CAS Number: 57-55-6
EC Number: 200-338-0
E number: E1520 (additional chemicals)
Chemical formula: C3H8O2
Molar mass: 76.095 g·mol−1
Propylene glycol (IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste.
Propylene glycols chemical formula is CH3CH(OH)CH2OH.
Containing two alcohol groups, it is classed as a diol.
Propylene glycol is miscible with a broad range of solvents, including water, acetone, and chloroform.
In general, glycols are non-irritating and have very low volatility.
Propylene glycol is a substance commonly used as a food additive or ingredient in many cosmetic and hygiene products.
Propylene glycol is produced on a large scale primarily for the production of polymers.
In the European Union, it has 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 GRAS (generally recognized as safe) by the US Food and Drug Administration under 21 CFR x184.1666, and is also approved by the 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 the U.S. and in Europe.
Propylene glycol is uses in:
food and tobacco products
heat transfer and hydraulic fluids
other applications (smoke screen, smoke simulator, etc.)
Forty-five percent of propylene glycol produced is used as a 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 water-based 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.
Food and drug:
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 hand 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 propylene glycol as a solvent and carrier; benzodiazepine tablets are one example.
Propylene glycol is also used as a solvent and carrier for many pharmaceutical capsule preparations.
Additionally, certain formulations of artificial tears use propylene glycol as an ingredient.
Propylene glycol is commonly used to de-ice aircraft.
The freezing point of water is depressed when mixed with propylene glycol.
Propylene glycol is used as aircraft de-icing and anti-icing fluid.
A 50% water-diluted and heated solution is used for removal of icing accretions from the fuselages of commercial aircraft on the ground (de-icing), and 100% undiluted cold solution is used only on wings and tail surfaces of an aircraft in order to prevent ice accretion from forming during a specific period of time before takeoff (anti-icing).
Normally, such time-frame is limited to 15–90 minutes, depending on the severity of snowfall and outside air temperature.
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.
Propylene glycol 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.
Electronic cigarettes liquid:
A bottle of flavored e-liquid for vaping shows propylene glycol as one of the main ingredients along with vegetable glycerin.
Propylene glycol, glycerin, or a mixture of both, are the main ingredients in e-liquid used in electronic cigarettes.
They are aerosolized to resemble smoke and serve as carriers for substances such as nicotine and flavorants.
As a solvent for many substances, both natural and synthetic.
As a humectant (E1520).
As a freezing point depressant for slurry ice.
In veterinary medicine as an oral treatment for hyperketonaemia in ruminants.
In the cosmetics industry, where propylene glycol 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.
While many of these machines use a propylene glycol-based fuel, some use oil.
Those which use propylene glycol do so in a process that 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.
as a surfactant, Propylene glycol is used to prevent water from beading up on objects.
Propylene glycol is used in photography for this purpose to reduce the risk of water spots, or deposits of minerals from water used to process film or paper.
What Is Propylene Glycol?
Propylene glycol is a synthetic food additive that belongs to the same chemical group as alcohol.
Propylene glycol is a colorless, odorless, slightly syrupy liquid that is a bit thicker than water.
Propylene glycol has practically no taste.
Additionally, Propylene glycol can dissolve some substances better than water and is also good at retaining moisture.
This makes Propylene glycol very useful as a food additive, so it can be found in a wide variety of processed foods and drinks.
Other names it is known by include:
Methyl ethyl glycol
Propylene glycol is sometimes confused with ethylene glycol, as both have been used in antifreeze due to their low melting points.
However, these are not the same substance.
Ethylene glycol is highly toxic to humans and is not used in food products.
Propylene glycol is a synthetic liquid that’s used for a variety of purposes in the pharmaceutical, cosmetics, food and manufacturing industries.
Propylene glycol is typically odorless, tasteless, and colorless and its texture is somewhat oily or syrupy.
ECHA InfoCard: 100.000.307
EC Number: 200-338-0
E number: E1520 (additional chemicals)
PubChem CID: 1030
RTECS number: TY6300000
CompTox Dashboard (EPA): DTXSID0021206
Where and How Is Propylene glycol Used?
Propylene glycol is commonly used as an additive to aid in the processing of foods and improve their texture, flavor, appearance and shelf life.
In foods, propylene glycol may be used in the following ways:
Anti-caking agent: Propylene glycol helps prevent food components from sticking to one another and forming clumps, such as in dried soups or grated cheese.
