The use of polysorbate in natural cosmetics
Author: Matylda Kupka, Technical University of Lodz
Date of submission: 16.02.2021
1. An overview of polysorbates
Polysorbates are a family of amphipathic, non-ionic surfactants. They are oily substances derived from ethoxylated sorbitan or isosorbide esterified with fatty acids. Polysorbates have many different forms, but they generally differ with respect to the number of polymerized oxyethylene subunits and the number and type of fatty acid moieties present in their structure1. Some of the most commonly used building units of polysorbates are polyethoxylated sorbitan or sorbitol esters of fatty acids. Each ingredient has a common core structure of sorbitan or sorbitol, etherified with PEG chains, and esterified with fatty acids.
There are two possible paths for the synthesis of polysorbates. The first path consists of sorbitol esterification with fatty acids or their anhydrides. This method usually requires the presence of an acid catalyst. The process is typically performed at 130-180˚C. At this temperature, the water is completely eliminated from sorbitol. The remaining molecule may form three possible isomers of sorbitan. If the elimination of another water molecule takes place, then the product may be transformed into isosorbide. The products of sorbitol dehydration react with fatty acid and in result form certain sorbitan esters.
Another method for manufacturing polysorbates is the reaction of sorbitol with ethylene oxide and a basic catalyst at 200- 250°C. Such conditions allow the isomerization of the sorbitol molecule as above. Then, ethylene oxide is added and as a result, ethoxylated products are obtained. Those end products are called carbowaxes and may be esterified with fatty acids to produce oligomers of polysorbates2.
Figure 1. The structures of sorbitan derived polysorbate, sorbitan, sorbitol derived polysorbate, and sorbitol3
Polysorbates are amphiphilic molecules. They are most often present in the form of viscous liquids in the color range from yellow to tanned orange. Their smell may be described as a faint, characteristic odor. The taste of polysorbates is somewhat bitter. The reported generic chemical and physical properties of sorbitan monolaurate, ethoxylated, and sorbitan monostearate, ethoxylated are presented in Table 1 and Table 2 respectively4.
Table 1. Chemical and physical properties of generic sorbitan monolaurate, ethoxylated.
Table 2. Chemical and physical properties of generic sorbitan monostearate, ethoxylated5.
Polysorbates are commonly used in the food and pharmaceutical industry. They can act as protein stabilizers, which help to elongate the shelf life of a drug product. However, they are chemically diverse mixtures, which may degrade through oxidation and hydrolysis. The polysorbate degradation may negatively affect the quality, efficacy, safety, or stability of the protein formulation. Therefore, health authorities are still working on imposing new control strategies to assure the constant content of polysorbates in drugs and medication. Other than that, polysorbates are great emulsifiers and surfactants. They also show water solubility, which makes them safe and friendly for the environment. Due to their surfactant and emulsifying properties, they are often used in the production of natural cosmetics, as they are a safe, non-irritant, eco-friendly alternative to other chemicals.
2. Polysorbate 20
One of the most commonly used variations of polysorbates used in the cosmetic industry is Polysorbate 20 (Polyoxyethylene (20) sorbitan monolaurate). It is a lauric acid with an approximate hydrophilic-lipophilic balance of 16.76. The main components of PS 20 are: sorbitol, fatty acids with an average alkyl chain length of 12 carbon atoms, and ethylene oxide (EO).
Figure 2. The molecular structure of Polysorbate 20 (Polyoxyethylene (20) sorbitan monolaurate)
Polysorbate 20 is a nonionic surfactant and finds use in a variety of cosmetic and personal care products. Due to its oily, liquid, and gentle nature, PS 20 acts as a nonionic surfactant and wetting agent, therefore enhancing the spreadability of liquids. It is also commonly used as a solubilizer, as it enables the attachment of fragrance and essential oils to various types of cosmetic bases. This substance prevents the separation of oils and bases such as cream, liquid, or gel bases. Polysorbate 20 often acts as a dispersant, as it helps to diffuse oils throughout the water and as an anti-static agent that prevents the build-up of static charges. Adding this compound to oil-based cosmetics may also reduce and prevent them from clumping or settling. Moreover, it is used as a thickener and viscosity modifier, as it stops the changes to a product’s viscosity at changing temperatures. It helps products retain both fragrance and clarity7.
Polysorbate 20 is usually added to water-based cosmetics to ensure the blend of essential oils and fragrance oils with the bases to which they are added. As it is non-irritant and soothing, it is often used in bath products, facial cleansers, baby products, and shampoos. Other applications of Polysorbate 20 include face creams, linen sprays, body lotions, balms, ointments, pomades, hair spray, and sunblocks8.
