Polybutene Is Found in Many Skincare Products—But What Does It Do?

As we've grown more conscious about the beauty products we use, many of us have become devoted to decoding ingredient lists and percentages. On the whole, this is a good thing: It's important to be knowledgeable about formulas and hold brands accountable. There are, of course, some problems with this sudden emphasis on ingredients—namely, when certain ingredients are arbitrarily deemed "good" or "bad" for us.

Some ingredients just...are. In fact, there's an entire class of ingredients that have nothing to do with their skincare benefits at all. Rather, they bring something unique to the formula. Think: thickening agents, binders, solvents, and the like. They're ingredients we don't necessarily need to seek out or avoid as consumers, as they are far more important to cosmetic chemists and formulation specialists.

Still, it doesn't hurt to learn a bit more about these ingredients and how they work. Polybutene is a prime example of these formula-manipulating agents. Read on for everything you need to know about polybutene, according to the pros.

What is Polybutene?

Polybutene is a polymer, which refers to any natural or synthetic substance made up of very large molecules (called macromolecules) that are multiples of simpler chemical units called monomers. In this particular case, polybutene happens to be synthetic. The clear, colorless liquid polymer works as a binding, glossing, and thickening agent in cosmetics, explains Dr. Hirsch.

As Dr. Castilla points out, its large particle size is unable to penetrate the outer layer of skin, making it an ideal viscosity controller and binding agent. Plus, polybutene is generally non-sensitizing and non-comedogenic, so there's really no major downside in adding it to any given formulation.

While it's primarily used to create a specific viscosity (which is why you'll find polybutene in many lip gloss and oil formulations), Dr. Castilla says it can also act as a binder to hold ingredients together within creams and types of makeup. And, thanks to its naturally sticky consistency, polybutene is also sometimes used in face and body hair depilatories.

Benefits of Polybutene for Skin

• Holds ingredients together: Polybutene is often used as a binding agent, says Dr. Hirsch, allowing the cohesion of different cosmetic ingredients within a single formula.
• Increases viscosity: Both doctors are quick to point out polybutene's chief function as a non-aqueous thickening agent, meaning it thickens formulas by targeting oils rather than water.
• Softens and smoothes skin: According to Dr. Castilla, polybutene functions as an emollient when used in moisturizers since it increases the thickness of lipids.
• Can act as an epilating agent: Because polybutene has a naturally sticky consistency, it's sometimes used as an epilator to remove unwanted hair.
• Adds shine and gloss: Polybutene's thickening properties also make it a great ingredient for adding shine and gloss to cosmetic products, according to Dr. Castilla.

Part of the reason polybutene is so widely used in cosmetic products is that it's so neutral on the skin. According to Dr. Castilla, the ingredient is non-sensitizing and non-comedogenic and works well with virtually any ingredient. In addition, polybutene naturally has very little odor and is completely clear, meaning it won't change the look or smell of a product. But, as mentioned, polybutene cannot penetrate the outer layers of the skin (due to its large particle size), so there aren't any real benefits to the skin.

Side Effects of Polybutene

Lest we forget, polybutene's large size prevents it from penetrating the skin, so it can be used multiple times throughout the day without any issue. And since it won't sensitize skin or clog pores, there aren't any real side effects to worry about.

It was determined to be safe for use in cosmetic products by the Cosmetic Ingredient Review (CIR) Expert Panel back in 2008—the Expert Panel noted the large, mostly insoluble polymer produced no adverse effects in a range of clinical studies, leading to its conclusion that polybutene does not present any risks when used at concentrations of 4% or lower.

How to Use It

Both experts agree: Polybutene isn't an ingredient with any significant benefit (or risks), so it shouldn't be something you look for in cosmetic products. Rather, polybutene would be of far more concern to a formulation chemist.

The Final Takeaway

There's an overwhelming sense of hypervigilance when it comes to cosmetic ingredients these days. Luckily, polybutene is one ingredient you don't have to worry about. Leave it to the trusted cosmetic and formulation chemists; they're the experts, after all.