Phenoxyethanol Compatibility with Ethoxylated Compounds

It is correct that using Phenoxyethanol with ethoxylated compounds, such as polysorbates, PEG esters, and certain surfactants, can potentially reduce its effectiveness as a preservative.

Why does this happen?

Ethoxylated compounds, particularly non-ionic surfactants, can form structures called micelles in a formulation. Phenoxyethanol, being somewhat lipophilic (oil-attracting), can partition or move into these micelles. When Phenoxyethanol is trapped within the micelles, its concentration in the surrounding water phase (where most microorganisms grow) is reduced. This lower concentration in the water phase can decrease its ability to effectively preserve the product.

Identifying Ethoxylated Compounds

Identifying ethoxylated compounds often involves looking at the ingredient's name. Common indicators include:

• PEG- followed by a number (e.g., PEG-100 Stearate)
• Polysorbate followed by a number (e.g., Polysorbate 20, Polysorbate 80)
• Names containing -eth- followed by a number, indicating ethoxylation of a fatty alcohol or acid (e.g., Laureth-4, Ceteareth-20, Steareth-10). Your understanding that ingredients like Disodium Laureth Sulfosuccinate fall into this category is correct, as the "Laureth" part signifies ethoxylation. Note that Disodium Lauryl Sulfosuccinate, which contains "Lauryl" instead of "Laureth", is chemically different and not ethoxylated in the same manner.

Implications for Formulations

While the interaction exists, it doesn't necessarily mean you can never use Phenoxyethanol with ethoxylated ingredients. The extent of the reduction in efficacy depends on several factors, including the specific ethoxylated compound, its concentration, the concentration of Phenoxyethanol, and the overall formulation composition.

It is crucial to perform challenge testing on your final formulation to ensure that the preservative system, including Phenoxyethanol, remains effective against microbial growth even in the presence of other ingredients like ethoxylated compounds. This testing is the most reliable way to confirm the stability and safety of your product.

Products like Phenoxyethanol (Extra Pure), Phenoxyethanol SA (eq. Optiphen Plus), Chlorphenesin / Phenoxyethanol (Microcare PHC eq.), and Phenoxyethanol P5 are examples of Phenoxyethanol-based preservatives available.