Antioxidant: Propylene glycol extends the shelf life of foods by protecting them against deterioration caused by oxygen.
Carrier: Propylene glycol dissolves other food additives or nutrients to be used in processing, such as colors, flavors or antioxidants.
Dough strengthener: Propylene glycol modifies the starches and gluten in dough to make it more stable.
Emulsifier: Propylene glycol prevents food ingredients from separating, such as oil and vinegar in salad dressing.
Moisture preserver: Propylene glycol helps foods maintain a stable level of moisture and stops them from drying out. Examples include marshmallows, coconut flakes and nuts.
Processing aid: Propylene glycol is used to enhance the appeal or the use of a food, for example, to make a liquid clearer.
Stabilizer and thickener: Propylene glycol can be used to hold food components together or thicken them during and after processing.
Texturizer: Propylene glycol can change the appearance or mouthfeel of a food.
Propylene glycol is commonly found in many packaged foods, such as drink mixes, dressings, dried soups, cake mix, soft drinks, popcorn, food coloring, fast foods, bread and dairy products.
Propylene glycol is also used in injectable medications, like lorazepam, and in some creams and ointments that are applied to the skin, such as corticosteroids.
Due to Propylene glycols chemical properties, it is also found in a wide variety of hygiene and cosmetic products.
Propylene glycol or 1,2-dihydroxypropane or 1,2-propanediol, is a clear, colourless, viscous, practically odourless liquid with a density of 1.038 g/cm³ at 20°C and a molecular weight of 76.095.
Propylene glycol is miscible with water, acetone and chloroform.
Propylene glycol is miscible in water.
Use in medicinal products
Propylene glycol is a well-known pharmaceutical excipient that is used for several purposes in a wide range of pharmaceutical dosage forms e.g. as a humectant in topicals (15%), as a preservative in solutions (15–30%) or as a co-solvent in aerosols (10–25%), parenterals (10–60%), oral solutions (10–25%) and topicals (5–80%).
Propylene glycol is also used as plasticiser in aqueous film-coating formulations.
Propylene glycol is a high-purity material, having a wide range of practical applications.
PGI is a colorless, water soluble, medium viscosity, hygroscopic liquid with a low vapor pressure and low toxicity.
Propylene glycol is widely employed as a solvent, heat transfer medium or chemical intermediate in numerous industries.
Unsaturated Polyester Resins (UPR)
Unsaturated Polyester Resins (UPR)
Raw material provides good strength
Solvent and grease resistance
Low freeze point
Raw material for alkyd resins
These values are not intended for use in preparing specifications.
Chemical formula: C3H8O2
Molar mass: 76.095 g·mol−1
Appearance : colourless liquid
Density: 1.036 g/cm3
Melting point: −59 °C (−74 °F; 214 K)
Boiling point: 188.2 °C (370.8 °F; 461.3 K)
Solubility in water: Miscible
Solubility in ethanol: Miscible
Solubility in diethyl ether: Miscible
Solubility in acetone: Miscible
Solubility in chloroform: Miscible
log P: -1.34
Thermal conductivity: 0.34 W/m-K (50% H2O @ 90 °C (194 °F))
Viscosity: 0.042 Pa·s
Propylene glycol, also called 1,2-propanediol, resembles ethylene glycol in its physical properties.
Unlike ethylene glycol, however, propylene glycol is not toxic and is used extensively in foods, cosmetics, and oral hygiene products as a solvent, preservative, and moisture-retaining agent.
Propylene glycol is manufactured in large amounts from propylene oxide, which is obtained from propylene.
What is Propylene glycol?
Propylene glycol is an alcohol that absorbs water and mixes completely with many solvents.
While you might see propylene glycol described as an organic compound, this does not mean it’s naturally occurring.
Rather the term organic compound refers to the fact that it contains carbon.
While Propylene glycol’s a liquid, propylene glycol can become vapor in the air when it is heated or shaken vigorously.
Propylene glycol is generally considered safe and non-toxic by the US Food and Drug Administration.
Propylene glycol can be created in two different ways.
Propylene glycol is primarily made by treating propylene oxide—a chemical produced from refining petroleum—with water.
Propylene glycol can also be obtained from glycerol, a major byproduct of the biodiesel production process.
This kind of propylene glycol is mainly used for industrial purposes like making plastic or antifreeze.
Propylene glycol is a dihydric alcohol, a colorless, odorless, slightly viscous liquid with several excellent features as a solvent.
Because of its damping action, moisturizing action, preservation action and emulsifying action, it is used in various applications.
