Ingredient review
Oleth-100
INCI: OLETH-100
Oleth-100 is a gentle synthetic emulsifier that helps blend oil and water in products, but it may be less common in modern formulations due to concerns about ethoxylated ingredients.
In plain English
Oleth-100 is a man-made ingredient that helps oil and water mix together in your skincare products, so they stay smooth and don't separate. It's a type of emulsifier made from oleyl alcohol (a fatty alcohol from plants) and ethylene oxide. While it's effective and generally gentle, some people prefer to avoid ethoxylated ingredients due to potential trace impurities like 1,4-dioxane, though modern manufacturing keeps levels very low.
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
Oleth-100 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 Oleth-100.
- 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
Oleth-100 is a synthetic emulsifier and surfactant derived from oleyl alcohol (a fatty alcohol found naturally in some plant oils) and ethylene oxide. The '100' refers to the average number of ethylene oxide units, making it water-soluble and effective at stabilizing oil-in-water emulsions.
How it works
Oleth-100 works by reducing the surface tension between oil and water, allowing them to blend into a stable, creamy emulsion. In a product, it helps distribute oils evenly in water, improving texture, spreadability, and the delivery of other ingredients to the skin.
Pros
Effective emulsifier
Oleth-100 reliably blends oil and water, giving creams and lotions a smooth, uniform texture that doesn't separate.
Low irritation risk
It is generally well-tolerated on skin, with a low irritation and comedogenic rating, making it suitable for many skin types.
Cons and cautions
Ethoxylation concerns
As an ethoxylated ingredient, Oleth-100 may contain trace amounts of 1,4-dioxane, a potential impurity. Reputable manufacturers purify it to safe levels, but some consumers prefer to avoid it.
Less trendy
Oleth-100 is less common in modern 'clean' beauty formulations, which often favor non-ethoxylated emulsifiers like cetearyl alcohol or glyceryl stearate.
Best for
- People using lotions or creams that need a stable, smooth texture
- Those with normal to dry skin looking for a gentle emulsifier
Use caution if
- Individuals specifically avoiding ethoxylated ingredients due to personal preference or sensitivity concerns
Usage tips
Safety summary
Oleth-100 is considered safe for use in cosmetics at typical concentrations. The main concern is trace 1,4-dioxane, but modern purification methods keep levels well below safety limits. It has low irritation and comedogenic potential.
Research notes
Research on Oleth-100 specifically is limited, but the broader class of ethoxylated alcohols has been reviewed by the Cosmetic Ingredient Review (CIR) and found safe when properly purified. No significant adverse effects have been reported in cosmetic use.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and many other regions. The Cosmetic Ingredient Review (CIR) has evaluated ethoxylated alcohols and found them safe when formulated to minimize 1,4-dioxane.
- Common uses
- Cleansers, Lotions, Creams, Shampoos
- Environmental note
- Oleth-100 is synthetic and may not be readily biodegradable. Its production involves ethylene oxide, which is derived from fossil fuels.
Good to know
- Oleth-100 is part of the Oleth family, where the number indicates the ethylene oxide chain length (higher numbers = more water-soluble).
- It is not typically used in leave-on products at high concentrations due to potential for slight drying with overuse.
Common questions
What is Oleth-100 in beauty products?
Oleth-100 is a man-made ingredient that helps oil and water mix together in your skincare products, so they stay smooth and don't separate. It's a type of emulsifier made from oleyl alcohol (a fatty alcohol from plants) and ethylene oxide. While it's effective and generally gentle, some people prefer to avoid ethoxylated ingredients due to potential trace impurities like 1,4-dioxane, though modern manufacturing keeps levels very low.
What does Oleth-100 do in a beauty product?
Oleth-100 works by reducing the surface tension between oil and water, allowing them to blend into a stable, creamy emulsion. In a product, it helps distribute oils evenly in water, improving texture, spreadability, and the delivery of other ingredients to the skin.
Is Oleth-100 safe for most people?
Oleth-100 is considered safe for use in cosmetics at typical concentrations. The main concern is trace 1,4-dioxane, but modern purification methods keep levels well below safety limits. It has low irritation and comedogenic potential.
Who should be careful with Oleth-100?
Individuals specifically avoiding ethoxylated ingredients due to personal preference or sensitivity 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.