Ally asks…I’ve been seeing “propylene glycol free” on a lot of products lately together with ‘paraben free’ and ‘mineral oil free’. Googled it to see what’s so harmful about it and here found the Material Safety Data Sheet warns users to avoid skin contact with propylene glycol as this strong skin irritant can cause liver abnormalities and kidney damage’. If anyone could shed some light on the issue, would be much appreciated.
The Left Brain responds:
Propylene Glycol (or PG as we cosmetic scientists call it) is primarily used in beauty products to improve freeze-thaw stabilize of emulsions. A few percent or less of PG can prevent a cream or lotion from developing a grainy, cottage cheese-like texture when exposed to low temperatures. It also has moisturizing properties similar to glycerine (which is more commonly used.)
But PG, along with many other chemicals, has gotten a bad rap from groups like the EWG. For example, according to the website The Good Human the main role of PG is to “help any other chemicals that you come in contact with reach your bloodstream.” and that it “alters the structure of the skin by allowing chemicals to penetrate deep beneath it while increasing their ability to reach the blood stream.
That sounds pretty bad, doesn’t it? But let’s take a look at what science really says about propylene glycol in cosmetics.
Why is Propylene Glycol used in cosmetics?
As I noted above the main reason for using PG in cosmetics is to improve product texture. Relatively small amounts, on the order of 2% or less, are required to achieve this effect. To be fair, I should also point out that PG is used at higher concentrations in a few products where it acts as a solvent for other ingredients. But it is NOT primarily used to help other ingredients to penetrate into the blood stream.
Is Propylene Glycol dangerous in cosmetics?
According to the US Food & Drug Administration, propylene glycol is Generally Recognized As Safe (GRAS) for direct addition to food. It’s also permitted for use as a defoaming agent in indirect food additives. The Cosmetic Ingredient Review board (a group of scientists who review the safety of cosmetic ingredients) have determined that it’s ”safe for use in cosmetic products when formulated to be non-irritating.” Essentially this means that companies need to conduct skin irritation testing on new formulas to ensure PG doesn’t cause irritation when mixed with other ingredients. This is a standard test that companies do on new products so it’s not a big deal. (BTW, the testing is done on people, not animals.) In addition, many oral and IV drugs use significant amounts of PG. It’s my opinion that if an ingredient is safe for ingestion AND safe for use in injected drugs, it’s unlikely to cause any problems in a topical cosmetic.
But what about skin penetration?
Let me be clear: propylene glycol is one of the ingredients that penetrates skin but “absorption through the skin is minimal.” Since PG itself is safe to ingest (it’s either excreted in the urine or it breaks down in the blood to form lactic acid, which is naturally produced by your body, toxicity isn’t really an issue. The only cases where PG getting into the blood stream caused a problem occurred when PG-containing creams where applied to large areas of burned skin. That makes sense since burned skin would be missing the outer protective layer. In these cases mild lactic acidosis and serum hyperosmolality were observed. There are certainly no problems when low levels of PG are applied to healthy, intact skin.
How much is PG is ok?
According to a report issued by the World Health Organization, the estimated acceptable daily intake for PG is about 25 mg of propylene glycol per kg body weight. (Seventeeth Report of the FAO/WHO Expert Committee, 1974). For a 130 pound person that would be about 3 pounds of PG per day before you might have problems. That’s by ingesting it, you could put MUCH more on your skin since only a small amount actually penetrates through your skin into the blood stream.
What about penetration enhancement?
So PG is safe by itself but what about helping other ingredients get through the skin? This is the one question I couldn’t get a clear answer to. I couldn’t find any studies showing which ingredients PG enhances penetration and by how much. However, considering it’s used in relatively hight amounts in topical drug products it seems unlikely to me that it will cause problems at the lower levels used in most cosmetics.
The Beauty Brains bottom line
Its always good to be knowledgable about the chemicals you put in or on your body. But based on the the most recent scientific data it doesn’t look like there’s really much to be worried about cosmetics that contain propylene glycol.
Image credit: Wikipedia