Ingredient review
Ceteareth-40
INCI: Ceteareth-40
Ceteareth-40 is a reliable emulsifier that helps create smooth, stable creams and lotions, but it may be contaminated with 1,4-dioxane in its raw form.
In plain English
Ceteareth-40 is a synthetic ingredient that acts like a bridge between oil and water. In a moisturizer, it stops the oil and water from separating, so you get a smooth, creamy texture every time you use it. It's a type of surfactant, meaning it can also help cleanse the skin by lifting dirt and oil. While it's generally considered safe, some concerns exist because it can be made using a process that leaves behind a trace impurity called 1,4-dioxane, which is a potential carcinogen. However, reputable manufacturers purify the ingredient to remove this impurity, and regulatory bodies set strict limits on its presence in finished products.
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
Ceteareth-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 Ceteareth-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
Ceteareth-40 is a synthetic polymer made by reacting cetearyl alcohol (a fatty alcohol from plant oils) with ethylene oxide. The number 40 indicates the average number of ethylene oxide units in the molecule. It belongs to a class of ingredients called ethoxylated surfactants.
How it works
In a cosmetic formula, Ceteareth-40 reduces the surface tension between oil and water, allowing them to mix into a stable emulsion. It also helps other ingredients spread evenly on the skin and can boost the foaming ability of cleansers.
Pros
Effective emulsifier
Ceteareth-40 reliably blends oil and water, giving creams and lotions a smooth, uniform texture that doesn't separate over time.
Low irritation potential
It is generally well-tolerated by most skin types, including sensitive skin, when used at typical concentrations.
Cons and cautions
Potential 1,4-dioxane contamination
As an ethoxylated ingredient, Ceteareth-40 can be contaminated with 1,4-dioxane, a possible human carcinogen. Reputable brands purify it, but not all do.
Synthetic origin
It is made through a chemical process that uses ethylene oxide, which has environmental and health concerns during manufacturing.
Best for
- Anyone using conventional creams or lotions
- People who prefer stable, well-formulated products
Use caution if
- Those seeking completely ethoxylate-free or 'green' formulations
- Individuals with known sensitivity to ethoxylated ingredients (rare)
Usage tips
Safety summary
Ceteareth-40 is considered safe for use in cosmetics at typical concentrations. The main safety concern is potential contamination with 1,4-dioxane, which is regulated and can be removed through purification. Skin irritation and allergy are rare.
Research notes
The Cosmetic Ingredient Review (CIR) panel has evaluated ethoxylated alcohols and found them safe as used, provided 1,4-dioxane levels are minimized. Studies show low acute toxicity and skin irritation potential.
Common label clues
- Typical concentration
- 1% to 5%
- Regulatory status
- Approved for use in cosmetics by the FDA and the European Commission, with restrictions on 1,4-dioxane levels (typically below 10 ppm in the EU).
- Common uses
- Moisturizers, Cleansers, Sunscreens, Hair conditioners
- Environmental note
- The ethoxylation process uses ethylene oxide, a hazardous chemical. The ingredient itself is not readily biodegradable in all environments, raising concerns about aquatic toxicity.
Good to know
- The number in Ceteareth-XX (e.g., 40) indicates the length of the polyethylene glycol chain, which affects its water solubility and emulsifying strength.
- Ceteareth-40 is considered a microplastic by some definitions, though it is biodegradable under certain conditions.
Common questions
What is Ceteareth-40 in beauty products?
Ceteareth-40 is a synthetic ingredient that acts like a bridge between oil and water. In a moisturizer, it stops the oil and water from separating, so you get a smooth, creamy texture every time you use it. It's a type of surfactant, meaning it can also help cleanse the skin by lifting dirt and oil. While it's generally considered safe, some concerns exist because it can be made using a process that leaves behind a trace impurity called 1,4-dioxane, which is a potential carcinogen. However, reputable manufacturers purify the ingredient to remove this impurity, and regulatory bodies set strict limits on its presence in finished products.
What does Ceteareth-40 do in a beauty product?
In a cosmetic formula, Ceteareth-40 reduces the surface tension between oil and water, allowing them to mix into a stable emulsion. It also helps other ingredients spread evenly on the skin and can boost the foaming ability of cleansers.
Is Ceteareth-40 safe for most people?
Ceteareth-40 is considered safe for use in cosmetics at typical concentrations. The main safety concern is potential contamination with 1,4-dioxane, which is regulated and can be removed through purification. Skin irritation and allergy are rare.
Who should be careful with Ceteareth-40?
Those seeking completely ethoxylate-free or 'green' formulations Individuals with known sensitivity to ethoxylated ingredients (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.