Propylene glycol (along with other glycols and glycerol) is a humectant or humidifying and delivery ingredient used in cosmetics, meaning it helps other ingredients absorb better into the skin. Despite research to the contrary, you can find Web sites and spam e-mails stating that propylene glycol is really industrial antifreeze and the major ingredient in brake and hydraulic fluids. These sites also state that tests show it to be a strong skin irritant. They further point out that the Material Safety Data Sheet (MSDS) on propylene glycol warns users to avoid skin contact because systemically (in the body) it can cause liver abnormalities and kidney damage.
As ominous as that sounds, it is so far from the reality of cosmetic formulations that almost none of it holds any water or poses real concern. It is important to realize that the MSDS sheets are talking about 100% concentrations of a substance. Even water and salt have frightening comments regarding their safety according to their MSDS reports. It is true that propylene glycol in 100% concentration is used as antifreeze, but—and this is a very big but—in cosmetics it is used in only the smallest amounts to keep products from melting in high heat or freezing when it is cold. It also helps active ingredients penetrate the skin. In the minute amounts used in cosmetics, propylene glycol is not a concern in the least. Women are not suffering from liver problems (as some Web sites have asserted) because of propylene glycol in cosmetics.
And finally, according to the U. S. Department of Health and Human Services, within the Public Health Services Agency for Toxic Substances and Disease Registry, “studies have not shown these chemicals [propylene or the other glycols as used in cosmetics] to be carcinogens” (Source: www. atsdr. cdc. gov).
Polyethylene glycol (PEG) is another ingredient “natural” Web sites have attempted to make notorious. They gain a great deal of attention by attributing horror stories to PEG. For example, several Web sites state the following: “Because of their effectiveness, PEGs are often used in caustic spray-on oven cleaners, yet are also found in many personal care products. Not only are they potentially carcinogenic, but they contribute to stripping the skin’s Natural Moisture Factor, leaving the immune system vulnerable.” There is no research substantiating any of this. Quite the contrary: PEGs have no known skin toxicity. The only negative research results for this ingredient group indicate that large quantities given orally to rats can cause tumors. How that got related to skin-care products is a mystery to me.