PEG-100

PEG-100 is a polyethylene glycol—a synthetic polymer derived from petroleum. In skincare, it functions as both a solvent (helping ingredients dissolve and mix) and a humectant (attracting water to the skin). It belongs to a family of PEG compounds used across cosmetics, pharmaceuticals and personal care at varying molecular weights.Lower molecular weight PEGs like PEG-100 are particularly valued in formulations for their ability to improve texture, stability and skin penetration of active ingredients. They're commonly paired with other emulsifiers to create stable creams and serums.

PEG-100 works through two mechanisms. As a humectant, it has a hygroscopic nature—meaning it attracts and binds water molecules, drawing them from deeper skin layers and the air into the outer epidermis. This hydration effect is dose-dependent; higher concentrations may have stronger hygroscopic effects.As a solvent, PEG-100 allows otherwise incompatible ingredients to mix together, improving formulation homogeneity. This also means it can enhance penetration of other ingredients into the skin, which is why it's sometimes included as a 'skin penetration enhancer' in formulations.

PEG-100 is typically used as a minor ingredient within formulations rather than as a standalone treatment. It's most effective when part of a well-formulated moisturiser or serum. If using a product containing PEG-100, consistency matters; daily use will provide more noticeable hydration benefits than occasional application. It works well alongside other humectants like glycerin or hyaluronic acid, as multiple humectants can enhance overall hydration.

PEG-100 is generally well-tolerated in topical skincare. Some individuals with very sensitive skin or those prone to irritant reactions may wish to patch-test products containing it first, particularly if the product also contains other potentially sensitising ingredients.