In terms of toxicity or potential hazard concerning Polysorbate 20, no studies have shown major issues so far. Nevertheless, according to the Cayman Chemicals Safety Data Sheet, the material may be irritating to the mucous membranes and upper respiratory tract. The ingestion, inhalation, or skin absorption may also be hazardous if caution is not taken. The main side effects of using Polysorbate 20 include eye, skin, and respiratory system irritation9. However, in most of the studies conducted on humans concerning the irritation of the material, Polysorbate 20 was not dermally irritating10. The toxical properties have not been thoroughly investigated. No carcinogenicity data has been published. The Cosmetics Ingredient Review (CIR) Expert Panel evaluated the data and concluded that Polysorbate 20 is safe as a cosmetic ingredient11.
3. Polysorbate 60
Another type of polysorbate used in the cosmetic industry is Polysorbate 60 ((polyoxyethylene (20) sorbitan monostearate)). It comes in the form of orange, oily, viscous liquid at room temperatures. At lower temperatures, it becomes semisolid. PS 60 has a hydrophilic to lipophilic balance of 14.9. Due to the longer length of stearic acid, it is slightly more lipophilic than Polysorbate 20.
The method of production consists of reacting stearic acid with sorbitol and then ethylene oxide. This technique is called ‘ethoxylation of sorbitan’. Sorbitan is a dehydrated form of sorbitol. In an ethoxylation reaction, ethylene oxide is added to a substrate. Sorbitan reacts with 60 units of EO, hence the name. The final step of the production of Polysorbate 60 is a reaction with fatty acids, which are usually obtained from vegetable fats and oils12.
Figure 3. The structure of Polysorbate 6013
Due to its high hydrophilic to lipophilic balance, it is used to help water and oil-based ingredients to blend, as well as to prevent their separation. The material is often mixed with low HLB ratio emulsifiers to assist with both oil in water and water in oil emulsions. Polysorbate 60 finds applications in products that require foaming, aeration, and blending of oils and water bases. In skincare and cosmetic products, it is primarily used as a surfactant, emulsifier, and solubilizer. As a surfactant, it works by lowering the surface tension of substances such as two liquids or liquid and a solid. The hydrophilic end is attracted to the water molecule, whereas the lipophilic end is attracted to oil. Such a structure allows the surfactant to suspend oil, dirt, and other impurities that have accumulated on the skin. Surfactant properties come in handy in body washes, shampoos, and cleansers. As an emulsifier, as it helps the water and oil-based ingredients to blend and maintain the desired integrity. Adding Polysorbate 60 helps to improve the consistency of a product and enables an even distribution of topical skincare benefits. Finally, Polysorbate 60 acts as a solubilizer, which means that it helps other materials to dissolve in a solvent in which they would not normally dissolve. It helps to disperse oil in water, hence it is an excellent solubilizer for essential oils14.
In a daily skin-painting study of 5% solution of PS 60 on rabbits, moderate irritation was observed. When a 10% solution was tested, skin necrosis occurred. However, in further studies, there were no dermal effects from the 15% solution used for 60 consecutive days. Local inflammation also occurred after long-term administration of an undiluted polysorbate 60 solution to mouse skin. However, in the study conducted on humans, no irritation or skin changes were noticed15.The CIR Expert Panel has reviewed the data concerning the safety of Polysorbate 60 and concluded that it is safe as an ingredient in skincare and cosmetics products.
4. Polysorbate 80
Polysorbate 80 is a synthetic ingredient, synthesized through dehydration of sorbitol, esterification with oleic acid, and etherification with ethylene oxide. It requires 20 polymerized ethylene oxide per molecule of Polysorbate 80 on average. The technique used in manufacturing the material is called ‘ethoxylation of sorbitol’. As in the case of Polysorbate 60, the sorbitan is obtained by dehydrating the sorbitol, and then sorbitan is reacted with 80 units of ethylene oxide, hence the name of the compound. In the final step, one oleic acid group is added and esterified as the hydrophobic tail.
Polysorbate 80 comes in the form of viscous, yellow liquid. It has a boiling point at over 100
°C. It is characterized by high water solubility16.
Figure 4. The structure of Polysorbate 8017
Polysorbate 80 is primarily used as a surfactant, emulsifier, and solubilizer. It has an HLB value of 15 which makes it very soluble in water. It is used in the process of emulsification of oil-based and water-based ingredients by preventing them from separating. As a surfactant, polysorbate 80 is widely used in body washes, cleansers, and shampoos. It has a neutral charge, which makes it suitable for acting as a surface-active agent and hence lowering the surface tension. When used alone, polysorbate 80 is an excellent solubilizer for essential oils and as a wetting agent, viscosity modifier, anti-static agent, stabilizer, and dispersing agent. Polysorbate 80 can also improve the rinse off of anhydrous scrubs and cleansing oils18.
