What is propanediol?

Propanediol (PDO) is a common ingredient in cosmetics and personal care products such as lotions, cleansers, and other skin treatments. It’s a chemical similar to propylene glycol, but thought to be safer.

However, there haven’t been enough studies yet to definitively determine safety. But considering current data, it’s most likely that topical PDO in cosmetics carries a low risk for serious problems.

PDO is currently approved for use in cosmetics, in restricted amounts, in the United States, Canada, and Europe. But does that mean it’s totally safe? We’ll lay out and analyze the evidence to help you make the right decision for you and your family.

PDO is a chemical substance either derived from corn or petroleum. It can be clear or very slightly yellow. It’s almost odorless. You’re likely to find PDO listed as an ingredient in pretty much any category of cosmetics and personal care products.

PDO has many household and manufacturing uses. It’s found in a variety of products, from skin cream to printer ink to auto antifreeze.

Cosmetic companies use it because it’s effective — and low cost — as a moisturizer. It can help your skin quickly absorb other ingredients in your product of choice. It can also help dilute other active ingredients.

According to the Environmental Working Group (EWG), you’ll find PDO most often in facial moisturizers, serums, and face masks. But you can also find it in other personal care products, including:

  • antiperspirant
  • hair color
  • eyeliner
  • foundation

Propanediol can be listed under several different names. The most common ones include:

  • 1,3-propanediol
  • trimethylene glycol
  • methylpropanediol
  • propane-1,3-diol
  • 1,3-dihydroxypropane
  • 2-deoxyglycerol

There are actually two distinct forms of PDO: 1,3-propanediol and 1,2-propanediol, also known as propylene glycol (PG). In this article, we’re talking about 1,3-propanediol, although these two chemicals are similar.

PG has recently received some negative press as a skin care ingredient. Consumer protection groups have raised concerns that PG can irritate eyes and skin, and is a known allergen to some.

PDO is thought to be safer than PG. And although the two chemicals have the exact same molecular formula, their molecular structures are different. That means they behave differently when used.

PG is associated with multiple reports of skin and eye irritation and sensitization, while the data on PDO is less harmful. So, many companies have begun to use PDO in their formulas instead of PG.

PDO is generally thought to be safe when absorbed through the skin in small amounts from topical cosmetics. Although PDO is categorized as a skin irritant, EWG notes that the health risks in cosmetics are low.

And after a panel of experts working for the Cosmetic Ingredient Review analyzed current data on propanediol, they found it to be safe when used in cosmetics.

In a study of topical propanediol on human skin, researchers only found evidence of irritation in a very low percentage of people.

Another study demonstrated that high-dose propanediol in oral form can have a fatal effect on lab rats. But, when rats inhaled a propanediol vapor, the test subjects showed no deaths or other serious irritation.

PDO has caused skin irritation, but not sensitization, in some animals and humans.

So, while some people might experience irritation after use, it doesn’t seem to cause an actual reaction. Additionally, PDO is less irritating than PG, which is known to sometimes cause allergic reactions.

There is one documented case of PDO contributing to the death of a person. But this case involved a woman intentionally drinking large amounts of antifreeze that contained PDO.

There’s no evidence that the small amounts of propanediol absorbed through the skin through cosmetics would lead to death.

No peer-reviewed studies have looked at PDO’s effect on human pregnancy as of yet. But when lab animals were given high doses of PDO, no birth defects or terminations of pregnancy occurred.

According to current data, using cosmetics or personal care products that contain low amounts of propanediol doesn’t pose much of a risk. A small population of people may have irritated skin after lots of exposure, but it doesn’t seem to be a risk for anything more serious.

Additionally, propanediol shows promise as a healthier alternative to propylene glycol as a skin care ingredient.