Glycols for Preservation & Penetration

Glycols are commonly used in cosmetic formulations as humectants, solvents and preservative boosters - enhancing texture, moisturization and preserving products. My primary purpose with using glycols is preservation.

BUTYLENE -  Liquid. One of the most popular ingredients used in cosmetic and skin care products. Used as a humectant, emollient and solvent – contributing to moisturizing, protecting and conditioning the skin and hair.

1,3 Butylene Glycol has COSMOS & ECOCERT Certifications

Derived from petroleum, sugarcane, or distilled corn. Water Soluble. pH 6.1. Usage Rate in skincare formulations: 1-10%. Substitute(s): Propylene Glycol

CAPRYLYL -  Liquid. Great ingredient used in thousands of products because of its hydrating and moisturizing properties. It attracts water to the topmost layer of the skin and locks it there. Caprylyl glycol is also a preservative that increases the shelf life of the products that it is used in. A humectant and preservative booster, known for it’s antimicrobial properties.

Often compliant with other standards like Ecocert, Cosmos and Natrue

Made from caprylic acid that is found naturally in coconut and palm oils however, it can also be made synthetically in labs. Water Soluble. pH 4-8. Usage Rate in skincare formulations: 1-2%. Substitute(s): Propylene Glycol

DECYLENE – AKA: 1,2-Decanediol. Liquid. Synthetic that softens skin by acting as a skin conditioner. Makes products easier to apply and can improve the penetration of other ingredients. Can also increase viscosity.

Several sources indicate that decylene glycol is allowed and even encouraged in Ecocert and COSMOS certified formulations

A synthetic substance derived from azelaic acid and sebacic acid. Soluble in Alcohol. pH 3-10. Usage Rate in skincare formulations: 0.1-2%. Substitute(s): Caprylyl Glycol, Pentylene Glycol, Squalane

GLYCOL DISTEARATE – Waxy solid. An opacifier and pearlizing agent used in cleansing products, making them white and glossy – can also give body to shampoos, creams and emulsions.

Because it can be derived from natural sources, glycol distearate is often considered acceptable for use in Ecocert-certified products

An ester of stearic acid and ethylene glycol. Insoluble in water. Dispersible in water & oil. Usage Rate in skincare formulations: 1-4%. Substitute(s): Glycol Stearate

GLYCOL STEARATE -  Waxy solid. Acts as an emollient and texture enhancer, contributing to the smooth and luxurious feel of creams, lotions and moisturizers as well as an emulsifier, thickener and stabilizer.

Not generally Ecocert certified

Derived from stearic acid and ethylene glycol. Insoluble in water but soluble in alcohols, oils & some esters. pH neutral. Usage Rate in skincare formulations: 2-4%. Substitute(s): cetearyl alcohol, glyceryl stearate, cetyl alcohol.

HEXYLENE -  Liquid. Acts as a solvent, humectant and viscosity agent – dissolving other ingredients and enhancing product stability.

Not considered an EcoCert or cosmos approved ingredient

Typically synthesized by the reaction of ethylene oxide with n-butanol or by the hydration of 1,5-hexadiene. pH 7. Water soluble. Usage Rate in skincare formulations: 0.1 - 10%. Substitute(s): Propylene glycol, butylene glycol, glycerin

PENTYLENE -  Liquid. A versatile compound used as a solvent, humectant and preservative – often as an alternative to propylene glycol due to it’s lower risk of allergic reactions.

Ecocert and COSMOS approved

Naturally derived from sugar cane but manufactured in a lab due to it’s high consumption. pH 7.5. Soluble in water & oil. Usage Rate in skincare formulations: 0.5 - 5%. Substitute(s): propanediol 1,3, butylene glycol, caprylyl glycol

POLETHYLENE (PEG’s) – Typically a wax. A group of compounds used as surfactants, emulsifiers, cleansing agents, humectants and skin conditioners. Improves the texture of the surface and also as a thickener that enhances the consistency of the product. According to NIH (National Institute of Health), many PEG types are hydrophilic and used as penetration enhancers, especially in topical dermatological preparations.

