Propylene Glycol Chemical Properties And Reference Information

Information On Propylene Glycol From Wikipedia

Propylene glycol (IUPAC name: propane-1,2-diol) is an organic compound with the chemical formula CH3CH(OH)CH2OH. It is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Containing two alcohol groups, it is classed as a diol. It is miscible with a broad range of solvents, including water, acetone, and chloroform. In general, glycols are non-irritating, have very low volatility and very low toxicity.

It is produced on a large scale primarily for the production of polymers. In the European Union, it has the E-number E1520 for food applications. For cosmetics and pharmacology, the number is E490. Propylene glycol is also present in propylene glycol alginate, which is known as E405. Propylene glycol is a compound which is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA) under 21 CFR x184.1666 and is also approved by FDA for certain uses as an indirect food additive. Propylene glycol is approved and used as a vehicle for topical, oral and some intravenous pharmaceutical preparations in U.S. and in Europe.


Forty-five percent of propylene glycol produced is used as chemical feedstock for the production of unsaturated polyester resins. In this regard, propylene glycol reacts with a mixture of unsaturated maleic anhydride and isophthalic acid to give a copolymer. This partially unsaturated polymer undergoes further crosslinking to yield thermoset plastics. Related to this application, propylene glycol reacts with propylene oxide to give oligomers and polymers that are used to produce polyurethanes. Propylene glycol is used in waterbased acrylic architectural paints to extend dry time which it accomplishes by preventing the surface from drying due to its slower evaporation rate compared to water.


Propylene glycol is also used in various edible items such as coffee-based drinks, liquid sweeteners, ice cream, whipped dairy products and soda. Vaporizers used for delivery of pharmaceuticals or personal-care products often include propylene glycol among the ingredients. In alcohol-based sanitizers, it is used as a humectant to prevent the skin from drying. Propylene glycol is used as a solvent in many pharmaceuticals, including oral, injectable, and topical formulations. Many pharmaceutical drugs which are insoluble in water utilize PG as a solvent and carrier; benzodiazepine tablets are one example. PG is also used as a solvent and carrier for many pharmaceutical capsule preparations. Additionally, certain formulations of artificial tears use proplyene glycol as an ingredient.


The freezing point of water is depressed when mixed with propylene glycol. It is used as aircraft de-icing fluid. Water-propylene glycol mixtures dyed pink to indicate the mixture is relatively nontoxic are sold under the name of RV or marine antifreeze. Propylene glycol is frequently used as a substitute for ethylene glycol in low toxicity, environmentally friendly automotive antifreeze. It is also used to winterize the plumbing systems in vacant structures. The eutectic composition/temperature is 60:40 propylene glycol:water/-60 °C. The −50 °F/−45 °C commercial product is, however, water rich; a typical formulation is 40:60.

Miscellaneous Applications

Propylene glycol (often abbreviated 'PG') has many applications. Some common applications see PG used:

  • As a solvent for many substances, both natural and synthetic.
  • As a humectant (E1520).
  • In veterinary medicine as an oral treatment for hyperketonaemia in ruminants.
  • In the cosmetics industry, where PG is very commonly used as a carrier or base for various types of makeup.
  • For trapping and preserving insects (including as a DNA preservative).
  • For the creation of theatrical smoke and fog in special effects for film and live entertainment. So-called 'smoke machines' or 'hazers' vaporize a mixture of PG and water to create the illusion of smoke. While many of these machines use a PG-based fuel, some use oil. Those which use PG do so in a process which is identical to how electronic cigarettes work; utilizing a heating element to produce a dense vapor. The vapor produced by these machines has the aesthetic look and appeal of smoke, but without exposing performers and stage crew to the harms and odors associated with actual smoke.
  • As an additive in PCR to reduce the melting temperature of nucleic acids for targeting of GC rich sequences.

