PEG-40

PEG-40 is a polyethylene glycol—a synthetic polymer created by condensing ethylene oxide with water. It belongs to a family of ingredients widely used across cosmetics and pharmaceuticals for their ability to attract and retain water.In skincare formulations, PEG-40 primarily functions as a humectant (drawing moisture into the skin) and a solvent (helping to dissolve and stabilise other active ingredients). It is found in roughly 0.1% of skincare products, often appearing in serums, creams, and treatment products.

PEG-40 is hydrophilic, meaning it has a strong affinity for water molecules. When applied to skin, it draws moisture towards the skin surface and helps prevent water loss, thereby supporting hydration. Because it is also a solvent, it can dissolve ingredients that would otherwise be insoluble in typical skincare bases, making it easier to formulate products with a wider range of actives.The polymer's structure allows it to be both water-soluble and compatible with many other ingredients, which is why it appears frequently in multi-active formulations.

PEG-40 is typically used as a supporting ingredient rather than a primary active, so you will rarely need to use it in isolation. Simply apply products containing PEG-40 as directed. Because it works as a humectant, it performs best when applied to damp skin (or followed by a moisturiser) to maximise its water-binding effect. It mixes well with other skincare ingredients, so there are few compatibility concerns.

PEG-40 and related polyethylene glycols are generally well-tolerated in cosmetic formulations. Rare contact sensitivity has been reported with some PEG derivatives in specific individuals; if you experience redness or irritation, discontinue use.