Ingredient review
Isosteareth-11 Carboxylic Acid
INCI: ISOSTEARETH-11 CARBOXYLIC ACID
A gentle, semi-synthetic surfactant that effectively cleanses without stripping the skin, making it a good choice for sensitive or dry skin types.
In plain English
Isosteareth-11 Carboxylic Acid is a mild cleansing ingredient that helps water mix with oil and dirt so they can be rinsed away. It is made from a fatty alcohol (isostearyl alcohol) and ethylene oxide, then modified with a carboxylic acid group to make it even gentler. Unlike harsher soaps, it cleans without leaving skin feeling tight or dry, and it also helps other ingredients blend together in a formula.
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
Isosteareth-11 Carboxylic Acid 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 Isosteareth-11 Carboxylic Acid.
- 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 and emulsifier belonging to the ether carboxylic acid family. It is produced by reacting isostearyl alcohol with ethylene oxide (ethoxylation) and then introducing a carboxylic acid group. This structure gives it both water-loving and oil-loving properties, allowing it to lift away sebum, makeup, and environmental debris.
How it works
In a cosmetic product, Isosteareth-11 Carboxylic Acid reduces the surface tension between water and oil, enabling them to mix. Its oil-loving tail attaches to dirt and oil on the skin, while its water-loving head allows the mixture to be rinsed away with water. The carboxylic acid group also gives it a slightly acidic pH, which helps maintain the skin's natural acid mantle and reduces irritation potential.
Pros
Very gentle cleansing
Cleans effectively without disrupting the skin barrier, making it ideal for daily use on sensitive or dry skin.
pH-friendly
Its carboxylic acid group helps maintain a slightly acidic pH, supporting the skin's natural protective acid mantle.
Cons and cautions
Ethoxylation concerns
As an ethoxylated ingredient, it may contain trace amounts of 1,4-dioxane, a potential carcinogen, though reputable manufacturers purify to safe levels.
Not natural
It is semi-synthetic and not suitable for consumers seeking exclusively natural or organic formulations.
Best for
- People with dry or sensitive skin looking for a gentle cleanser
- Anyone who prefers mild, non-stripping cleansing products
Use caution if
- Those seeking 100% natural or organic-only ingredient lists
- Individuals with known allergies to ethoxylated compounds (rare)
Usage tips
Safety summary
Isosteareth-11 Carboxylic Acid is considered safe for use in cosmetics at typical concentrations. The main safety consideration is the potential presence of 1,4-dioxane from ethoxylation, but reputable manufacturers use purification methods to keep levels well below safety limits. It has low irritation and comedogenic potential, making it suitable for most skin types.
Research notes
Research on ether carboxylic acids indicates they are mild surfactants with good skin compatibility. While specific studies on Isosteareth-11 Carboxylic Acid are limited, the broader class of alkyl ether carboxylates is well-documented for low irritation and effective cleansing. The Cosmetic Ingredient Review has reviewed similar ingredients and found them safe with proper manufacturing controls.
Common label clues
- Typical concentration
- 1–10% in rinse-off products; lower in leave-on formulations
- Regulatory status
- Approved for use in cosmetics in the EU, US, and many other regions. The Cosmetic Ingredient Review (CIR) panel has evaluated similar ethoxylated surfactants and found them safe when formulated to minimize 1,4-dioxane.
- Common uses
- Cleansers, Facial washes, Shampoos, Body washes, Makeup removers
- Environmental note
- Biodegradable under standard conditions, but the ethoxylation process has a moderate environmental footprint. Purification steps can reduce potential contaminants.
Good to know
- Isosteareth-11 Carboxylic Acid is often used in 'soap-free' cleansers marketed for sensitive skin.
- It is considered biodegradable and generally safe for aquatic environments at typical use levels.
Common questions
What is Isosteareth-11 Carboxylic Acid in beauty products?
Isosteareth-11 Carboxylic Acid is a mild cleansing ingredient that helps water mix with oil and dirt so they can be rinsed away. It is made from a fatty alcohol (isostearyl alcohol) and ethylene oxide, then modified with a carboxylic acid group to make it even gentler. Unlike harsher soaps, it cleans without leaving skin feeling tight or dry, and it also helps other ingredients blend together in a formula.
What does Isosteareth-11 Carboxylic Acid do in a beauty product?
In a cosmetic product, Isosteareth-11 Carboxylic Acid reduces the surface tension between water and oil, enabling them to mix. Its oil-loving tail attaches to dirt and oil on the skin, while its water-loving head allows the mixture to be rinsed away with water. The carboxylic acid group also gives it a slightly acidic pH, which helps maintain the skin's natural acid mantle and reduces irritation potential.
Is Isosteareth-11 Carboxylic Acid safe for most people?
Isosteareth-11 Carboxylic Acid is considered safe for use in cosmetics at typical concentrations. The main safety consideration is the potential presence of 1,4-dioxane from ethoxylation, but reputable manufacturers use purification methods to keep levels well below safety limits. It has low irritation and comedogenic potential, making it suitable for most skin types.
Who should be careful with Isosteareth-11 Carboxylic Acid?
Those seeking 100% natural or organic-only ingredient lists Individuals with known allergies to ethoxylated compounds (rare)
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.