PEG-4 Bon Humectant No known benefits PEG-4 at a glance Type of polyethylene glycol Used as a humectant and solvent in cosmetics Ruled safe for use in skin care Highest concentration (20%) is used in manicure preparations PEG-4 description PEG-4 is a polyethylene glycol used as a lightweight humectant (an ingredient which attracts and holds moisture to skin) and solvent in skin care products. The safety of PEG in its various forms has recently been questioned. The primary concern is that they can contain problematic impurities such as ethylene oxide and 1,4 dioxane. Both are by-products from the manufacturing process, not something natural to any form of PEG. Although this was once a concern, reputable cosmetic ingredient suppliers have long since eliminated these impurities from the finished ingredient, which makes PEGs safe for skin. As for PEG-4 specifically, the independent Cosmetic Ingredient Review board has deemed it safe in its current use. The highest concentration included in cosmetics is 20%, in some manicure preparations. Related ingredients: PEG