Propylene Glycol


Mono Propylene Glycol

What is propylene glycol?

Propylene glycol is a colourless organic liquid. The chemical name is "Propane-1,2-diol" with formula C3H802. The CAS registry number is 57-55-6. Typical names are propylene glycol (PG) and monopropylene glycol (MPG). The propylene glycol can be manufactured in different grades. The most controlled grade is called propylene glycol-USP/EP and is manufactured and distributed according to high industry standards. The normal PG grade is called industrial grade. Both grades may be marketed under different trade names.

A web search for propylene glycol can be performed in several other languages :

French : Propylène glycol
German : Propylenglykol
Dutch: Propyleenglycol
Portuguese : Propilenoglicol
Spanish: Propilenglicol o glicoles propilénicos
Italian: Glicole propilenico
Bulgarian: Пропиленгликола
Russian: Пропиленглико́ль



Which products contain propylene glycol?

Propylene glycol is used in a large variety of every day convenience and care products, such as in cosmetics and toiletries, food, animal feed, and pharmaceuticals, as well as in a number of industrial applications.

How can I know that propylene glycol is in a product: Is it labelled?

When propylene glycol USP/EP (pharmaceutical grade) is used in food, you will find it labelled as "E 1520". Used in animal feed is not labelled, propylene glycol is an authorized feed material. In cosmetics there is no requirement for an "E"-number, you will find propylene glycol listed as such in the ingredient list. In industrial products, there is no requirement for propylene glycol to be labelled.

How can I come in contact with propylene glycol?

Most consumers will get in contact with propylene glycol during their normal everyday life, when consuming personal care articles like creams, sprays, lotions, when enjoying soft drinks, sweets and other foods, or when taking a medicine or being vaccinated against a severe disease.

What happens with propylene glycol in the body?

Propylene Glycol is expected to be readily absorbed by oral exposure whereas uptake through the skin is very low. Once in the body, under conditions of normal low exposure, propylene glycol is quickly metabolised and excreted. The half-life of propylene glycol in the blood stream is about 2-4 hours. It is primarily metabolised to lactate which is further metabolised to pyruvate, carbon dioxide and water. Lactate also contributes to glucose formation through gluconeogenic pathways. Very large exposures to propylene glycol may result in lactic acidosis and hyperosmotic changes in the blood.

Is there any maximum safety level for ingestion?

Propylene glycol is used professionally by manufacturers of consumer and industrial products, but it is not available to consumers as pure substance. Under normal conditions it is therefore impossible to ingest propylene glycol in large amounts, and consumer exposure to propylene glycol via products is extremely low. In addition, studies have shown that propylene glycol has a very low degree of toxicity.

Actually, from a toxicological point of view, alcohol is more toxic than propylene glycol. European legislation limits the presence of propylene glycol as food additive to 1-3 g/kg in the final foodstuff (0.1-0.3%). A full acceptable daily intake (ADI) of 0 – 25 mg/kg bodyweight has been assigned for propylene glycol by the European Commission´s Scientific Committee on Food.

Can propylene glycol have negative health effects when consuming it over a long period/time in small amounts?

Propylene glycol has been used safely for more than 50 years in a large variety of applications. Studies have shown that propylene glycol has a very low degree of toxicity. No negative health effects from exposure to small amounts of propylene glycol have ever been observed. The authorities have approved the use of propylene glycol in sensitive applications such as in pharmaceuticals, food and cosmetics, and thus confirm its safety.

Is the safety of propylene glycol regularly re-assessed?

The companies producing and using propylene glycol apply rigorous standards to ensure the highest level of quality and hygiene, and they regularly control their processes. In addition, the European Chemical Industry Council and the European Federation of Chemical Distributors have initiated a uniform assessment system throughout the whole value chain. Under this scheme, independent auditors regularly assess authorised partners on the basis of an agreed set of quality criteria.

Is the use of propylene glycol in electronic cigarettes safe?

The producers of propylene glycol and members of Cefic's PO/PG sector group do not support the use of propylene glycol in electronic cigarettes, nor in artificial (theatrical) fogs due to possible effects on the eye, nose, throat, and respiratory tract membranes as well as the absence of information on potential long term effects from prolonged inhalation of (fine) droplets of propylene glycol.

Who controls the safety of propylene glycol in Europe?

The European Council´s Pharmacopoeia document issued by the European Directorate for the Quality of Medicines (EDQM) defines strict rules for the identification, analytical testing and quality specifications of chemicals used in pharmaceutical applications, such as propylene glycol. This document is regularly updated, recently in 2008. In addition, the European authorities responsible for consumer safety have assessed propylene glycol USP/EP (pharmaceutical grade) and approved it to be safe for use in direct and indirect food contact. For cosmetics applications, it is the Personal Care Products Council that monitors and approves the use of substances in cosmetics, such as propylene glycol USP/EP.

Can I be sure that industrial propylene glycol will not be used for pharmaceutical applications?