This is a dihydric alcohol, a colorless, odourless, slightly viscous liquid with several excellent features as a solvent.
Propylene glycol is completely soluble in water and it has the feature of dissolving many organic compounds such as fragrances, essential oils and resins and in addition, it has extremely low toxicity and is virtually harmless to the human body.
Moreover, because its boiling point is far higher than that of water, and its freezing point lower, it is also employed as antifreeze or refrigerant, etc., as a heat transfer medium.
General name: propylene glycol
Chemical formula: C3H8O2
Propylene glycol is used in a variety of products and manufacturing processes.
Apart from being used as an intermediary raw material for resins, it has excellent properties as a solvent, and because of features such as its damping action, moisturizing action, preservation action, emulsifying action, high boiling point and low freezing point, it is also used widely in food products, pharmaceuticals, cosmetics, heating mediums, refrigerants and antifreeze.
Propylene glycol is widely used as a solvent in drug manufacturing.
This means that it’s used to dissolve other substances (usually solid) without changing their fundamental structure or composition.
Propylene glycol is commonly used as an excipient in a variety of drugs and it is also authorised in food products and cosmetics.
In addition Propylene glycol has a wide range of other practical applications e.g. used as antifreeze, dicing solution, and as an additive to latex paints and coatings to improve freeze-thaw capability.
Propylene glycol is also used in the generation of artificial mists and fogs used in fire safety training and theatrical and stage productions.
Propylene glycol is also used as a carrier in drug formulations.
Active ingredients can be formulated in it and delivered to the body through it.
Finally, Propylene glycol is used to dilute and stabilize medicines.
Propylene glycol can be used in different forms of drugs including oral drugs like capsules and tablets, topical drugs like creams and gels, and intravenous (injected) drugs.
Inactive Ingredients in Common Pain Medications
Propylene glycol is a commonly found ingredient in cosmetic, personal, and skin care products.
Propylene glycol is in anywhere from 26.4% to 37.8% of registered personal care products.
Propylene glycol is a versatile substance and carries out many functions in the product formulations its included in.
Some of these functions are:
Humectant: Humectants are included in cosmetic and skin care products for their moisturizing abilities.
Propylene glycol works as a humectant by attracting moisture to the skin, and consequently hydrating and moisturizing it.
Solvent: Propylene glycol is used to dissolve substances in a product formulation to get them to mix and work together properly.
Propylene glycol also acts as the carrier for active ingredients.
Emollient: Emollients are ingredients that soothe and hydrate the skin.
They’re very useful in skin care products for treating dry skin.
Propylene glycol is used as an emollient because it forms an oily layer on the skin, and prevents water loss.
Viscosity control: Propylene glycol is used to reduce the thickness of cosmetic formulations and products.
This helps them spread across the skin better, and it also improves how well the products are absorbed.
Preservative: Porpelyne glycol is often used in combination with other chemicals as a preservative in cosmetic and skin care products.
The use of propylene glycol in foods is common and generally considered to be safe.
When consumed, propylene glycol breaks down in the body quite quickly —within 48 hours—and is changed to a source of energy.
Unlike similar substances like ethylene glycol, propylene glycol does not form harmful crystals as it’s being broken down in the body.
Amounts of it that are not broken down and metabolized are passed out of the body in urine.
Some of the ways propylene glycol is used in food include:
As an anticaking agent, helping to prevent lumps from forming in food
As a solvent in food flavorings, helping to dissolve and mix ingredients in them.
As a dough strengthener
To improve flavors in food
As a preservative, its antimicrobial properties help to kill and/or prevent the growth of microorganisms like bacteria and mold
A s a food thickener
To help retain moisture in food
Propylene glycol is safe for consumption and the FDA approves its use in food at certain concentrations.
It may form up to 97% of the contents of seasonings and flavorings, 24% of confections and frosting, and 5% of alcoholic beverages and nuts/nut products
For dairy products and all other food products, the maximum concentrations of propylene glycol are 2.5%, and 2% respectively.
Propylene glycol drops the freezing point of water and water-based liquids, making it effective as an antifreeze.
Propylene glycol makes up a huge part of aircraft deicers, and it's also used to break up ice on runways in airports.
Because propylene glycol is non-toxic, it’s also often used as an antifreeze in food processing systems and in water pipes that lead to connecting hoses.
Alongside vegetable glycerin, propylene glycol is the major ingredient in the liquids (e-liquids) used in e-cigarettes.
