is well-tolerated even by sensitive skin. As with any soy-derived ingredient, individuals with soy allergies should patch test.
Research notes
Amino-acid-based surfactants like this one are well-documented in cosmetic science for their mildness and skin compatibility. While specific studies on this exact ingredient are limited, the broader class is supported by dermatological research showing reduced irritation compared to traditional sulfates.
Common label clues
- Typical concentration
- 1–10% in rinse-off products
- Regulatory status
- Approved for use in cosmetics in the EU, US, and other major markets. No known restrictions at typical use levels.
- Common uses
- Facial cleansers, Body washes, Shampoos, Baby care
- Environmental note
- Derived from renewable castor oil and soy protein, and is biodegradable, making it a more sustainable choice compared to petroleum-based surfactants.
Good to know
- This ingredient is often listed near the middle or end of an ingredient list, as it is used at moderate concentrations.
- It is considered biodegradable and more environmentally friendly than many traditional surfactants.
Common questions
What is Potassium Undecylenoyl Hydrolyzed Soy Protein in beauty products?
This ingredient is a gentle cleanser made by combining soy protein with a fatty acid from castor oil. It works like a mild soap that removes dirt and oil without leaving your skin feeling tight or dry. Because it's derived from natural sources and is very gentle, it's often used in products for sensitive skin or baby care.
What does Potassium Undecylenoyl Hydrolyzed Soy Protein do in a beauty product?
It reduces the surface tension of water, allowing oil and dirt to be lifted away from the skin. Unlike harsher detergents, it has a larger molecular structure that is less penetrating, so it cleans without disrupting the skin's natural moisture barrier.
Is Potassium Undecylenoyl Hydrolyzed Soy Protein safe for most people?
Potassium Undecylenoyl Hydrolyzed Soy Protein is considered safe for use in cosmetics. It has low irritation and comedogenic potential, and is well-tolerated even by sensitive skin. As with any soy-derived ingredient, individuals with soy allergies should patch test.
Who should be careful with Potassium Undecylenoyl Hydrolyzed Soy Protein?
Anyone with a known soy allergy should patch test first
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.