Serum Cloudiness Issue

Based on the ingredients in your serum formula (LHA, water, HPMC, allantoin, propylene glycol, glycerine, phenoxyethanol) and the expert discussion, the cloudiness that develops over time is likely due to incompatibility between certain ingredients, specifically phenoxyethanol, propylene glycol, and glycerine, within the HPMC gel base. Since the formula lacks an emulsifier, these ingredients struggle to remain fully dispersed and compatible in the water-based gel, leading to instability and the formation of a milky appearance over time.

Phenoxyethanol itself, when used correctly within its solubility limits, is generally not the cause of this type of instability. The issue arises from the overall composition and the interaction of multiple ingredients competing for solubility in the water phase thickened by HPMC.

Solutions and Alternatives

Experts have suggested the following approaches to address this issue:

1. Adjusting Mixing Order: Carefully adjusting the order of adding ingredients can help. One method is to fully dissolve phenoxyethanol in the water phase before adding other ingredients. Another suggestion is to dissolve different ingredient groups (like allantoin + propylene glycol + glycerine) in separate portions of the water phase and then combine them carefully with the HPMC gel and the phenoxyethanol/water mixture.
2. Substituting Ingredients: A more direct way to improve stability is to replace propylene glycol and glycerine with more water-compatible alternatives. Suggested alternatives include:
   • WaterLock™ (Polyquaternium-51): This ingredient helps prevent water loss and can improve the feel of the serum.
   • Liquid Hyaluronic Acid or Hyaluronic Acid Gel Base: These are highly water-soluble humectants that can provide hydration and contribute to the gel texture without causing the compatibility issues seen with propylene glycol and glycerine in this specific formula.

Regarding the use of Paraben as an alternative preservative, while Paraben (such as Sodium Paraben) is a different type of preservative, simply changing the preservative might not fully resolve the instability caused by the interaction of the other ingredients (propylene glycol and glycerine) with the HPMC gel system. Focusing on the compatibility of the humectants/solvents (propylene glycol, glycerine) with the gelling agent (HPMC) and preservative (phenoxyethanol) is key to achieving a stable, clear serum.

Trying the suggested mixing order adjustments or substituting propylene glycol and glycerine with WaterLock™ or Liquid Hyaluronic Acid/Hyaluronic Acid Gel Base are recommended steps to improve the long-term clarity and stability of your serum.