To mimic smoke, propylene glycol is converted to extremely tiny droplets by e-cigarettes.
Propylene glycol also functions as a carrier for nicotine and flavorings which are added to some e-liquids.
Recent studies suggest that the use of e-cigarettes might have harmful health effects, and that some of these effects may be linked to the mixture of propylene glycol and other ingredients.
Some of these health risks include lung damage and lung disease.
Other studies also indicate that propylene glycol is converted into cancer-causing compounds when it’s heated up in the e-cigarettes.
Studies on these risks posed by e-cigarettes are still ongoing and the risks are yet to be conclusively defined.
The compound is sometimes called (alpha) α-propylene glycol to distinguish it from the isomer propane-1,3-diol, known as (beta) β-propylene glycol.
Propylene glycol is chiral. Commercial processes typically use the racemate.
The S-isomer is produced by biotechnological routes.
Sources of Exposure
In the general population, propylene glycol exposure occurs primarily through ingestion of food and medications and through skin contact with cosmetics or topical medications.
Propylene glycol is used as a solvent in cosmetics and pharmaceuticals, in various:
Propylene glycol is a diluent found in many intravenous and oral drugs, including:
No adverse health effects are likely to occur from normal use of these products.
However, heavy use of injectable medications with propylene glycol has caused excess levels of propylene glycol in the body.
Prolonged and extensive topical application on compromised skin, such as burns, has also caused excess propylene glycol levels
Propylene glycol is a light, transparent liquid, almost odorless and with low volatility.
Propylene glycol is completely soluble in water and in most organic solvents.
In addition, all propylene glycols have a great capacity to hold and dissolve active ingredients equally which allows them to serve as carriers of aromas, flavours, dyes and moisture.
Propylene glycols, thanks to their excellent properties and quality, are present in areas as varied as personal care, cosmetics, food and pharmaceuticals.
Propylene glycols use must follow strict specifications for quality as laid out in the USP- United States Pharmacopeia and EP-European Pharmacopoeia.
Industrially, propylene glycol is mainly produced from propylene oxide (for food-grade use).
According to a 2018 source, 2.16 M tonnes are produced annually.
Manufacturers use either non-catalytic high-temperature process at 200 °C (392 °F) to 220 °C (428 °F), or a catalytic method, which proceeds at 150 °C (302 °F) to 180 °C (356 °F) in the presence of ion exchange resin or a small amount of sulfuric acid or alkali.
1,2-Propandiol Synthesis V1.svg
Final products contain 20% propylene glycol, 1.5% of dipropylene glycol, and small amounts of other polypropylene glycols.
Further purification produces finished industrial grade or USP/JP/EP/BP grade propylene glycol that is typically 99.5% or greater.
Use of USP (US Pharmacopoeia) propylene glycol can reduce the risk of Abbreviated New Drug Application (ANDA) rejection.
Propylene glycol can also be obtained from glycerol, a byproduct from the production of biodiesel.
This starting material is usually reserved for industrial use because of the noticeable odor and taste that accompanies the final product.
S-Propanediol is synthesized via fermentation methods.
Lactic acid and lactaldehyde are common intermediates.
Dihydroxyacetone phosphate, one of the two products of breakdown (glycolysis) of fructose 1,6-bisphosphate, is a precursor to methylglyoxal.
This conversion is the basis of a potential biotechnological route to the commodity chemical 1,2-propanediol.
Three-carbon deoxysugars are also precursor to the 1,2-diol.
Appearance : Liquid
Color: Colorless and transparent liquid
Odor: Little to none
Boiling point: 187.4°C
Flash poinT: 99 °C
Relative density: 1.038g/cm3 (20/20°C)
What are the benefits for you?
A humectant, Propylene glycol attracts and carries water-based ingredients to the skin and hair.
Propylene glycol softens the hair and allows it to be combed through easily.
In combination with vegetable oils such as olive and almond, it helps to add moisture, increase tensile strength and protect the hair.
Propylene glycol is a petroleum oil-derived compound that has many different uses in the commercial industries.
Propylene glycol is odourless and has no taste description.
Propylene glycol is used in the food, cosmetic, pharmaceutical and plastic industries.
Propylene glycol is also commonly used to create the artificial smoke or mist often seen in discotheques, theatre and television productions.
Reported tobacco industry uses
Propylene glycol is reportedly used as a ‘humectant’ in cigarettes i.e. a substance that traps water to keep the tobacco moist, thus preventing the cigarette from drying out.
