Ingredient review
Steareth-40
INCI: STEARETH-40
Steareth-40 is a gentle synthetic emulsifier that helps mix water and oil in creams and lotions, with a low risk of irritation or clogged pores.
In plain English
Steareth-40 is a man-made ingredient that acts like a bridge between water and oil. In a moisturizer or cleanser, it keeps the formula from separating into layers, so you get a smooth, consistent product every time you use it. It belongs to a family of ingredients called ethoxylated alcohols, which are widely used in cosmetics because they are mild and effective.
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
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Steareth-40 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 Steareth-40.
- 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
Steareth-40 is a polyethylene glycol (PEG) derivative of stearyl alcohol, a fatty alcohol from plant or synthetic sources. The number 40 indicates the average length of the PEG chain, which makes it water-loving and helps it function as an emulsifier.
How it works
Steareth-40 has both water-loving and oil-loving parts. When added to a formula, it positions itself at the boundary between water droplets and oil droplets, reducing surface tension so they can mix into a stable emulsion. This prevents the product from separating and gives it a smooth, uniform texture.
Pros
Gentle on skin
Steareth-40 has a low irritation risk and is well-tolerated even by sensitive skin types, making it a common choice in daily moisturizers and cleansers.
Effective emulsifier
It reliably blends water and oil into a stable, creamy texture, so your product stays consistent from first use to last without separating.
Cons and cautions
Potential for trace contaminants
As an ethoxylated ingredient, Steareth-40 may contain trace amounts of 1,4-dioxane, a byproduct that some consumers prefer to avoid. Reputable manufacturers purify to reduce this.
Environmental persistence
PEG-based compounds like Steareth-40 can be slow to biodegrade, which raises concerns for some eco-conscious users.
Best for
- Anyone looking for a gentle, non-irritating emulsifier in their skincare
- People with normal to dry skin who use cream-based moisturizers
Use caution if
- Those who prefer to avoid PEG-derived ingredients due to personal or environmental concerns
Usage tips
Safety summary
Steareth-40 is considered safe for use in cosmetics at typical concentrations. The main concern is the potential presence of 1,4-dioxane, but reputable manufacturers use purification steps to keep levels very low. Regulatory bodies like the Cosmetic Ingredient Review (CIR) have reviewed similar ethoxylated alcohols and found them safe as used.
Research notes
Studies on ethoxylated alcohols like Steareth-40 indicate low acute toxicity and skin irritation. The CIR Expert Panel has reviewed related ingredients and concluded they are safe in current usage patterns. Research on 1,4-dioxane contamination focuses on manufacturing controls rather than the ingredient itself.
Common label clues
- Typical concentration
- Usually 0.5% to 5% of the formula
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions. The EU CosIng database lists it as a safe emulsifier. Manufacturers are encouraged to follow good manufacturing practices to minimize 1,4-dioxane.
- Common uses
- Moisturizers, Cleansers, Sunscreens, Hair conditioners
- Environmental note
- Steareth-40 is synthetic and may not biodegrade quickly. Some consumers prefer plant-based or biodegradable alternatives for environmental reasons.
Good to know
- Steareth-40 is often used alongside other emulsifiers to fine-tune texture and stability.
- The '40' in its name refers to the number of ethylene oxide units, which affects how water-soluble it is.
Common questions
What is Steareth-40 in beauty products?
Steareth-40 is a man-made ingredient that acts like a bridge between water and oil. In a moisturizer or cleanser, it keeps the formula from separating into layers, so you get a smooth, consistent product every time you use it. It belongs to a family of ingredients called ethoxylated alcohols, which are widely used in cosmetics because they are mild and effective.
What does Steareth-40 do in a beauty product?
Steareth-40 has both water-loving and oil-loving parts. When added to a formula, it positions itself at the boundary between water droplets and oil droplets, reducing surface tension so they can mix into a stable emulsion. This prevents the product from separating and gives it a smooth, uniform texture.
Is Steareth-40 safe for most people?
Steareth-40 is considered safe for use in cosmetics at typical concentrations. The main concern is the potential presence of 1,4-dioxane, but reputable manufacturers use purification steps to keep levels very low. Regulatory bodies like the Cosmetic Ingredient Review (CIR) have reviewed similar ethoxylated alcohols and found them safe as used.
Who should be careful with Steareth-40?
Those who prefer to avoid PEG-derived ingredients due to personal or environmental concerns
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.