According to the Chemical Ingredients Review Expert Panel, Polysorbate 80 is not dermally irritating for humans. In human patch tests, the material was not sensitizing. There were no signs of irritation or sensitization observed in any subject, regardless of the time period. No carcinogenicity data on polysorbates were found in the published literature. In another study concerning the reproduction and development of fetuses, Polysorbate 80 was administered to albino rats on gestation days 6-15. No maternal mortalities were observed. Moreover, the material did not affect weight, organ weights or water consumption. No adverse fetal effects were observed, including growth, viability, or development of the fetuses. There were no observed differences in malformations between treatment groups and controls19.
5. The safety assessment of polysorbates used in natural cosmetics
Despite the general approval of polysorbates in the cosmetic industry, there are still a few concerns about the presence of ethylene oxide in those ingredients. The process of ethoxylation may lead to contamination with 1,4-dioxane, a potentially dangerous by-product. 1,4-dioxane is a known animal carcinogen that penetrates readily into the skin. According to the National Toxicology Program, ‘1,4-dioxane is reasonably anticipated to be a human carcinogen.’ Moreover, it has been linked to skin irritation20. However, the evaluation by CIR showed no dermal changes or skin sensitization but the products containing polysorbates21. The concern about ethylene oxide may be easily addressed by controlling the products through purification steps to remove it before adding the material to cosmetics.
Another concern investigated by the CIR Expert Panel is the incidental inhalation exposure from including aerosol and pump hair sprays, spray deodorants, spray body, and hand products, and spray moisturizing products. There is, however, very limited access to studies on this topic. Only one inhalation study was considered reliable. It suggests little potential for respiratory effects at relevant doses. The Expert Panel believes that the sizes of a substantial majority of the particles of these ingredients, as manufactured, are larger than the respirable range and/or aggregate and agglomerate to form much larger particles in formulation. Such ingredients make up only a small fraction of aerosols, around 4%. Coupled with the small actual exposure and small concentration at which the polysorbates are used, the Panel agreed that the incidental inhalation would not be significant and will not lead to local respiratory or systemic effects. Moreover, a lack of systemic toxicity regardless of the size of doses was observed. Little or no irritation or sensitization was noted in multiple dermal tests22.
In conclusion, polysorbates are safe as ingredients in natural cosmetics. The studies have proved that little to no harm is done to individuals using the products, regardless of the compound concentration. No breathing or skin problems were observed in a number of tests. The ethylene oxide, which raises concerns, can be easily monitored and removed from cosmetics by the process of purification. Moreover, due to its water-solubility, polysorbates are considered environmentally friendly. The presented studies indicate that polysorbates are safe for the human body and can be used as ingredients in natural cosmetics.
1 Elder, RL. (1984) ‘ Final report on the safety assessment of polysorbates’, published in Journal of the American College of Toxicology, USA
2 CIR (2015) ‘Safety assessment of polysorbates as used in cosmetics’ [Online], available at: https://www.cir-safety.org/sites/default/files/PSorba_032015_Tent.pdf (accessed: 15.02.2021)
6 Oxiteno (2018) ‘What is polysorbate?’ [Online], available at: https://www.oxiteno.us/what-is-polysorbate-20-vs-60-vs-80-uses/ (accessed: 15.02.2021) 7 New Directions Aromatics (2018) ‘Polysorbate 20’ [Online], available at:
9 Cayman Chemicals (2019) ‘Safety Data Sheet’
12 Special Chem ‘Polysorbate 60’ [Online], available at: https://cosmetics.specialchem.com/inci/polysorbate-60 (accessed: 16.02.2021)
13 The Derm Review (2020) ‘Should I avoid Polysorbate 60?’ [Online], available at: https://thedermreview.com/polysorbate-60/ (accessed: 16.02.2021)
16 The Derm Review (2020) ‘Polysorbate 80’ [Online], available at: https://thedermreview.com/polysorbate-80/ (accessed: 16.02.2021)
17 SciToys ‘Polysorbate 80’ [Online], available at: https://sci-toys.com/ingredients/polysorbate_80.html (accessed: 16.02.2021)
19 European Chemicals Agency (ECHA) ‘Information on Chemicals-Sorbitan monooleate, ethoxylated 9005-65-6. http://echa.europa.eu/information-on-chemicals’
20 National Toxicology Program (1991) ‘Polysorbate 80 (glycol): Target Organs and Levels of Evidence for TR-415’