Answer to Questions about LHA

1. Stable pH Range for LHA

LHA (Capryloyl Salicylic Acid) is stable in an acidic to weakly acidic pH range, approximately pH 2-6.

2. pH Adjustment in the Formula

Regarding the formula you provided (LHA 10%, Propolymer 1%, Mild Preserve 0.5%, Water), there are important points to consider before discussing pH adjustment:

• Solubility Issue: LHA is oil-soluble, not water-soluble. Using 10% LHA in a formula that is primarily water-based will result in the LHA not dissolving and not being well dispersed in the product.
• Concentration Issue: The recommended usage rate for LHA is 0.5-5%, with a recommendation not to exceed 2% due to potential for significant irritation. Using LHA at 10% is very high and is likely to cause severe skin irritation.

Due to these fundamental issues with solubility and excessively high concentration, the formula you provided is not practically usable as written. Therefore, pH adjustment is not the primary concern in this case.

If you wish to use LHA in a formula, you should revise the mixing method by dissolving LHA in an oil phase (if applicable) or using appropriate solubilizers, and reduce the concentration to a safe and recommended range (not exceeding 2% for general use).

If the solubility and concentration issues can be resolved and a suitable formula is achieved, controlling the pH to be within 2-6 will help ensure LHA stability, and within 2-9 for Propolymer to function effectively as a gelling agent. Additionally, if the product is intended for sale, you may need to consider adjusting the pH to 3.5 or higher according to FDA regulations.