FAQ

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

 

 

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.

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.

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.

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.

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.

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.

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 (Cefic) 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. Finally, various regulatory agencies in Europe periodically review the available information for propylene glycol to assure its safety-in-use for the intended applications; these key agencies are the European Chemicals Agency (ECHA), European Food Safety Authority (EFSA) and European Medicines Agency (EMA). In a partnership between Cefic and ECHA, the companies undertook the REACH Dossier Improvement Action Plan to enhance the quality and the extend of available information for propylene glycol.

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.

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. The USP monograph is regularly updated, recently in 2020. 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. Finally, agencies such as European Food Safety Authority (EFSA) and European Medicines Agency (EMA) periodically review the available safety data on propylene glycol to assure that the safety limits set by them for food and pharmaceutical applications, respectively, are protective to the health of European consumers.

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.

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.

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.

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).

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.

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.

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.

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

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.

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.

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.

To reaffirm the safety-in-use of propylene glycol as a food additive, the European Food Safety Authority (EFSA) has re-evaluated this substance in a program that examines all food additives that were permitted in the European Union prior to January 2009. EFSA completed their review of propylene glycol (E 1520) in March 2018 and their conclusion was to sustain the current acceptable daily intake (ADI) level of 25 mg/kg body weight per day. Their assessment of dietary risk found that the mean and high exposure levels of the refined exposure assessment scenarios (including the brand-loyalty general population scenario related to the repetitive purchases of flavoured drinks did not exceed the ADI in any population group for the use of propylene glycol as a food additive at the reported use. The EFSA opinion is published in the 2018 EFSA journal (EFSA Journal 2018 16(4):5235; www.efsa.europa.eu/efsajournal).

Yes, the companies producing and using propylene glycol are constantly re-evaluating the data needs for this substance as a result of new scientific developments and evolving regulations. To address the reports implying an irritation potential of this substance, a new human study was performed by the European producers to clarify previous reports of eye and respiratory tract irritation potential following brief exposures to high concentrations of propylene glycol mists. The new study was performed at the distinguished Monell Chemical Senses Center in Philadelphia PA, USA using 20 volunteers exposed to propylene glycol aerosols ranging from 20 to 200 mg/m³ (representing a moderate and dense fog environment) for 30 minutes or 4 hours. The subjects were examined for self-reported irritation symptoms and changes in objective measurements for eye and respiratory effects. The study found no exposure-related changes in objective measures of pulmonary function or eye irritation and only slight changes in self-reported respiratory symptom. The results of this study demonstrate that acute exposure to the concentrations of propylene glycol tested does not affect human respiratory function or produce ocular irritation. The study is published in the journal of Inhalation Toxicology (Dalton et al. 2018. Lack of respiratory and ocular effects following acute propylene glycol exposure in healthy humans, Inhalation Toxicology, DOI: 10.1080/08958378.2018.1470207).

Babies can be exposed to high doses of propylene glycol in hospital settings where it is used as a critical excipient for administration of intravenous medicines with low water solubility. While newborns and babies can be at increased risk of temporary health side effects from high bolus doses of propylene glycol excipient, these effects are known and can be mitigated with medical interventions. To assure the safety-in-use of propylene glycol given to this young age group in pharmaceuticals, the European Medicines Agency (EMA) has reviewed the available toxicological and clinical data as well as use information. Consequently, EMA has set new safety limits to propylene glycol (E 1520) and its esters from medicines in 2017 for young children (EMA/CHMP/334655/2013). These safe doses have been set at 1 mg/kg BW/day for children less than 1 month of age, and at 50 mg/kg BW/day for children from 1 month to 5 years of age. The full EMA/CHMP/334655/2013 evaluation can be accessed here.

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.

Various maximum doses have been established for adults exposed to propylene glycol from various applications. For example, as a direct food additive, both WHO and the European Food Safety Authority (EFSA) have adopted the acceptable daily intake (ADI) value of 0-25 mg/kg BW/day. Moreover, the European Medicines Agency (EMA) has recently recommended the safe dose of 500 mg/kg BW/day for use of propylene glycol as a pharmaceutical excipient for children 5 to 17 years as well as adults (EMA/CHMP/334655/2013). Furthermore, EMA has set a new safety limit at 1 mg/kg BW/day for children less than 1 month of age, and at 50 mg/kg BW/day for children from 1 month to 5 years of age. The full EMA/CHMP/334655/2013 evaluation can be accessed here.

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.

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. 

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.

Please refer to the section on Regulatory and Science.

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.