Ecocert prohibits the use of polyethylene glycol (PEG) in products seeking their certification

Synthetic, petroleum-derived compound produced through the polymerization of ethylene oxide. Water soluble. pH 7. Usage Rate in skincare formulations: Up to 100%, however concentration of PEGs used in skincare formulations can vary widely depending on the specific PEG compound and its intended use. Substitute(s): Hydrogenated Jojoba Oil

PROPANEDIOL 1,3 – Liquid. A type of glycol. Preservative-boosting humectant as well as an emollient which means that apart from adding moisture to the skin, it also reduces moisture loss from the skin. Additionally, it is an excellent solvent and dissolves all the other ingredients in a formulation. Works synergistically w/glycerin for a less sticky feel.

Ecocert Approved

Made either naturally or synthetically. It is extracted from either corn sugar or corn glucose. Water Soluble. pH4.5-7. Usage Rate in skincare formulations: 1-10%. Substitute(s): propylene glycol.

PROPYLENE – Liquid. A popular humectant, solvent and viscosity agent, helping to retain moisture and dissolve other ingredients. It is also considered safe for use in cosmetic products. Has the ability to absorb water and bring it to the outermost layer of the skin, thus enhancing the appearance of the skin by restoring suppleness and reducing flakiness.

Not an Ecocert-approved ingredient.

Derived from either natural gas, petroleum, or vegetable sources. Water Soluble. pH 9.3-10.5. Usage Rate in skincare formulations: 1-8%. Substitute(s): Glycerin, Propanediol 1,3

Benefits of Using Glycols in Skincare Products:

MOISTURIZING – Glycols, particularly humectants like Propylene Glycol and Pentylene Glycol, help draw moisture into the skin, preventing dryness and promoting hydration.

SOLVENT PROPERTIES -  They act as solvents, dissolving other ingredients in a product, ensuring even distribution and stability.

TEXTURE ENHANCEMENT – Glycols contribute to the smooth and luxurious feel of cosmetic products, making them easier to apply and absorb.

PRESERVATION – Some glycols like caprylyl glycol, act as preservative boosters, extending the shelf life of products by inhibiting microbial growth.

SKIN PENETRATION ENHANCERS – Glycols can enhance the penetration of other active ingredients into the skin, improving their effectiveness.

When it comes to using glycols as preservative boosters, keep in mind the “hurdle technology”, where it involves creating an environment that is difficult for microorganisms to survive by combining several preservation strategies rather than relying on a single preservative.

How it works: 

These "hurdles" can include:

• pH adjustment: Lowering the pH to an environment less hospitable to microbes. Most bacteria are neutrophiles, meaning they grow optimally at a pH within one or two pH units of the neutral pH of 7, between 5 and 8. Try to formulate at around 4.8 if the specific product you are making, allows it.

• Water activity reduction: Using ingredients that absorb water and reduce its availability for microbial growth. Use ingredients like salts, glycols, polyols, humectants, and amino acids, which bind water and make it less available for microbial growth.

• Chelators: bind to metal ions, preventing them from reacting with other ingredients, thus improving product stability, preventing discoloration, and enhancing the effectiveness of preservatives and other active ingredients. They bind up trace metal ion contaminants in your water-containing cosmetic thus keeping the product microbe free for longer. Use EDTA

• Emulsion type: Choosing emulsion structures that limit microbial growth. W/O emulsions. These emulsions, where water droplets are dispersed in an oil phase, are generally more stable and less susceptible to microbial contamination compared to O/W emulsions. Reducing the size of emulsion droplets to the nanoscale (nanoemulsions) can improve the effectiveness of cosmetics, including enhancing antimicrobial activity – use high pressure homogenizers for this.

• Packaging: Using protective packaging to prevent contamination. 

• Antimicrobial ingredients: Incorporating ingredients with natural antimicrobial properties. Essential Oils like Tea Tree and Lemongrass.

• Good manufacturing practices: Maintaining high standards in manufacturing to minimize contamination.