Propylene glycol is applied to either the filter or the tobacco and makes up to 2.4% of the total weight of the tobacco used in one cigarette (for cigarettes produced and sold in the EU). In the Netherlands, the average amount added is reported to be 1.3% of the total weight of tobacco in a cigarette, with a maximum of 5.0%.
What is propylene glycol?
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.
Propylene glycol is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products.
Propylene glycol 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.
Propylene glycol 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.
How can propylene glycol ether enter and leave my body?
Propylene glycol can enter your bloodstream if you breathe air containing mists or vapors from this compound.
Propylene glycol can also enter your bloodstream through your skin if you come in direct contact with it and do not wash it off.
If you eat products that contain propylene glycol, it may enter your bloodstream.
Exposure of the general population to propylene glycol is likely since many foods, drugs, and cosmetics contain it.
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.
Safety in humans
When used in average quantities, propylene glycol has no measurable effect on development and/or reproduction on animals and probably does not adversely affect human development or reproduction.
The safety of electronic cigarettes—which utilize propylene glycol-based preparations of nicotine or THC and other cannabinoids—is the subject of much controversy.
Vitamin E acetate has also been identified in this controversy.
The acute oral toxicity of propylene glycol is very low, and large quantities are required to cause perceptible health effects in humans; in fact, the toxicity of propylene glycol is one third of ethanol's.
Propylene glycol is metabolized in the human body into pyruvic acid (a normal part of the glucose-metabolism process, readily converted to energy), acetic acid (handled by ethanol-metabolism), lactic acid (a normal acid generally abundant during digestion) and propionaldehyde (a potentially hazardous substance).
According to the Dow Chemical Company, The LD50 (Lethal Dose that kills 50% of the test population) for rats is 20 g/kg (oral/rat).
Toxicity generally occurs at plasma concentrations over 4 g/L, which requires extremely high intake over a relatively short period of time, or when used as a vehicle for drugs or vitamins given intravenously or orally in large bolus doses.
Propylene glycol would be nearly impossible to reach toxic levels by consuming foods or supplements, which contain at most 1 g/kg of PG, except for alcoholic beverages in the US which are allowed 5 percent = 50 g/kg.
Cases of propylene glycol poisoning are usually related to either inappropriate intravenous administration or accidental ingestion of large quantities by children.
The potential for long-term oral toxicity is also low.
In an NTP continuous breeding study, no effects on fertility were observed in male or female mice that received propylene glycol in drinking water at doses up to 10100 mg/kg bw/day.
No effects on fertility were seen in either the first or second generation of treated mice.
In a 2-year study, 12 rats were provided with feed containing as much as 5% propylene glycol, and showed no apparent ill effects.
Because of its low chronic oral toxicity, propylene glycol was classified by the U. S. Food and Drug Administration as "generally recognized as safe" (GRAS) for use as a direct food additive, including frozen foods such as ice cream and frozen desserts.
The GRAS designation is specific to its use in food, and does not apply to other uses.
Physical State : Liquid
Solubility : Soluble in acetone, chloroform, and ether.
Storage : Store at room temperature
Melting Point : -59° C
Boiling Point : 187.40° C
Density : 1.04 g/mL at 25° C (lit.)
Where is propylene glycol found?
Propylene glycol is used as a softening agent, preservative, humectants, and solvent in cosmetics, fragrances, topical medications, soaps and cleansers, hair care products, and deodorants.
Propylene glycol is also found in oral treatments as well as many foods.
Propylene glycol is also added during the manufacture of many industrial fluids, such as solvents, thinners, antifreeze, other de-icing fluids, desiccants, brake fluids, and polyester resins.
How can you avoid contact with propylene glycol?
Avoid products that list any of the following names in the ingredients:
• Propylene glycol
• EINECS 200-338-0
• EPA Pesticide Chemical Code 068603
• Isopropylene glycol
• Methylethyl glycol
What are some products that may contain propylene glycol?
Antiperspirants and Deodorants
Creams and Lotions
Household Cleaners and Detergents
Paints, Stains, Enamels and Sealers
Shave Creams, Gel
Soaps and Cleansers
A clinician's point of view.
Propylene glycol is also found in air fresheners, such as Glade Premium Room Sprays.
Propylene glycol is also in some food colorings, vanilla flavor, ice cream, and eye lubricant drops.
At times it can be added to packaged or processed foods, especially any that are thick liquids, creams, icings, sauces, etc, but in those cases it will listed as an ingredient.
