BHA Lotion Formulation Review

Regarding your proposed formula for a liquid BHA lotion, the combination of ingredients is generally possible, but there are a few important points and recommendations to consider to ensure stability, efficacy, and safety.

Ingredient Compatibility and Solubility

• Salicylic Acid (ordinary type): This type of Salicylic Acid is not water-soluble. It needs to be dissolved in a suitable solvent. Your formula includes Butylene Glycol and Dimethyl Isosorbide (DMI), both of which are effective solvents for Salicylic Acid. The concentration of 2% is within the permitted limit for leave-on facial products.
• Licorice Extract (Licochalcone A 20%): This extract is also not water-soluble and needs to be dissolved in a glycol or similar solvent. Butylene Glycol in your formula can serve this purpose. Note that there is also a water-soluble version of Licorice Extract (Licochalcone A 1%) available if you prefer.
• Butylene Glycol and DMI: These solvents are compatible with your formula and will help dissolve the Salicylic Acid and Licorice Extract.
• Skin-mimic™, Glycoprotein, and Disodium EDTA: These ingredients are water-soluble or dispersible in water and are compatible with a water-based formula.
• Polysorbate 20: This is a solubilizer that can help disperse the less water-soluble components into the water phase, contributing to a stable liquid texture.

Recommendations and Adjustments

1. Dissolving Salicylic Acid and Licorice Extract: It is crucial to fully dissolve the Salicylic Acid and the Licorice Extract (Licochalcone A 20%) in the Butylene Glycol and DMI mixture before combining this phase with the water phase. Ensure complete clarity before proceeding.
2. Mixing Order: A recommended mixing order would be:
   • Combine Water, Disodium EDTA, and Glycoprotein (Water Phase). Mix until dissolved, avoiding heat above 40°C for Glycoprotein.
   • Combine Butylene Glycol, DMI, Salicylic Acid, Licorice Extract (Licochalcone A 20%), and Polysorbate 20 (Solvent/Active Phase). Mix until all powders are completely dissolved.
   • Slowly add the Solvent/Active Phase to the Water Phase while stirring continuously.
   • Add Skin-mimic™ and mix until uniformly dispersed.
3. pH Adjustment: Salicylic Acid is most effective at a pH between 3 and 4. The final pH of your formula should be checked and adjusted to be within this range for optimal exfoliation and anti-acne benefits. A pH between 4 and 5 might be less irritating while still effective. Ensure the pH is also suitable for the stability of other ingredients like Licochalcone A (pH 3.5-6.5) and Glycoprotein (pH 3.5-8.0). You may need to use a pH adjuster like Sodium Hydroxide solution.
4. Preservation: Your formula contains a high percentage of water and does not include a preservative. This is a critical omission for product safety and shelf life. You must add a broad-spectrum preservative system suitable for the final pH of your formula to prevent microbial growth.
5. Stability Testing: After preparing the formula, observe its stability over time at room temperature and potentially under accelerated aging conditions (e.g., elevated temperature) to check for separation, precipitation, or changes in appearance or texture.

Overall, your proposed ingredient list is a good starting point for a BHA lotion. By carefully following the mixing instructions, adjusting the pH, and adding a preservative, you can create a functional and stable product.