In fact, the quality and purity of both industrial propylene glycol and propylene glycol USP/EP (pharmaceutical grade) is very high. In addition, for propylene glycol USP/EP intended for use in pharmaceutical applications, utmost care is placed on fulfilling the specific strict rules for the production, transport and hygiene of propylene glycol USP/EP to be used in sensitive applications like in food or cosmetics. All members of the Cefic Propylene Oxide / Propylene Glycol business group do not support the use of industrial propylene glycol for use in pharma, food, animal feed and cosmetic/personal care applications.

How can a de-icer be used in food or in cosmetics?

It is not the "de-icer" that is used; the different "natural" functionalities of propylene glycol make it the preferred substance in both applications. In the de-icer it is the ability to reduce the freezing point, in cosmetics the ability to dissolve, emulsify, or carry active ingredients in substances. In the de-icer industrial propylene glycol is used, in the cosmetic it is of course propylene glycol USP/EP (pharmaceutical grade). It is the multifunctionality of propylene glycol that offers this wide variety of uses.

How pure is pharmaceutical propylene glycol?

Propylene glycol USP/EP (pharmaceutical grade) has a very high purity (i.e. absence of impurities) of more than 99,5% – which is extremely high for a chemical. Most important, though, is respecting hygiene regulations and Good Manufacturing Practice standards in the production, transport and further processing of propylene glycol.

How is the seamless distribution chain controlled?

The companies producing and using propylene glycol apply rigorous standards to ensure the highest level of quality and hygiene. The companies organised in Cefic have committed themselves to acting under the voluntary industry initiative "Responsible Care", where they work together to continuously improve their health, safety and environmental performance. In addition, the European Chemical Industry Council and the European Federation of Chemical Distributors have initiated a uniform assessment system throughout the whole distribution chain. Under this scheme, independent auditors regularly assess authorised partners on the basis of an agreed set of criteria for food, pharma and cosmetic type products, including propylene glycol USP/EP (pharmaceutical grade).

Is propylene glycol safe for human health? Can it for example give me a migraine, cause erythema or other allergic reactions?

There might be very individual personal conditions in a body that result in a highly sensitive reaction to any kind of chemical substance. However, propylene glycol USP/EP (pharmaceutical grade) has been safely used for decades in a large variety of consumer products, including more than 4000 cosmetics and toiletry products. Over this long period of time and large of variety of products there has been no evidence of such effects.

Is propylene glycol used in pet food safe for all animals?

Propylene glycol is an approved feed material. However, whilst it is safe for use in cattle, dogs and poultry it shall not be used in cat feed. When fed with propylene glycol containing feed, cats show an increase in Heinz body formation, which are deformities of erythrocytes and shorten the life time of the red blood cells. This is unique to cats. Read more about it.

Is propylene glycol one of the „softeners“ in everyday products which are under discussion regarding alleged carcinogenic effects?

No, propylene glycol USP/EP (pharmaceutical grade) is used as emulsifier, solvent, carrier of flavours, thickener, clarifier or stabiliser, not as softener. In addition, animal-studies have shown that propylene glycol does not have carcinogenic effects.

Is propylene glycol safe for babies and small children?

From over 50 years of safe use, and from existing studies, there is no indication that propylene glycol has any negative effects on the health of humans, including that of babies and small children.

Is mono-propylene glycol registered under the REACH legislation?

Yes. The molecule propane-1,2-diol (CAS 57-55-6) is registered under n° 01-2119456809-23.

Is propylene glycol authorised as feed material?

As of October 2010 propylene glycol is an approved animal feed material according to EU Regulation 892/2010. It is listed in the Catalogue of Approved Feed Materials (EU Regulation 68/2013, no. 13.11.1) and in the Register of Feed Materials. Prior to October 2010, propylene glycol was only approved as feed additive.

Is Propylene Glycol Classified as Hazardous?

Propylene glycol is not classified as hazardous according to the Regulation (EC) No 1272/2008 (CLP Regulation) Annex VI.  Propylene glycol was the subject of a proposal l for Harmonized Classification and Labelling  that was submitted in 2015 to the European Chemicals Agency (ECHA) by the German Federal Institute for Occupational Safety and Health (BAuA).
The Risk Assessment Committee (RAC) of ECHA decided by consensus at its meeting on December 9th 2016 that propylene glycol does not warrant classification as STOT SE 3 (H335, may cause respiratory irritation). The decision adopts the results of a 2016 study initiated by the European producers of propylene glycol to improve the information on human respiratory irritation. This study on humans tested 4 hour exposures to up to 100 mg/m3 and 30 minute exposures to 200 mg/mg3 and the results found propylene glycol not to be a respiratory or ocular irritant. The text of the RAC opinion and the RAC responses to comments received on the proposed classification is available on the ECHA website

Is Propylene Glycol A Skin Sensitizer?