Also, if a food lists "natural flavors", "natural flavoring", "artificial flavor", or "artificial flavoring", the flavoring can contain propylene glycol that would not be separately listed as an ingredient - in foods with these ingredients listed there is no way to find out for certain if the the food contains propylene glycol or not.
Finally, some beers may contain propylene glycol and beers do not have to list it as an ingredient.
Skin, eye and inhalation contact
Propylene glycol is often used in electronic cigarettes.
Propylene glycol is essentially non-irritating to the skin.
Undiluted propylene glycol is minimally irritating to the eye, producing slight transient conjunctivitis; the eye recovers after the exposure is removed.
A 2018 human volunteer study found that 10 male and female subjects undergoing 4 hours exposures to concentrations of up to 442 mg/m3 and 30 minutes exposures to concentrations of up to 871 mg/m3 in combination with moderate exercise did not show pulmonary function deficits, or signs of ocular irritation, with only slight symptoms of respiratory irritation reported.
Inhalation of propylene glycol vapors appears to present no significant hazard in ordinary applications.
Due to the lack of chronic inhalation data, it is recommended that propylene glycol not be used in inhalation applications such as theatrical productions, or antifreeze solutions for emergency eye wash stations.
Recently, propylene glycol (commonly alongside glycerol) has been included as a carrier for nicotine and other additives in e-cigarette liquids, the use of which presents a novel form of exposure.
The potential hazards of chronic inhalation of propylene glycol or the latter substance as a whole are as-yet unknown.
According to a 2010 study, the concentrations of PGEs (counted as the sum of propylene glycol and glycol ethers) in indoor air, particularly bedroom air, has been linked to increased risk of developing numerous respiratory and immune disorders in children, including asthma, hay fever, eczema, and allergies, with increased risk ranging from 50% to 180%.
This concentration has been linked to use of water-based paints and water-based system cleansers.
However, the study authors write that glycol ethers and not propylene glycol are the likely culprit.
Propylene glycol has not caused sensitization or carcinogenicity in laboratory animal studies, nor has it demonstrated genotoxic potential.
Studies with intravenously administered propylene glycol have resulted in LD50 values in rats and rabbits of 7 mL/kg BW.
Ruddick (1972) also summarized intramuscular LD50 data for rat as 13-20 mL/kg BW, and 6 mL/kg BW for the rabbit.
Adverse effects to intravenous administration of drugs that use propylene glycol as an excipient have been seen in a number of people, particularly with large bolus dosages.
Responses may include CNS depression, "hypotension, bradycardia, QRS and T abnormalities on the ECG, arrhythmia, cardiac arrhythmias, seizures, agitation, serum hyperosmolality, lactic acidosis, and haemolysis".
A high percentage (12% to 42%) of directly-injected propylene glycol is eliminated or secreted in urine unaltered depending on dosage, with the remainder appearing in its glucuronide-form.
The speed of renal filtration decreases as dosage increases, which may be due to propylene glycol's mild anesthetic / CNS-depressant -properties as an alcohol.
In one case, intravenous administration of propylene glycol-suspended nitroglycerin to an elderly man may have induced coma and acidosis.
However, no confirmed lethality from propylene glycol was reported.
Propylene glycol is an approved food additive for dog and sugar glider food under the category of animal feed and is generally recognized as safe for dogs, with an LD50 of 9 mL/kg.
The LD50 is higher for most laboratory animals (20 mL/kg).
However, Propylene glycol is prohibited for use in food for cats due to links to Heinz body formation and a reduced lifespan of red blood cells.
Heinz body formation from MPG has not been observed in dogs, cattle, or humans.
PG has been used in the dairy industry since the 1950s for cows showing signs of ketosis.
The negative energy balance during the early stages of lactation can cause the animal's body to have lower glucose levels, inducing the liver to make up for this by the conversion of body fat, leading to several health conditions, e.g. displaced abomasum.
PG "reduces the propionate ratio of acetate to acetaminophen, while increasing conversion of ruminal PG to propionate, and aid[s] in the closure of energy deficit in cattle."
Estimates on the prevalence of propylene glycol allergy range from 0.8% (10% propylene glycol in aqueous solution) to 3.5% (30% propylene glycol in aqueous solution).
The North American Contact Dermatitis Group (NACDG) data from 1996 to 2006 showed that the most common site for propylene glycol contact dermatitis was the face (25.9%), followed by a generalized or scattered pattern (23.7%).
