Ingredient review
PEG-400
INCI: PEG-400
PEG-400 is a widely used synthetic ingredient that helps dissolve other ingredients and improve texture, but its safety depends on purity and molecular weight.
In plain English
PEG-400 is a type of polyethylene glycol, a synthetic compound made from ethylene oxide and water. It is a clear, viscous liquid that acts as a solvent (helps other ingredients dissolve), a humectant (attracts moisture), and a skin-conditioning agent. In skincare, it helps create smooth, spreadable formulas and can improve the feel of products on the skin. PEG-400 is generally considered safe at low concentrations, but concerns exist about potential impurities from its manufacturing process.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is relatively strong for its common cosmetic role.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- strong
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
PEG-400 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 PEG-400.
- 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
strongThere is a stronger practical or research basis for the ingredient role described here.
What it is
PEG-400 is a low-molecular-weight polyethylene glycol (PEG) with an average molecular weight of 400. It is a clear, colorless, viscous liquid that is water-soluble and used as a solvent, humectant, and skin-conditioning agent in cosmetics.
How it works
PEG-400 works by dissolving other ingredients that are not easily mixed with water, helping to create stable, uniform formulas. It also attracts and holds moisture on the skin's surface, providing a temporary hydrating effect. Its low molecular weight allows it to penetrate the skin slightly, which can enhance the delivery of other active ingredients.
Pros
Improves product feel
PEG-400 helps create smooth, spreadable formulas that feel lightweight on the skin, making it a common choice for serums and cleansers.
Versatile solvent
It can dissolve a wide range of ingredients, including oils and fragrances, helping to create stable, uniform products.
Cons and cautions
Potential impurities
During manufacturing, PEG-400 may contain trace amounts of ethylene oxide or 1,4-dioxane, which are considered potential carcinogens. Reputable brands use purification steps to minimize these.
Skin penetration
Because of its low molecular weight, PEG-400 can penetrate the skin slightly, which may increase the absorption of other ingredients, including potential irritants.
Best for
- People looking for lightweight, non-greasy formulas
- Those using products that need to dissolve multiple ingredients
Use caution if
- Individuals with very sensitive or compromised skin barriers
- Those concerned about potential impurities in synthetic ingredients
Usage tips
Safety summary
PEG-400 is considered safe for use in cosmetics at typical concentrations, but concerns exist about potential impurities from its manufacturing process. Reputable brands use purification steps to minimize these risks. The Cosmetic Ingredient Review panel has concluded that PEGs are safe when formulated to avoid contamination.
Research notes
Studies show that PEG-400 is generally non-irritating and non-sensitizing at low concentrations. However, research has identified potential impurities like 1,4-dioxane in some PEG-containing products. The evidence supports its safety when properly purified, but long-term effects of skin penetration are not fully understood.
Common label clues
- Typical concentration
- Typically 1–10% in leave-on products; higher in rinse-off products
- Regulatory status
- Approved for use in cosmetics by the FDA and the European Commission, with concentration limits in some product categories. The Cosmetic Ingredient Review (CIR) panel has deemed PEGs safe when formulated to minimize impurities.
- Common uses
- Cleansers, Serums, Moisturizers, Makeup removers
- Environmental note
- PEG-400 is synthetic and derived from petroleum. It is biodegradable but may persist in the environment in certain conditions. Some brands are moving toward bio-based alternatives.
Good to know
- PEG-400 is often used in combination with other PEGs to achieve specific textures.
- The number '400' refers to the average molecular weight; higher numbers mean thicker consistency and less skin penetration.
Common questions
What is PEG-400 in beauty products?
PEG-400 is a type of polyethylene glycol, a synthetic compound made from ethylene oxide and water. It is a clear, viscous liquid that acts as a solvent (helps other ingredients dissolve), a humectant (attracts moisture), and a skin-conditioning agent. In skincare, it helps create smooth, spreadable formulas and can improve the feel of products on the skin. PEG-400 is generally considered safe at low concentrations, but concerns exist about potential impurities from its manufacturing process.
What does PEG-400 do in a beauty product?
PEG-400 works by dissolving other ingredients that are not easily mixed with water, helping to create stable, uniform formulas. It also attracts and holds moisture on the skin's surface, providing a temporary hydrating effect. Its low molecular weight allows it to penetrate the skin slightly, which can enhance the delivery of other active ingredients.
Is PEG-400 safe for most people?
PEG-400 is considered safe for use in cosmetics at typical concentrations, but concerns exist about potential impurities from its manufacturing process. Reputable brands use purification steps to minimize these risks. The Cosmetic Ingredient Review panel has concluded that PEGs are safe when formulated to avoid contamination.
Who should be careful with PEG-400?
Individuals with very sensitive or compromised skin barriers Those concerned about potential impurities in synthetic 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.