What it is
Polysorbate 40 is made by esterifying sorbitol-derived sorbitan with palmitic acid and then ethoxylating it with about 20 units of ethylene oxide. The result is a mild, water-dispersible nonionic surfactant that lowers surface tension, allowing oil and water to form a stable emulsion or letting a small oil or fragrance load dissolve into a watery base. In sunscreens it helps keep the formula uniform and contributes to a light, fluid texture.
Safety & warnings
Polysorbate 40 is considered a mild, low-irritation nonionic surfactant and is widely used in leave-on and rinse-off products. As an ethoxylated ingredient it can theoretically carry trace 1,4-dioxane, which manufacturers control through purification. It is not a recognized fragrance allergen.
Origin & sourcing
Synthetic; manufactured from sorbitan (derived from sorbitol) esterified with palmitic acid and ethoxylated with ethylene oxide.
Questions everyone asks
Why is polysorbate 40 used in sunscreens?
It emulsifies and solubilizes, helping oil and water stay mixed and allowing small amounts of oils or fragrance to disperse evenly in a light formula.
Is polysorbate 40 the same as polysorbate 80?
They are related nonionic surfactants; the 40 version uses palmitic acid while the 80 version uses oleic acid, giving slightly different properties.