Investigators believe that the incidence of allergic contact dermatitis to propylene glycol may be greater than 2% in patients with eczema or fungal infections, which are very common in countries with lesser sun exposure and lower-than-normal vitamin D balances.
Therefore, propylene glycol allergy is more common in those countries.
Because of its potential for allergic reactions and frequent use across a variety of topical and systemic products, propylene glycol was named the American Contact Dermatitis Society's Allergen of the Year for 2018.
Recent publication from The Mayo Clinic reported 0.85% incidence of positive patch tests to propylene glycol (100/11,738 patients) with an overall irritant rate of 0.35% (41/11,738 patients) during a 20-year period of 1997–2016.
87% of the reactions were classified as weak and 9% as strong.
The positive reaction rates were 0%, 0.26%, and 1.86% for 5%, 10%, and 20% propylene glycol respectively, increasing with each concentration increase.
The irritant reaction rates were 0.95%, 0.24%, and 0.5% for 5%, 10%, and 20% propylene glycol, respectively.
Propylene glycol skin sensitization occurred in patients sensitive to a number of other concomitant positive allergens, most common of which were: Myroxylon pereirae resin, benzalkonium chloride, carba mix, potassium dichromate, neomycin sulfate; for positive propylene glycol reactions, the overall median of 5 and mean of 5.6 concomitant positive allergens was reported.
Propylene glycol occurs naturally, probably as the result of anaerobic catabolism of sugars in the human gut.
Propylene glycol is degraded by vitamin B12-dependent enzymes, which convert it to propionaldehyde.
Propylene glycol is expected to degrade rapidly in water from biological processes, but is not expected to be significantly influenced by hydrolysis, oxidation, volatilization, bioconcentration, or adsorption to sediment.
Propylene glycol is readily biodegradable under aerobic conditions in freshwater, in seawater and in soil.
Therefore, propylene glycol is considered as not persistent in the environment.
Propylene glycol exhibits a low degree of toxicity toward aquatic organisms.
Several guideline studies available for freshwater fish with the lowest observed effect concentration of 96-h LC50 value of 40,613 mg/l in a study with Oncorhynchus mykiss.
Similarly, the effect concentration determined in marine fish is a 96-h LC50 of >10,000 mg/l in Scophthalmus maximus.
Although propylene glycol has low toxicity, it exerts high levels of biochemical oxygen demand (BOD) during degradation in surface waters.
This process can adversely affect aquatic life by consuming oxygen needed by aquatic organisms for survival.
Large quantities of dissolved oxygen (DO) in the water column are consumed when microbial populations decompose propylene glycol.
Preferred IUPAC name
Propylene glycol is a clear, colorless, viscous liquid with a faintly sweet taste.
Propylene glycol and ethylene glycol have similar physical properties and uses.
Their chemical structures differ by only one methyl group (ethylene glycol = HOCH2CH2OH; propylene glycol = CH3CH[OH]CH2OH).
Ethylene glycol is a potent cause of acute toxicity in humans.
In contrast, propylene glycol is a “generally recognized as safe” additive for foods and medications.
Most reported cases of propylene glycol toxicity have resulted from propylene glycol used as a diluent for intravenous administration of benzodiazepines.
Methyl ethyl glycol
Propylene Glycol USP
Solar Winter BAN
Propylene Glycol Description
Propylene glycol is a humectant (hydrator) that can enhance the delivery of key active ingredients into skin.
Propylene glycol also plays a role in keeping formulas from melting in high heat or from freezing in low temps.
Also known as 1,2-propanediol, propylene glycol is used in thousands of personal care products with a proven track record of safety.
As a raw material, Propylene glycol is a clear, purified liquid that is produced synthetically.
There are some websites that state propylene glycol is really industrial antifreeze and that it is a strong skin sensitizer.
They further point out that the Material Safety Data Sheet (MSDS) on propylene glycol warns users to avoid skin contact.
As ominous as this sounds, Propylene glycol’s far from the reality of how propylene glycol is used in cosmetics formulations.
The Cosmetic Ingredient Review Board and other groups have analyzed the toxicology data and exposure studies concerning topical application of propylene glycol as commonly used in cosmetics.
Their conclusion was that it is safe and does not pose a health risk to consumers.
Concentrations of up to 73% have been reported with leave-on products; for rinse-off products, higher concentrations are permissible.
What is Propylene glycol?
Propylene glycol (CH8O2) is a commonly used drug solubilizer in topical, oral, and injectable medications.