Propylene Glycol is a Generally Recognized As Safe (GRAS) substance that is used in a broad range of consumer applications, including in pharmaceutical topical and cosmetic preparations. It has been extensively tested in animals and human volunteers and none of these tests have been indicative of skin allergies. However, in clinical diagnostic studies, skin reactions suggestive of allergic contact dermatitis, irritant contact dermatitis, nonimmune contact urticaria, or subjective irritation have been occasionally reported for Propylene Glycol[1],[2],[3]. A recent study by Mayo Clinic and Brown University investigators[4] with a total of 11,738 patients reported that 0.85% had been deemed positive whereas 0.35% had irritant reactions to Propylene Glycol. It should be reiterated that the interpretation of such diagnostic patch testing is complicated, subjective, requires scoring experience and repeated testing to distinguish between a slight irritant vs. allergic skin reaction in affected individuals. Furthermore, this study also reported that 44% of patients with allergic reactions to Propylene Glycol had known histories of skin atopy, had multiple other allergies, and the majority of diagnostic skin reactions were weak (87%). The affected individuals reacted to a mean of 5.6 concomitant additional allergens, including a very common Balsam of Peru allergen which was most frequently co-diagnosed with Propylene Glycol. The authors also stated that some concomitant allergens may have a role as co-sensitizers with Propylene Glycol in these individuals. Overall, the risk of developing skin sensitization to Propylene Glycol on uncompromised skin of individuals with healthy immune function appears to be very low.

[1] Lessmann H, Schnuch A, Geier J, Uter W. (2005). Skin-sensitizing and irritant properties of propylene glycol.

Contact Dermatitis, 53(5), 247-259.

[2] Warshaw EM, Botto NG, Maibach HI, Fowler Jr. JF, Rietschel RL, Zug KA, Belsito DV, Taylor JS, DeLeo VA,

Pratt MD, Sasseville D, Storrs F, Marks Jr. JG, Mathias CGT. (2009). Positive patch-test reaction to propylene

glycol: a retrospective cross-sectional analysis from the North American Contact Dermatitis Group, 1996 to 2006.

Dermatitis, 20(1), 14-20.

[3] Funk JO, Maibach HI. (1994). Propylene glycol dermatitis: re-evaluation of an old problem. Contact Dermatitis, 31(4), 236-241.

[4] Lalla SC, Nguyen H, Chaudhry H, Killian JM, Drage LA, Davis MDP, Yiannias JA, Hall MR. (2018). Patch Testing to Propylene Glycol: The Mayo Clinic Experience. Dermatitis, 29(4), 200-205.

Why has Propylene Glycol been named 2018 “Allergen of the Year”?

Based on toxicological safety testing outcomes, Propylene Glycol is not a skin allergen in animals and human volunteers. However, rare instances of contact dermatitis have been reported in certain individuals using topical preparations containing Propylene Glycol. Hence, the 2018 “Allergen of the Year” label has been inappropriately applied to Propylene Glycol. Individuals with healthy skin and immune function have low risk of developing allergies to this non-hazardous substance. Recent studies indeed show that Propylene Glycol allergies develop as a result of a number of driving factors, such as compromised skin barrier and pre-existing allergies (these patients are allergic to several other substances in addition to Propylene Glycol). Therefore, on its own Propylene Glycol is unlikely to cause skin allergies and this Generally Recognized As Safe (GRAS) substance should not be equated with other confirmed skin sensitizers.

Di Propylene Glycols

Which products contain Di Propylene Glycol?

Personal care products such as deodorants, fragrances and perfumes, facial make-ups, soaps, shaving and skin care formulations, may contain DPG. Furthermore, DPG can be used as a raw material in the manufacture of polyester resins and of benzoate plasticizers. However, the DPG is converted to such products and it is essentially not present as DPG.

Can Di Propylene Glycol have adverse health effects?

Under conditions of normal use, DPG is a low concern for adverse health effects. DPG has low acute toxicity by oral, dermal and inhalation routes of exposure, although transient signs of altered nervous system function (commonly observed with short-chain glycol exposure) may occur following oral exposure to high levels. It is not irritating to the eyes or skin and does not cause allergic skin reactions. DPG is not a concern for repeated exposure toxicity at relevant exposure levels and is not considered to be carcinogenic or genotoxic, nor does it have effects on fertility or reproduction. 

Can DPG be harmful in the environment?

Under conditions of normal use, DPG is a low concern for adverse environmental effects. In the environment, DPG is readily biodegradable, is not expected to bio-accumulate and is of very low toxicity to aquatic organisms.

Is the use of DPG regulated?

Please refer to the section on Regulatory and Science.

What happens with DPG in the body?

DPG is expected to be readily absorbed by oral exposure but exposures through the skin are likely negligible and inhalation exposure to significant quantities of DPG is not expected.  Studies on the metabolism of structurally similar propylene glycols indicate that in the body DPG will readily break down to propylene glycol and then to carbon dioxide.