Issues with BHA Gel Formulation: Solubility and Compatibility

Regarding your BHA GEL formulation and questions, based on the staff's evaluation:

1. Salicylic Acid in Isopentyldiol: The staff indicated that dissolving Salicylic Acid in Isopentyldiol at this concentration might be possible with heat initially, but it is unlikely to remain stable long-term and may lead to precipitation. They did not suggest an alternative solvent in this specific context, but the overall feedback implies the formula structure needs revision.
2. Adding Mandelic Acid 10%: According to the staff, Mandelic Acid needs to be dissolved in water. Since your proposed formula does not contain water, Mandelic Acid cannot be properly dissolved and incorporated, remaining as powder or sediment. Therefore, adding it to this specific formula is not feasible.
3. Stability at pH 4: The staff's primary concern is the fundamental inability to mix the formula as written due to the lack of water for water-soluble ingredients (like Mandelic Acid and Calcium Pantothenate) and the difficulty in combining the oil and non-oil phases with such a high concentration of Isopentyldiol without a suitable emulsifier. These issues lead to inherent instability (undissolved ingredients, phase separation) regardless of the pH level.
4. Omitting Disodium EDTA with DI Water: Disodium EDTA is typically used to chelate metal ions in water, which can improve stability. Using DI water (deionized water) reduces the presence of these metal ions compared to regular water, thus potentially reducing or eliminating the need for EDTA. However, whether it can be completely omitted depends on the sensitivity of other ingredients in a revised formula that includes water. This point is secondary to the main issues of lacking water and emulsification mentioned by the staff.
5. Suitability of the Formula: The staff explicitly stated that the formula "cannot be mixed" as proposed. The main reasons are:
   • Several ingredients (Mandelic Acid, Calcium Pantothenate) require water to dissolve properly, and the formula lacks water.
   • The oil-based ingredients cannot be combined stably with the other ingredients (including the high concentration of Isopentyldiol) without an emulsifier, and even with an emulsifier, the high Isopentyldiol content makes emulsification very challenging.

In summary, the formula as presented is not suitable due to fundamental issues with ingredient solubility and phase compatibility, as highlighted by the staff. Significant modifications, likely including the addition of a water phase and an appropriate emulsification system, would be required to make it viable.