Today’s personal care and cosmetic industry faces a combination of challenges as it seeks to maintain the integrity and safety of its products and respond to market trends and consumer opinions regarding preservatives. As the effects of preservatives are largely preventive, i.e., of microbial growth and product degradation, it is easy for consumers and others who do not see or appreciate their benefits to dismiss preservatives as unnecessary or potentially harmful. At R&D’s forefront is the ongoing scientific evaluation of preservatives and the need to communicate their safety and ability to protect products from microbial growth—in support of their continued use. In this second in a series of articles, the authors review phenoxyethanol, a commonly used preservative in personal care products and cosmetics; the first article, “The Importance of Formaldehyde-Donor Preservatives in Personal Care Products,” was published in July 2013.
Antimicrobial Efficacy and Formulation Considerations
The ingredient 2-phenoxyethanol (phenoxyethanol) is well-known for its antimicrobial efficacy against a range of microorganisms, and it is particularly effective against Gram-negative microorganisms such as Pseudomonas species. It is used as a preservative in both leave-on and rinse-off personal care products. Introduced in the 1950s, it has had a long history of safe use as a cosmetic preservative. In recent years, the use of phenoxyethanol has expanded due to its low sensitization potential and global approval. Although the phenoxyethanol used in personal care is typically synthetic, it does occur naturally in green tea. The natural form has been employed to preserve “natural” personal care products. In addition to its function as a preservative, phenoxyethanol is used as a solvent for low water-soluble cosmetic ingredients such as fragrances and other preservative actives.
A member of the glycol ether family, phenoxyethanol is the product of the reaction of ethylene oxide with phenol. It is a free-flowing liquid and light in color, with a mild rose odor. Cosmetic grades are of high purity and do not impart free phenol, odor or color to the final formulation. A high purity grade of this preservative is recommended to avoid odor issues, especially in personal care wipes.
Phenoxyethanol is compatible with most cosmetic raw materials used in rinse-off and leave-on products. Its thermal stability (up to 85°C) facilitates viability through numerous manufacturing processes and use in a broad range of products types. It has functional activity and efficacy at a pH range of 3 to 10, and is typically well-dispersed throughout a formulation, although changes in viscosity have been observed in some formulations, depending on the thickening mechanism and use level.