#IngredientSpotlight: Propylene and Butylene Glycol

As natural extracts and ingredients gain popularity and preference in skincare, chemical ingredients unwittingly continue to get a lot of flak. While the negativity around chemicals in skincare is significantly justified, there are a lot of actually helpful chemicals that have just fallen prey to scaremongering. That’s why, we frequently put commonly used chemicals under the microscope to understand its purpose, benefits and threats. Today, we’re looking at propylene and butylene glycol – two highly popular compounds found in a variety of cosmetics and skincare products.

What are propylene and butylene glycol?

Chemically speaking, glycols are compounds that contain two OH (alcohol) groups. The difference between propylene and butylene glycol is that the former contains 3 carbon atoms and is therefore lighter, while the latter contains 4 carbon atoms making it larger in size. You may find propylene glycol and butylene glycol in products under the names ‘propanediol’ and ‘butanediol’ respectively.


Why is it used in skincare products?

Alcohol-based compounds (including glycerin) are mostly used in cosmetics and skincare products due to their humectant properties. Basically, they can hold onto water molecules and thus keep skin and hair hydrated.

Propylene glycol and butylene glycol are also popular penetration-enhancers. They break down ingredients that are water-insoluble and cannot be absorbed by the skin, thus improving the effectiveness of the product.

These compounds also have antimicrobial effects, so they extend the shelf-life of a product. Without these glycols, the end product would be a pricey, lumpy, non-uniform mess with a ridiculously limited expiry date.

They’re used in serums, sheet masks, cleansers, conditioners and hair-smoothening products due to their smooth and silky texture.

Propylene glycol is also prescribed to treat certain skin conditions like seborrheic dermatitis and ichthyosis.

Any side-effects?

Propylene and Butylene glycol get a lot of flak and scepticism because they’re derived from petroleum. It’s a common belief that anything that comes from petroleum is straight up toxic. However, these compounds and the quantities in which they’re used in skincare is what makes it harmful or not.

The fact that they’re penetration-enhancers means that they could also facilitate penetration of toxic compounds.Think about it this way: these chemicals take the active ingredients (stuff your skin needs) exactly where it’s supposed to be, thus improving your skin’s health. So it all comes down to the overall formulation.

There is however some concern over  Propylene glycol which  is known to cause irritation and allergies when used in high concentration. So you may watch out for this one. 

But, if your skincare product is designed to be gentle and non-irritating with safe natural actives, then the concentration of these chemicals will be adjusted accordingly for safe usage. In the end it comes down to the ethics of a company to make the product safe.

As always, do a patch test first! In case of super-sensitive skin or specific skin conditions, consult with your dermatologist before trying on a new product.


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