Solutions to Maintain Cream Effectiveness

Potential Causes

Based on your formula, particularly the inclusion of Alpha Arbutin and Niacinamide, and the issue of decreased effectiveness (whitening and smoothness) after about 3-4 weeks, the main reasons are likely:

• Degradation by Light: Certain active ingredients, such as Alpha Arbutin, are sensitive to light, especially UV light, which can accelerate their decomposition.
• Interference from Metal Ions: Trace amounts of metal ions that might be present in ingredients or water can react with active compounds, leading to a reduction in effectiveness.

Recommended Solutions to Maintain Effectiveness

To help your cream maintain its whitening and smoothing effectiveness for a longer period, consider implementing the following adjustments:

1. Use Opaque Packaging: Avoid using clear jars that allow light to pass through easily. UV light is a significant factor in the degradation of many active ingredients. Using opaque containers will effectively protect your formula from light exposure.
2. Add Disodium EDTA to the Formula: Include Disodium EDTA at a concentration of approximately 0.2% in the water phase before adding other ingredients. Disodium EDTA acts as a chelating agent, binding to metal ions that may be present in the formula. This prevents these ions from interfering with or accelerating the degradation of active ingredients, thereby increasing the stability of the formula.

Your current pH adjustment to 5.5-5.8 is within the suitable range for both Alpha Arbutin and Niacinamide. Storing the cream in the refrigerator is also a good practice to slow down degradation. However, protecting from light and metal ions are crucial steps to address the issue of rapid loss of effectiveness.

In summary, protecting your cream from light and incorporating Disodium EDTA are the most effective ways to enhance its stability and extend its period of effectiveness.