Unlike the linear C8 alkyl glyceryl ether (caprylyl glyceryl ether), which melts at approximately 69 °C, 2-ethylhexylglycerin features a branched alkyl chain, making it liquid at room temperature. It is a multifunctional cosmetic ingredient known for boosting the preservative efficacy of phenoxyethanol, methyl paraben, and 1,2-glycols. The preservative-enhancing activity of ethylhexylglycerin is attributed to its amphiphilic, surfactant-like molecular structure, which facilitates increased membrane permeability and allows greater intracellular uptake of co-preserved antimicrobial agents.
Ethylhexylglycerin has very low water solubility, which can limit its effectiveness in water-rich formulations. The addition of 10% ethanol, propylene glycol, dipropylene glycol, butylene glycol, or glycerin increases its solubility in water to only about 0.2–0.3%. Therefore, its limited solubility should be considered when higher concentrations are needed.
It is stable against hydrolysis and heat, and demonstrates excellent compatibility with commonly used cosmetic ingredients. Additionally, it is pH-insensitive and remains effective across a wide pH range, up to pH 12. Allergic reactions to ethylhexylglycerin are rare and considered unlikely.
Ethylhexylglycerin is effective on its own against Gram-positive bacteria such as Corynebacterium and Staphylococcus species, which are primarily responsible for sweat breakdown and body odor, while preserving the natural balance of healthy skin bacteria. Reported minimum inhibitory concentrations (MIC) of ethylhexylglycerin for various bacterial strains are as follows:
- Escherichia coli – 0.25%
- Bacillus subtilis – 0.15%
- Staphylococcus aureus – 0.19%
- Pseudomonas aeruginosa – 1%