Propylene Glycol Kills Viruses 

Propylene Glycol (90% aqueous solution) inactivates (kills) the influenza virus within 3 minutes. It has been found that propylene glycol vapor dispersed into the air of an enclosed space produces a marked and rapid bactericidal effect on microorganisms introduced into such an atmosphere in droplet form. Concentrations of 1 gm. of propylene glycol vapor in two to four million cc. of air produced immediate and complete sterilization of air into which pneumococci, streptococci, staphylococci, H. influenzae, and other microorganisms as well as influenza virus had been sprayed.

Does Propylene Glycol Kill Bacteria?

The test concluded that air containing propylene glycol kills off bacteria of all kinds, including disease-causing ones and that PG vapour is invisible, odourless, and non-irritating. It added that PG is essentially non-toxic. Read more here.

Information About Propylene Glycol From PubChem 

Propylene glycol is a synthetic liquid substance that absorbs water. Propylene glycol is also used to make polyester compounds, and as a base for deicing solutions. Propylene glycol is used by the chemical, food, and pharmaceutical industries as an antifreeze when leakage might lead to contact with food. The Food and Drug Administration (FDA) has classified propylene glycol as an additive that is “generally recognized as safe” for use in food. It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products. It is a solvent for food colors and flavors, and in the paint and plastics industries. Propylene glycol is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions. Other names for propylene glycol are 1,2-dihydroxypropane, 1,2-propanediol, methyl glycol, and trimethyl glycol. Propylene glycol is clear, colorless, slightly syrupy liquid at room temperature. It may exist in air in the vapor form, although propylene glycol must be heated or briskly shaken to produce a vapor. Propylene glycol is practically odorless and tasteless.

Propylene Glycol Uses

Propylene glycol is a synthetic liquid substance that absorbs water. Propylene glycol is also used to make polyester compounds, and as a base for deicing solutions. Propylene glycol is used by the chemical, food, and pharmaceutical industries as an antifreeze when leakage might lead to contact with food. Read more here. Learn about the antiviral activity of propylene glycol here.

About Food Grade Propylene Glycol

Propylene glycol is a synthetic liquid substance that absorbs water and maintains moisture in food products.  The Food and Drug Administration (FDA) has classified propylene glycol as an additive that is "generally recognized as safe" for use in food. Food grade propylene glycol is used in food, hair care products, skin care products. Food grade proylene glycol is used as a laxative to treat constipation for dogs and cats. It is also used to empty the intestines prior to diagnostic procedures. It is commonly used in humans before diagnostic procedures such as colonoscopy.  Propylene glycol (PG) is one of the least toxic glycols.  

Propylene Glycol For Dogs

Food grade propylene glycol is used in dog food animal health care products.  Food grade proylene glycol is used as a laxative to treat constipation for dogs and cats. It is also used to empty the intestines prior to diagnostic procedures. It is used in popular dog food brands and dog treats.  Propylene glycol is used to clean a dog's ears because it moisturizes, removes ear wax and is a weak anti-fungal agent. 

Propylene Glycol For Animal Health Care

Propylene Glycol is given for the prevention and treatment of Ketosis in dairy cattle. In veterinary medicine, it is also used as as a solvent for many pharmaceuticals.  In veterinary medicine propylene glycol is used for the treatment of acetonaemia and ketosis.  In the pharmaceutical industry it is used as a solvent and as a stabilizing agent for vitamin preparations.  It is also used as an excipient in a large number of parenteral and topical medicinal products, particularly for drugs which are unstable or insoluble in water.

Propylene Glycol For Goats

Propylene Glycol is used to treat Pregnancy Toxemia/ Ketosis in female goats. It is an appetite suppressant and it inhibits rumen bacteria in goats.  Goat Ketosis is treated by administering propylene glycol.

