What Is Peg-4?
Peg-4 is a synthetic ingredient made by linking together small units of ethylene oxide to create a short chain of four units. The result is a clear liquid also known by its longer chemical name, Poly(oxy-1,2-ethanediyl), .alpha.-hydro-.omega.-hydroxy- (4 mol EO average molar ratio). It belongs to the large family of polyethylene glycols, often shortened to PEGs.
The use of polyethylene glycols in personal care dates back to the 1940s when chemists started looking for water-soluble compounds that could improve texture and stability in creams and lotions. Peg-4, with its very low molecular weight, proved useful because it mixes well with both water and many oils, helping formulas stay smooth and even.
Manufacturing begins with ethylene oxide, a gas derived from petroleum or plant-based ethanol. Under controlled pressure and temperature, the gas reacts with water. By stopping the reaction after four units have combined, producers obtain Peg-4. The process is tightly regulated to keep impurities like unreacted ethylene oxide to a minimum.
You will most often see Peg-4 in lightweight moisturizers, face masks, hydrating serums, after-sun gels, hair conditioners and cleansing wipes. Brands choose it when they want a product that feels fresh, absorbs quickly and leaves no oily film.
Peg-4’s Cosmetic Benefits/Uses
Peg-4 pulls its weight in a formula thanks to two key roles:
- Humectant – Peg-4 attracts water from the air and from deeper layers of skin, helping the upper surface stay hydrated. This can leave skin looking plumper and feeling softer for longer.
- Solvent – It dissolves other ingredients that would otherwise separate or form clumps, making the final product clear, stable and easy to spread.
Who Can Use Peg-4
Peg-4 suits most skin types including dry skin, oily skin and combination skin because it is light, water loving and non greasy. Those with very sensitive or compromised skin should check how they react since any synthetic solvent can occasionally trigger discomfort, but Peg-4 itself is not known to clog pores or leave a film.
The ingredient is produced from petroleum or plant derived ethanol and involves no animal sourced materials or by-products, so it is considered suitable for both vegans and vegetarians.
No data links Peg-4 to problems during pregnancy or while breastfeeding when used on the skin. This is not medical advice and anyone who is pregnant or nursing should ask a doctor before starting new skincare just to be safe.
Peg-4 does not make skin more sensitive to sunlight and there is no need for extra sun protection beyond your usual habits.
Potential Side Effects/Adverse Reactions
Side effects from topical Peg-4 vary from person to person. The points below list potential reactions but they are uncommon when the ingredient is used correctly in a well-formulated product.
- Skin irritation redness itching or a mild burning feeling, more likely on broken or very sensitive skin
- Contact dermatitis an allergic rash in people who develop sensitivity to polyethylene glycols
- Increased penetration of other ingredients which can amplify irritation if those ingredients are harsh
- Eye irritation watering or stinging if a product containing Peg-4 gets into the eyes
If any discomfort or unusual reaction appears stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
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Peg-4 is highly water soluble and leaves no oily residue on the skin so it does not block pores or create the conditions that foster blackheads or pimples. Its tiny molecular size means it is quickly rinsed away or evaporates with water loss reducing any chance of pore build-up.
For this reason Peg-4 is generally considered suitable for people who are prone to acne or frequent breakouts.
Keep in mind that the pore-clogging potential of a finished product depends on the entire formula not only on Peg-4.
Summary
Peg-4 is a short chain polyethylene glycol that acts as both a humectant and a solvent. It binds water to boost surface hydration and dissolves other ingredients so lotions stay clear smooth and easy to spread.
Although larger PEGs appear more often in cosmetics Peg-4 still enjoys steady use because it delivers a feather-light feel and mixes readily with water based systems.
Longstanding industry data shows Peg-4 is safe for topical use with only isolated reports of irritation or allergy. As with any new skincare ingredient a simple patch test is recommended before regular use especially for very sensitive skin.