Defining Ingredients

What is Propylene Glycol (PG) ?

July 3, 2017

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Propylene Glycol is in cosmetics, processed foods, shampoos, lotions, perfumes, deodorants, over the counter drugs, and much more. You may have seen Propylene Glycol listed as 1,2-propanediol, PG, methyl glycol, trimethyl glycol. 

Propylene Glycol is NOT ethylene glycol. I’ll get into lethal ethylene glycol next week.

 

According to the FDA Code of Federal Regulations, Propylene Glycol (1,2,-propanediol) is described to not occur in nature and is made by “treating propylene with chlorinated water to form the chlorohydrin which is converted to the glycol by treatment with sodium carbonate solution. It is also prepared by heating glyercol with sodium hydroxide.” 

The FDA recognizes Propylene Glycol as “Generally Recognized As Safe” (GRAS) when used as a food additive.

Propylene Glycol uses include:

  • Anti-caking agent
  • Antioxidant 
  • Dough strengthener
  • Emulsifier
  • Flavor agent
  • Formulation aid
  • Humectant (moisture preserver)
  • Processing aid
  • Solvent and vehicle
  • Stabilizer and thickener
  • Surfactant
  • Texturizer

Fun fact: The FDA prohibits the use of Propylene Glycol in cat food. (FDA)

The World Health Organization (WHO) describes propylene glycol as “…relatively safe in normal use, but cases of poisoning associated with its use as a vehicle for drugs or vitamins given intravenously or orally have been described.”

PubChem describes propylene glycol as a “synthetic liquid substance that absorbs water”. Additional uses of propylene glycol are listed as:

  • De-icing agent (think: airplanes)
  • Polyester compound
  • Antifreeze when leakage may lead to food contact
  • To create artificial smoke for theatrics or firefighting training

Let’s look at the health concerns of Propylene Glycol.

Agency for the Toxic Substances and Disease Registry ATSDR:

  • Affected Organ Systems: 
    • Dermal (Skin)
    • Renal (Urinary System or Kidneys)
    • Respiratory (From the Nose to the Lungs)
  • Cancer Category: None

Human Metabolome Database:

  •  Development of serum hyperosmolality
  • Lactic acidosis
  • Kidney failure

Propylene glycol breaks down in the body in about 48 hours. However, studies of people and animals show that if you have repeated eye, skin, nasal, or oral exposures to propylene glycol for a short time, you may develop some irritation. (ATSDR)

What about Propylene Glycol Esters in Cosmetics?

The Cosmetics Ingredient Review (CIR) Expert Panel concluded…

“…the following ingredients are safe in the present practices of use and concentration described in this safety assessment in cosmetics:

propylene glycol behenate*
propylene glycol caprylate* propylene glycol cocoate*
propylene glycol dicaprate
propylene glycol dicaproate propylene glycol dicaprylate propylene glycol dicaprylate/dicaprate propylene glycol dicocoate* propylene glycol diethylhexanoate propylene glycol diisononanoate* propylene glycol diisostearate* propylene glycol dilaurate*

propylene glycol dioleate propylene glycol dipelargonate propylene glycol distearate* propylene glycol diundecanoate*

propylene glycol heptanoate*
propylene glycol linoleate*
propylene glycol linolenate*
propylene glycol isostearate
propylene glycol laurate
propylene glycol myristate
propylene glycol oleate
propylene glycol oleate SE (self-emulsifying)* propylene glycol stearate

propylene glycol stearate SE
soybean oil propylene glycol esters* almond oil propylene glycol esters* apricot kernel oil propylene glycol esters* avocado oil propylene glycol esters* olive oil propylene glycol esters*

*Were ingredients in this group not in current use to be used in the future, the expectation is that they would be used in product categories and at concentrations comparable to others in this group.

If you’re interested in reading the entire CIR document on Propylene Glycol Esters, click here.

The Bottom Line…

Government regulations recognize Propylene Glycol to be generally safe in pharmaceuticals and foods. It is considered to be toxic in large doses. Toxic effects include hyperosmolality, increased anion gap metabolic acidosis (due to lactic acidosis), acute kidney injury, and sepsis-like syndrome. Due to it’s unnatural origin, I think I’ll pass on Propylene Glycol when possible.

 

Have questions about other questionable ingredients? Browse my Ingredients Defined page for answers.

 

 

Resources:

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=184.1666

http://www.who.int/ipcs/publications/training_poisons/basic_analytical_tox/en/index11.html

https://pubchem.ncbi.nlm.nih.gov/compound/1_2-propanediol#section=Top

https://www.atsdr.cdc.gov/substances/toxsubstance.asp?toxid=240

http://www.hmdb.ca/metabolites/HMDB01881

https://www.ncbi.nlm.nih.gov/pubmed/17555487

http://www.cir-safety.org/sites/default/files/PGEste_092014_Tent_for%20posting.pdf

http://online.personalcarecouncil.org/ctfa-static/online/lists/cir-pdfs/PR560.PDF

https://www.atsdr.cdc.gov/phs/phs.asp?id=1120&tid=240

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