What Is Peg-18?
PEG-18 is a synthetic liquid made by linking about 18 units of ethylene oxide to a starter molecule of ethylene glycol. The result is a small water loving polymer officially named poly(oxy-1,2-ethanediyl) .alpha.-hydro-.omega.-hydroxy- that sits at the middle ground between a fluid and a waxy paste depending on temperature. Because the chain is capped with hydroxyl groups it mixes easily with water and many solvents.
This type of polyethylene glycol has been used by chemists since the mid 1900s for its ability to hold water and dissolve oily or fragrant ingredients. As cosmetic science looked for lighter feeling moisturizers in the 1970s formulators began adding specific chain lengths like PEG-18 to lotions gels and makeup to improve texture without leaving grease.
Industrial production starts with purified ethylene glycol. Under heat pressure and the guidance of a basic catalyst ethylene oxide gas is added step by step until the average chain hits 18 units. The mixture is then neutralized filtered and vacuum stripped to remove any unreacted materials before being quality tested for use on skin.
You will most often spot PEG-18 in lightweight face and body moisturizers, hydrating serums, sheet mask essences, water based foundations, after sun lotions, gentle cleansers and refreshing hair conditioners where it helps bind water and keep formulas clear.
Peg-18’s Cosmetic Benefits/Uses
Here is what PEG-18 brings to the table in your daily beauty products.
- Humectant – pulls moisture from the environment and from deeper skin layers into the upper surface which helps keep skin feeling soft smooth and flexible throughout the day
- Solvent – dissolves active ingredients fragrances and certain lipids allowing formulators to create clear stable products and helping those ingredients spread evenly on the skin
Who Can Use Peg-18
PEG-18 is gentle enough for most skin types including dry, normal, oily and combination since it hydrates without leaving a heavy residue or clogging pores. Highly reactive or compromised skin may still prefer simple formulas with fewer synthetic ingredients but PEG-18 itself is not known for triggering flare-ups.
The ingredient is produced from petroleum-derived raw materials rather than animal sources so it is suitable for both vegans and vegetarians.
Current safety data show no reproductive or developmental risks from topical use and the molecule is too large to penetrate deeply. Pregnant or breastfeeding individuals can generally use products containing PEG-18 but this is not medical advice and anyone in these groups should check with a doctor before starting a new skincare routine to be safe.
PEG-18 does not make skin more sensitive to sunlight and there are no special timing or daylight restrictions when using it. It also plays well with most other cosmetic actives so formulators rarely flag compatibility issues.
Potential Side Effects/Adverse Reactions
Reactions to PEG-18 vary from person to person. The points below list potential but uncommon side effects. When used at standard cosmetic levels most people will not experience these problems.
- Mild redness or stinging in individuals with very sensitive or freshly exfoliated skin
- Contact dermatitis if a person develops an allergy to polyethylene glycols or impurities remaining from manufacturing
- Follicular irritation when high concentrations are applied repeatedly to areas with lots of body hair
- Contamination concerns trace levels of 1,4-dioxane or ethylene oxide can remain if the ingredient is poorly purified which may irritate skin or raise longer term safety questions
- Enhanced penetration of other actives occasionally leading to unintended irritation from stronger ingredients in the same formula
If any uncomfortable reaction occurs discontinue use and seek advice from a qualified healthcare professional.
Comedogenic Rating
Rating: 0–1
PEG-18 is a small water soluble polymer that does not form an occlusive film or leave oily residue so it has very little tendency to block pores. Studies and anecdotal reports rarely link it to acne flare-ups which is why it sits at the bottom end of the comedogenic scale.
Suitable for acne prone and breakout prone skin in most cases.
Because PEG-18 can boost the penetration of other ingredients, any breakouts that do occur are more likely tied to heavier oils or actives in the same product rather than to PEG-18 itself.
Summary
PEG-18 serves mainly as a humectant and a solvent. Its chain of 18 ethylene oxide units grabs onto water molecules, pulling moisture into the upper layers of skin for a smooth hydrated feel. At the same time its balanced structure dissolves fragrances, lightweight oils and actives, helping formulas stay clear and stable while spreading evenly on skin.
The ingredient is a quiet workhorse rather than a star marketing claim so you will not always see it highlighted on the front label, yet it appears in a wide range of lotions, gels, cleansers and hair conditioners because it improves texture without heaviness.
Current research and decades of consumer use show PEG-18 to be low risk for irritation, sensitization or systemic toxicity when purified correctly. As with any new skincare product it is wise to perform a quick patch test before regular use to confirm personal tolerance.