Ingredient review
C20-40 Pareth-24
INCI: C20-40 PARETH-24
A gentle synthetic emulsifier that helps mix oil and water in your products, with a low risk of irritation or clogging pores.
In plain English
C20-40 Pareth-24 is a man-made ingredient that helps oil and water stay mixed together in creams, lotions, and cleansers. Without it, your moisturizer would separate into a watery layer and an oily layer. It belongs to a family of ingredients called alkyl polyethoxylates, which are widely used because they are gentle on skin and effective at low concentrations.
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
C20-40 Pareth-24 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 C20-40 Pareth-24.
- 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 synthetic non-ionic surfactant and emulsifier made from a long-chain fatty alcohol (C20-40) reacted with ethylene oxide. It is part of the 'pareth' family, where the number (24) indicates the average length of the polyethylene glycol chain.
How it works
It reduces the surface tension between oil and water, allowing them to form a stable emulsion. In a cream or lotion, it surrounds tiny oil droplets so they stay suspended in water, preventing separation. It also helps cleanse by lifting dirt and oil from the skin so they can be rinsed away.
Pros
Stable emulsions
It reliably keeps oil and water mixed, so your product stays smooth and effective from first use to last.
Low irritation potential
Compared to many other surfactants, C20-40 Pareth-24 is very gentle on skin and unlikely to cause stinging or redness.
Cons and cautions
Synthetic origin
It is made in a lab from petrochemicals, which may not align with preferences for natural or plant-based ingredients.
Ethoxylation concerns
The manufacturing process can create trace amounts of 1,4-dioxane, a potential contaminant, though reputable brands purify their ingredients to safe levels.
Best for
- Anyone using conventional creams, lotions, or cleansers
- People with normal to sensitive skin looking for a gentle emulsifier
Use caution if
- Those strictly avoiding all synthetic or ethoxylated ingredients
Usage tips
Safety summary
C20-40 Pareth-24 is considered safe for use in cosmetics at typical concentrations. The main safety consideration is the potential for trace 1,4-dioxane contamination, which is tightly regulated. For most users, it poses a very low risk of irritation or allergy.
Research notes
The safety of ethoxylated alcohols like C20-40 Pareth-24 has been reviewed by the Cosmetic Ingredient Review (CIR) panel, which found them safe when formulated to minimize 1,4-dioxane. Individual studies are limited, but the class is well-established in cosmetic chemistry.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics globally, including by the U.S. FDA and EU CosIng database. Manufacturers must ensure low levels of 1,4-dioxane (typically below 10 ppm) to meet safety standards.
- Common uses
- Cleansers, Moisturizers, Sunscreens, Hair products
- Environmental note
- While synthetic, it is biodegradable and does not persist in the environment. However, its production relies on non-renewable petrochemicals.
Good to know
- The 'C20-40' refers to the length of the fatty alcohol chain, which is long and contributes to its mildness.
- It is considered biodegradable under standard wastewater treatment conditions.
Common questions
What is C20-40 Pareth-24 in beauty products?
C20-40 Pareth-24 is a man-made ingredient that helps oil and water stay mixed together in creams, lotions, and cleansers. Without it, your moisturizer would separate into a watery layer and an oily layer. It belongs to a family of ingredients called alkyl polyethoxylates, which are widely used because they are gentle on skin and effective at low concentrations.
What does C20-40 Pareth-24 do in a beauty product?
It reduces the surface tension between oil and water, allowing them to form a stable emulsion. In a cream or lotion, it surrounds tiny oil droplets so they stay suspended in water, preventing separation. It also helps cleanse by lifting dirt and oil from the skin so they can be rinsed away.
Is C20-40 Pareth-24 safe for most people?
C20-40 Pareth-24 is considered safe for use in cosmetics at typical concentrations. The main safety consideration is the potential for trace 1,4-dioxane contamination, which is tightly regulated. For most users, it poses a very low risk of irritation or allergy.
Who should be careful with C20-40 Pareth-24?
Those strictly avoiding all synthetic or ethoxylated ingredients
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.