Pentylene glycol

Pentylene glycol is an antimicrobial, chemically or naturally produced humectant that has been listed in the German Drug Codex® since 2009. However, it is not only approved in Germany, but now also worldwide as a cosmetic active ingredient. Originally, it was based on the unripe juice of sugar beets, but synthetic production is now standard. The usual processes include hydrogenation of furfural with molecular hydrogen and iron(II) chloride on a so-called platinum catalyst.

Where is pentylene glycol used?

The substance belongs to the group of hydroxyl group-containing substances such as ethanol, glycerol and sorbitol. It is a colorless and viscous liquid that is miscible with water and has a boiling point of 242 degrees Celsius.

It is increasingly used in cosmetic products these days, although there are many other uses. For example, pentylene glycol is widely used as a solvent and as a plasticizer in the plastics industry. It is also frequently integrated into cleaning products. The substance has both moisture-binding and antimicrobial properties. As a dihydric alcohol, in a certain concentration it prevents undesirable microorganisms from multiplying. We are also familiar with this effect, for example, from brandy with a high alcohol content, which does not need to be preserved and is even suitable for disinfection in some cases. Normally, microorganisms form very quickly in cosmetic products such as water/oil emulsions, so suppliers must do everything possible to exclude the multiplication of fungi and bacteria. However, conventional preservatives have no benefit for the skin, on the contrary, in many cases they can even cause harm.

What are the positive properties of pentylene glycol in cosmetics?

Pentylene glycol, on the other hand, is classified neither as hazardous to health nor as toxic, since the substance cannot be detected in urine or human tissue. It is therefore considered to be harmless. Thanks to its very good tolerability, skin sensitization is also virtually ruled out. Another immensely important advantage of pentylene glycol is that, in contrast to conventional alcohol, it does not have a drying effect even at higher dosages. Pentylene glycol also has a positive effect on the stability as well as on the haptic properties of various emulsions by influencing the droplet size.

Due to its dual function (firstly as a humectant and secondly its antibacterial effect), pentylene glycol is not listed as a classic preservative in the Cosmetics Regulation. This means that a product containing pentylene glycol may be labeled “Free of preservatives” without further ado, and the requirements of the Cosmetics Ordinance are nevertheless complied with absolutely correctly.

In any case, classic preservatives are suspected of causing or promoting allergies. Pentylene glycol, on the other hand, is a gentle alternative with a low allergy risk. The substance has already proven its worth in many a high-quality cosmetic product and can be optimally integrated into many formulations.

Now also in the even more compatible “green” variant

Recently, an even more compatible variant of pentylene glycol has become available, based on sugar cane residues and corn spindles. It offers the same positive properties as the chemically produced variant, but its novel natural origin opens up interesting application possibilities here in eco-certified cosmetic products. In this way, the degree of naturalness in the desired cosmetic products is increased, while the so-called ecological footprint is reduced. Sustainably produced pentylene glycol is the first “green” alkanediol ever to be able to optimally preserve cosmetic formulations as the sole antimicrobial active ingredient. The substance also has the ability to improve the overall skin feel of cosmetic products. This has been demonstrated in studies with volunteer test subjects. While the results for formulations with glycerin and conventional 1,3-propanediol were rather average, products with “green” pentylene glycol scored best in seven of a total of eight categories.

Particularly positive mentions were made of “Low stickiness” and “Rapid absorption through the skin”. These very impressive results underline the very good skin care properties of the natural variant.

Due to its plant-based origin, it really does make sense to use the green variant in cosmetic formulations, especially since product safety has now also been proven. Extensive tests with more than 100 volunteers and a test duration of 40 days did not reveal any signs of sensitization or skin irritation in any of the test subjects. It can therefore be assumed that pentylene glycols made from natural raw materials are just as safe and mild as the synthetically produced variant. Even the expert panel of the “CIR” (Cosmetic Ingredient Review) came to a similarly positive assessment in its final safety report, which was published some time ago. Green pentylene glycol convinces with an outstanding multifunctionality, which includes the basic pillars “moisturization of the skin”, “antimicrobial protection” as well as the “improvement of sensory properties”.

Pentylene glycol as an ingenious all-rounder

If pentylene glycol is combined with classic or alternative preservatives, the effect is even stronger. Their preservative properties are significantly improved by the use of pentylene glycol. Optimized mixtures of “green” pentylene glycol and the conventional preservatives sodium benzoate and benzoic acid have already proved successful. Similarly positive results have been obtained with combinations of pentylene glycol with phenylpropanol and glyceryl caprylate.

PROFILE:

INCI: Penthylene Glycol

CAS number: 111-29-5

Alternative names: Pentanediol, pentane-1,5-diol, pentamethylene glycol.

Properties: Humectant, solvent, antimicrobial effect.

Melting point: minus 16 degrees Celsius

Conclusion: Excellent as a humectant and preservative

As a bivalent alcohol, pentylene glycol not only prevents the proliferation of harmful microorganisms, but also simultaneously ensures that the skin does not dry out. Anyone who wants to offer sophisticated cosmetics that are free of artificial preservatives and still prevent possible contamination will find the substance a perfect solution.

Pentylene glycol can be used in a cream or balm just as well as in shower gel or an oil-free fluid. The substance is even compatible with water-free formulations (for example, lipsticks).

The application concentrations are usually between three and five percent; if the substance is mainly used for preservation, concentrations of five to seven percent are the rule.

Although pentylene glycol is generally considered to be highly recommendable, the new “green” variant can top the positive properties.

Feel free to ask us if we can reformulate your preservative system to “green.”

Literature:

1,2 Pentanediol-a Multifunctional ingredient for Personal Care Applications; R. Pillia, G. Schmaus, S. Lange, J. Roeding; SOFW 06-2005; S. 13-22

Ein zeitloser, multifunktionaler Kosmetikbestandteil; Y. Sander, R. Pillai; Pentylenglykol; SOFW 12-2018; S. 18-25

Sustainable and Multi-purpose, bio-based pentylene glycol; S. Behnke, Y. Sander, M. Larnicol, J. Couplet, S. Lange, J. Claus; SPC 10-2018; S. 50-52

Pentylene glycol: An emerging cosmetic allergen?

Corazza M, Schenetti C, Schettini N, Zedde P, Borghi A.Contact Dermatitis. 2022 Jan;86(1):44-46