What Is Peg-45?
Peg-45 is the short name for poly(oxy-1,2-ethanediyl), .alpha.-hydro-.omega.-hydroxy- with an average of 45 repeating ethylene oxide units. In simple terms it is part of the large PEG family, a group of water-loving polymers made by linking together small units of ethylene oxide. The number 45 tells us roughly how many of those units are strung together, which affects the thickness and moisture-holding power of the final ingredient.
Most Peg-45 used in cosmetics starts with plant-derived ethylene or petroleum-based feedstocks that are purified, then put through a controlled chemical reaction where ethylene oxide gas adds itself to a starter molecule such as water or glycerin. Each round of the reaction adds another link to the chain until the average length hits 45 units. The result is a waxy, white-to-off-white solid that dissolves easily in water and alcohol.
PEGs first appeared in personal care during the mid-20th century when formulators needed safer, more flexible replacements for heavy mineral oils. Because Peg-45 mixes with both water and oil, it soon found a spot in everything from classic cold creams to today’s lightweight gels.
You will often see Peg-45 in sheet masks, leave-on moisturizers, hydrating serums, anti-aging lotions, cleansing balms and hair conditioners. Its ability to bind ingredients, pull water to the skin and keep formulas stable makes it a go-to for products that need lasting moisture without a greasy feel.
Peg-45’s Cosmetic Benefits/Uses
Formulators turn to Peg-45 for several practical reasons that improve both the product and the user experience.
- Binding agent: Peg-45 helps hold powders, oils and water together so the product stays uniform from the first pump to the last squeeze. This keeps pigments evenly dispersed in tinted creams and prevents separation in lotions stored on the shelf.
- Humectant: As a moisture magnet Peg-45 attracts water from the environment and from deeper layers of the skin, giving formulas an instant hydration boost. This can make skin feel softer and look plumper after application.
- Solvent: Peg-45 dissolves fragrances, active extracts and oily residues, allowing them to blend smoothly into water-based systems. This means fewer gritty bits and a clearer, smoother final texture.
Who Can Use Peg-45
Peg-45 is generally gentle and works for most skin types. Dry skin benefits from its water-binding ability while normal and combination skin enjoy added softness without heavy residue. Oily or acne-prone skin can also use it because Peg-45 is lightweight and does not clog pores. Very sensitive skin may want to watch for redness if the finished product contains impurities from poor manufacturing but this is rare.
The ingredient is made from plant or petroleum sources and involves no animal parts so it is suitable for vegans and vegetarians.
Peg-45 is not known to harm pregnant or breastfeeding women when used on the skin but this is not medical advice. Anyone who is pregnant or nursing should ask a doctor before adding new products to a routine just to be safe.
The ingredient does not raise the skin’s sensitivity to sunlight and has no known limits on daytime use. It can also be used on the scalp and hair without special care.
Potential Side Effects/Adverse Reactions
Side effects from topical Peg-45 differ from person to person. The points below list possible issues yet most people will not notice any problems when the ingredient is used in a well-made product.
- Mild skin irritation such as redness or itching
- Stinging on very broken or freshly shaved skin
- Contact dermatitis in people with a confirmed PEG allergy
- Eye irritation if the product accidentally gets into the eyes
If you notice any of the reactions above stop using the product and consult a healthcare professional if symptoms do not fade quickly.
Comedogenic Rating
Comedogenic rating: 1 out of 5. Peg-45 is highly water soluble and does not leave an occlusive film, so it rarely traps sebum or dead cells in pores. Its lightweight humectant nature keeps it from acting like heavier oils or waxes that can trigger blockages. This makes the ingredient generally suitable for acne-prone or breakout-prone skin. Because Peg-45 can vary slightly in purity depending on the manufacturer, people with extremely reactive skin may still want to monitor how their skin responds, but true pore clogging is unlikely.
Summary
Peg-45 works mainly as a binder, humectant and solvent. It links water and oil phases for stable, uniform formulas, draws moisture to the skin for a softer feel and dissolves fragrances or actives so they disperse evenly. Thanks to these multitasking skills it appears in moisturizers, cleansers, masks and haircare, though it is not as headline grabbing as trendier botanicals. Overall safety data show a low risk of irritation or pore clogging, and regulatory bodies allow its use without strict limits. Still, everyone’s skin is unique, so when you introduce any new product containing Peg-45 it is wise to patch test first to be on the safe side.