Common Uses of Propylene Glycol

Propylene glycol is an organic compound. It is a viscous, colorless liquid that is almost odorless. It does have a faint sweet taste. Generally, glycols are non-irritating, have low volatility and very low toxicity. It is found in a wide variety of products in the food, drug, cosmetic, and manufacturing industry. PG is considered generally safe for use in foods by the FDA. Propylene glycol has many uses in the food industry. It is an anti-caking agent which helps prevent food from sticking together and forming clumps. It is an antioxidant, so it extends the shelf life of food. It strengthens dough and preserves moisture. Food grade propylene glycol can also be used to thicken food components and change the appearance of a food. PG is a great carrier, it dissolves other food additives or nutrients to be used in processing, like flavors or antioxidants.  Propylene glycol is used in food, hair conditioner, skin care products and antifreeze.  PG is a synthetic liquid that belongs to the same chemical class as alcohol. It is different than ethylene glycol.

Propylene glycol is used for trapping and preserving insects. It is used as a humectant. Propylene glycol is used in a range of oral, topical and intravenous medicines. It is also used as a drug stabilizer. 

Propylene glycol is used in alcoholic beverages, baked goods, cheese, chewing gum, confection, frosting, fats, oils, frozen dairy, fruit juice, gelatin, pudding, gravies, hard candy,  meat products, milk products, nonalcoholic beverages, grain, poultry, processed vegetables, reconstituted vegetables, snack foods, soft candy, sweet sauce.

Propylene glycol is used in industrial applications such as hydraulic fluids, rubber lubricants, antifoam agents, intermediates in urethane foams, adhesives, coatings, elastomers, plasticizers, paint formulations, laboratory reagents. It is a solvent for vegetables, oils, waxes and resins.

In the cosmetic industry it is a great wetting agent. Propylene glycol helps the skin retain moisture. It enhances the ability of cosmetic creams to spread across the surface of the skin. In the cosmetic industry it is used in more than 4,000 products and formulas. Propylene glycol has a long history and has been used in a variety of applications. In the drug industry it is used as a drug solubilizer in different medications. In vitamins it is used as a stabilizer. Industrial uses for propylene glycol include; making other materials like unsaturated polyester resins, manufacturing paints, foams, and coatings.

Food Grade/ USP Grade Propylene Glycol Used in the Botanical Industry

It is considered a sugar alcohol and it is not intoxicating. Propylene glycol is used for its emulsifying properties. Without propylene glycol the ingredients would not mix with one another. PG is able to keep the ingredients in suspension.

How Propylene Glycol is Used in Food

There is a lot of misconception around propylene glycol and its role in food. First it is important to know the difference between Propylene glycol and ethylene glycol. Ethylene glycol is very toxic and is harmful to humans. These two chemicals are not the same and, in many cases, companies are now replacing the use of ethylene glycol with propylene glycol because PG is safe and non-toxic. Propylene glycol is a common ingredient found in many products. It is used in products such as baked goods, frostings, and candies. It helps to evenly distribute the flavoring throughout the product. Propylene glycol is a generally recognized as safe (GRAS) food ingredient. It was classified by the FDA in 1973. Propylene glycol can maintain moisture in food, and it works to maintain the flavor quality for longer periods of time. The FDA regulates how propylene glycol is used in food consumption. They set limits on the uses and amounts that can be safely used in food.

Propylene glycol is water-soluble, and it is synthetic and easily metabolized by the liver into normal products of the citric acid metabolic cycle. 45% of PG that is ingested is secreted directly from the body and does not come into contact with the liver. Many articles try to scare consumers away from using PG because it is an ingredient in “antifreeze”. Antifreeze is a scientific word used to describe the lowering of the freezing point of a liquid. Another example of this would be how salt is used to melt the snow and ice from the roads and walkways. The salt lowers the freezing point of water. This is a safe chemical that is being used as antifreeze. The overall take away is that propylene glycol is safe to use in food and it is safe to consume. Propylene glycol is used in flavored iced tea, ice cream, packaged frostings, boxed cake mix, food coloring, salad dressing, and more. It is a great ingredient and raises no concern. The levels it is consumed at are below the safe limit. Lab Alley has propylene glycol for sale online, they offer fast shipping in the USA.

