Ingredient dictionary

PEG-45M

Also listed as: Polyethylene oxide

PEG-45M is a very large, water-soluble polymer made from linked ethylene oxide units. Its main job is to thicken a formula and add slip. It is on the label of 2 products in our library. Checked against our library November 6, 2026.

What PEG-45M does

Thickens water-based formulas
Improves slip and wet combing
Helps hair feel softer

PEG-45M belongs to the polyethylene glycol family and is made by linking many small ethylene oxide units into one very long chain. Its molecules are far larger than those of the light glycols used in many other formulas.

Formulators use it mainly as a thickener. Its long chains swell and tangle in water and raise the viscosity, so a shampoo feels fuller and pours more predictably. It also gives a slippery glide that helps hair feel softer and easier to comb when wet. Because it is meant for rinse-off products, it is not left on hair as a heavy layer.

Good for

Rinse-off hair products like shampoo, where it adds body and a smoother, softer feel.

Frequently asked questions

Is PEG-45M safe to use?

PEG-45M is generally well tolerated and is widely used in rinse-off hair products. Like any ingredient, it can occasionally bother someone with a sensitivity to it. If you have a reaction, stop using the product and check with a doctor.

Does PEG-45M cause hair buildup?

It is designed for rinse-off use, so it is meant to wash out with the shampoo rather than sit on hair. Buildup usually comes from heavy oils, waxes or silicones left on hair. If you use a clarifying shampoo from time to time, that can help keep hair light.