Preservative Usage in Serum

Here is information regarding the use of Phenoxyethanol (Optiphen) and a comparison with Global Guard for your serum formulation:

1. Phenoxyethanol (Optiphen) Usage Percentage

For Phenoxyethanol, including the Extra Pure grade (often referred to as Optiphen), the general recommended usage rate in cosmetic formulations is 0.5% to 1.0%. For products applied around the eyes, the usage rate should not exceed 0.5%. Using the Extra Pure grade specifically helps to reduce the risk of skin irritation compared to standard Phenoxyethanol.

If you require broad-spectrum protection (against both bacteria and fungi), Phenoxyethanol alone is not sufficient. In such cases, a blend like Phenoxyethanol SA (equivalent to Optiphen Plus), which contains Phenoxyethanol, Caprylyl Glycol, and Sorbic Acid, is recommended. Phenoxyethanol SA has a usage rate of 0.5% to 1.25% depending on the product type (up to 1.0% for closed containers like serums, and up to 1.25% for open containers). This blend can also be less irritating than using Phenoxyethanol alone at higher concentrations.

2. Phenoxyethanol (Optiphen) vs Global Guard

Comparing Phenoxyethanol (Optiphen) and Global Guard involves considering their effectiveness, required pH range, and potential for irritation:

• Phenoxyethanol (Extra Pure) / Optiphen: Effective against bacteria but less effective against fungi. It is not considered a broad-spectrum preservative on its own. It is effective in formulations with a pH between 2 and 9. The Extra Pure grade is specifically designed to be less irritating.

• Global Guard™: This preservative is effective at inhibiting germs but has a significant limitation: it is only effective in formulations with a pH less than 5.5. It is not suitable for formulas containing Vitamin C. Its main components are Sodium Benzoate and Potassium Sorbate.

• Global Guard™ 221: This is a broad-spectrum, water-soluble preservative effective in formulations with a pH between 2 and 7. It is used at a low rate (0.5-1.1%) and is globally approved.

• Phenoxyethanol SA (eq. Optiphen Plus): This blend provides broad-spectrum protection and is effective in formulations with a pH between 2.0 and 6.0. It is often preferred over Phenoxyethanol alone when broad-spectrum activity is needed and may offer reduced irritation compared to using Phenoxyethanol alone at higher levels.

Which is better and less irritating?

• For broad-spectrum protection, neither Phenoxyethanol (Optiphen) alone nor Global Guard™ (pH < 5.5) are ideal choices. Broad-spectrum options like Phenoxyethanol SA (Optiphen Plus) or Global Guard™ 221 would be more suitable for a serum.
• Regarding irritation, the Extra Pure grade of Phenoxyethanol is formulated to reduce irritation. Phenoxyethanol SA may also be less irritating than using Phenoxyethanol alone at higher concentrations. The descriptions for Global Guard™ and Global Guard™ 221 do not provide a direct comparison of irritation levels against Phenoxyethanol, but Global Guard™ 221 is used at a low concentration.

Ultimately, the best choice depends on the specific pH of your serum formulation and whether you require broad-spectrum protection. If your serum has a pH below 6.0, Phenoxyethanol SA is a strong broad-spectrum option. If your pH is between 6.0 and 7.0, Global Guard™ 221 is a suitable broad-spectrum choice. If your pH is above 7.0, Phenoxyethanol (Extra Pure) could be used, but you would need to combine it with another preservative effective against fungi for broad-spectrum coverage. Always perform a challenge test to confirm the effectiveness and suitability of the chosen preservative in your specific formula.