How Propylene Glycol Used in Hair Products

Propylene glycol has many uses. The cosmetic industry has found many great ways to utilize this product. Lab Alley has cosmetic grade propylene glycol for sale online. They offer fast shipping in the USA. Propylene glycol is known as 1,2-propanediol. It is a safe, vegetable-based synthetic and it attracts water. Because it is able to attract water, PG functions as a humectant. It is used as an ingredient in moisturizers in order to reduce flaking and restoring suppleness. When it is used in products it absorbs excess water, which reduces bacteria and helps the products last longer. Propylene glycol can be found in shampoo, conditioners, and leave-in styling products. It is very versatile and can fulfill many purposes in the hair products. Because propylene glycol is a humectant it is great for moisturizing the hair when it is used with water. Propylene glycol is recognized as safe for use in cosmetics, food, and medicine.

How Propylene Glycol is Used in Skin Care

Propylene Glycol is a common ingredient in skin care. It is a hydrating and delivery ingredient used in skin care products. Research from toxicologists show that PG does not present a health risk when used in cosmetics and skin care. Propylene glycol is used in small amounts as an ingredient in skin care, it helps keep the products lasting longer on the shelf. PG can prevent the product from developing a grainy texture when exposed to low temperatures. Propylene glycol is an organic alcohol and it is used as a skin condition agent. PG attracts water and it is used in moisturizers to enhance the skin. The Cosmetic Ingredient Review Board determined that propylene glycol is “safe for use in cosmetic products when formulated to be non-irritating”. Based on the most recent research propylene glycol is safe and using products that contain PG does not pose any threats. Lab Alley sells propylene glycol in various quantities. Lab Alley provides fast shipping in the USA.

Propylene Glycol Side Effects

Propylene glycol is considered generally safe by the FDA. Most creams that have PG in them are safe to use and they have no side effects. However, stinging, burning, redness, or irritation may occur. Serious allergic reactions to PG are rare. If you experience rash, sweating, or loose bowl movements you are probably allergic to propylene glycol. Propylene glycol is found in many everyday products like shampoo, deodorant, and lotions. Normal use of the products is not dangerous or toxic. But prolonged or excessive use can cause redness and itching to the skin.

Propylene glycol is not safe for infants or pregnant women. Infants can not break down propylene glycol as quickly as an adult. When we eat food that has propylene glycol in it 45% will be excreted by the kidneys but the rest is broken down in the body into lactic acid. The buildup of lactic acid can lead to acidosis and kidney failure. Acidosis occurs when the body can’t get rid of the acid fast enough. It then builds up in the blood and interferes with proper functioning. Although cases of toxicity are rare and usually only occur when someone consumes high doses of medicine that contains propylene glycol. The FDA does recognize propylene glycol as generally safe in proper proportions.

Propylene Glycol Structure

The chemical formula for PG is CH3CH(OH)CH2OH it is a viscous, colorless liquid. It contains two alcohol groups. It mixes with a wide range of solvents. It is produced on a large scale and it is used in the production of polymers. It is sometimes called a-propylene glycol. Propylene glycol is also known as propane-1, 2-diol. It is an organic compound, and it has many applications. If you would like to view the structural formula or the molecular model, click here.

Propylene Glycol Alginate

Propylene glycol alginate is used many ways in food products. It is an ester of propylene glycol and alginic acid. It is an emulsifier, stabilizer, and thickener. PGA is obtained from algae and its chemical formula is C9H14O7. Propylene glycol alginate is soluble in water and it is a stabilizer for the foam head on beer, salad dressing, frozen custard, cheese, non carbonated fruit drinks and frozen milk deserts.

How Propylene Glycol is Used in Antifreeze

Antifreeze is an additive that lowers the freezing point of a water-based liquid. Water and antifreeze are used in combustion engines and other heat transfer applications. The purpose is to prevent an enclosure from bursting due to expansion. Propylene glycol is commonly used in antifreeze because it is considerably less toxic than ethylene glycol. It is referred as “non-toxic antifreeze”. Propylene glycol is used as an ingredient in antifreeze and it is a safer option than ethylene glycol. PG is generally regarded as safe by the FDA.