Propylene glycol is used as stabilizer for vitamins, and as a water-miscible cosolvent.
Propylene glycol has been used for over 50 years in a large variety of applications.
As a pharmaceutical additive, propylene glycol is generally regarded as safe.
However, in the pediatric population, propylene glycol has been implicated in toxicity.
Cases of hyperosmolality from absorption of creams applied to burns have been reported.
Contact dermatitis has also occurred with topical application in the pediatric population.
Hemolysis, central nervous system depression, hyperosmolality, and lactic acidosis have been reported after intravenous administration.
Propylene glycol is metabolized to lactic acid, which may lead to the reported lactic acidosis.
The high concentration of propylene glycol contained in certain intravenous drug products, such as phenytoin, diazepam, digoxin, and etomidate, may induce thrombophlebitis.
Rapid infusion of solutions containing high concentrations of propylene glycol-containing drugs has been linked to respiratory depression, arrhythmias, hypotension, and seizures.
Seizures and respiratory depression have also occurred in children who have ingested oral solutions containing propylene glycol.
Propylene glycol is also used as moisturizer in cosmetic products and as a dispersant in fragrances.
There are many other food and industrial uses for propylene glycol.
As a food additive, propylene glycol is on the U.S. Food and Drug Administration (FDA) generally regarded as safe list (not to be confused with ethylene glycol, which is extremely toxic if ingested).
According the FDA, as a food additive, propylene glycol is metabolized in the body and is used as a normal carbohydrate source.
Long-term use and substantial quantities of propylene glycol (up to five percent of the total food intake) can be consumed without causing toxicity.
There is no evidence in the available information on propylene glycol that demonstrates, or suggests a hazard to the public when they are used at levels that are now current or might reasonably be expected in the future.
Sentry Propylene Glycol
FEMA No. 2940
Caswell No. 713
SDM No. 27
EPA Pesticide Chemical Code 068603
1,2-(RS)-Propanediol; 1,2-Dihydroxypropane; 1,2-Propylene glycol
Propylene Glycol (Propane-1,2-diol)
All purpose lubricant
Propylene glycol [USP:JAN]
Propylene glycol, USP
Average MW 1000
Propylene glycol (TN)
racemic propylene glycol
Propylene glycol dl-form
Propylene Glycol 50/50
propylene glycol cefatrizine
Propylene glycol, FCC, FG
Polypropylene glycol 1,000
3-01-00-02142 (Beilstein Handbook Reference)
Propylene Glycol Reagent Grade
Propylene glycol (JP17/USP)
1,2-Propanediol, ACS reagent
Glycol, polypropylene (P400)
Glycol, polypropylene (P750)
Glycol, polypropylene (P1200)
Propylene Glycol (Fragrance Grade)
Propylene Glycol, Industrial Grade
1,2-Propanediol, LR, >=99%
1,2-Propanediol, USP, 99.5%
1,2-Propanediol, analytical standard
1,2-Propanediol, puriss., 99.5%
Poly(propylene glycol) average Mw 400
Poly(propylene glycol) average Mw 1000
Poly(propylene glycol) average Mw 2000
Poly(propylene glycol) average Mw 3000
1,2-Propanediol, ReagentPlus(R), 99%
1,2-Propanediol, ACS reagent, >=99.5%
1,2-Propanediol, ReagentPlus(R), >=99%
1,2-Propanediol, analytical reference material
1,2-Propanediol, tested according to Ph.Eur.
1,2-Propanediol 100 microg/mL in Acetonitrile
1,2-Propanediol, p.a., ACS reagent, 99.5%
1,2-Propanediol, SAJ first grade, >=99.0%
1,2-Propanediol, SAJ special grade, >=99.0%
1,2-Propanediol, Vetec(TM) reagent grade, 98%
Propylene Glycol, meets USP testing specifications
1,2-Propanediol, puriss. p.a., ACS reagent, >=99.5% (GC)
Propylene glycol, British Pharmacopoeia (BP) Reference Standard
Propylene glycol, European Pharmacopoeia (EP) Reference Standard
Propylene glycol, United States Pharmacopeia (USP) Reference Standard
1,2-Propanediol, meets analytical specification of Ph. Eur., BP, USP, >=99.5%
Propylene glycol, Pharmaceutical Secondary Standard; Certified Reference Material
Soybean oil,polymer with benzoic acid,pentaerythritol,phthalic anhydride and propylene glycol