Formulation Advice

Regarding your existing formula with Salicylic Acid, Propylene Glycol, Polysorbate 20, and water, you are asking about adding Azelaic Acid (Liquid Azelaic™), Capryloyl Salicylic Acid (LHA) Liquid, Licorice Extract (Licochalcone A 1.5%), and using Pro Polymer™ for thickening.

Ingredient Compatibility and Concentration

Adding multiple exfoliating acids like Salicylic Acid (BHA), Azelaic Acid, and Capryloyl Salicylic Acid (LHA) to a single formula, especially at high concentrations, can significantly increase the risk of skin irritation and over-exfoliation.

• Salicylic Acid (BHA) and Azelaic Acid: Combining 2% Salicylic Acid with 10% Liquid Azelaic™ is a high concentration of exfoliants. It is generally recommended to use lower concentrations if combining these ingredients to minimize irritation. For example, a combination of 1% Salicylic Acid and 5% Liquid Azelaic™ might be less irritating while still providing benefits.
• Capryloyl Salicylic Acid (LHA): LHA is also an exfoliant. Adding 5% LHA (assuming the liquid form has similar activity to the powder) on top of BHA and Azelaic Acid is likely too aggressive for the skin. Capryloyl Salicylic Acid powder is typically recommended at usage rates not exceeding 2%. It is advisable to choose one or two exfoliating acids at appropriate concentrations rather than combining all three at high percentages.

Licorice Extract and pH

Licorice Extract (Licochalcone A 1%, Water-Soluble) is beneficial for reducing inflammation but requires a pH range of 3.5-6.5 for stability. A formula with 2% Salicylic Acid will likely have a pH below this range, which could cause the Licorice Extract to degrade quickly. To maintain the efficacy of the Licorice Extract, you would need to adjust the final pH of the formula upwards, ideally within the 3.5-6.5 range. However, increasing the pH might slightly reduce the exfoliating efficacy of Salicylic Acid, which is most effective at a lower pH. This is a balance you would need to consider.

Using Pro Polymer™ for Thickening

Pro Polymer™ (Gel Maker) is a suitable thickener for your water-based formula. It can create a gel texture and has good tolerance to electrolytes, which might be present from other ingredients or pH adjusters.

Mixing Instructions

Here is a suggested method for mixing your formula, considering the properties of the ingredients:

1. In a suitable container, combine the Propylene Glycol and Salicylic Acid. Stir or mix until the Salicylic Acid is fully dissolved in the Propylene Glycol.
2. In a separate container, combine the water and Polysorbate 20. Stir to mix.
3. Add the dissolved Salicylic Acid/Propylene Glycol mixture from step 1 to the water/Polysorbate 20 mixture from step 2. Stir well to combine.
4. Slowly sprinkle the Pro Polymer™ powder into the mixture while stirring continuously. Stir gently but consistently for several minutes (3-5 minutes or longer if needed) until the Pro Polymer™ is fully hydrated and a smooth gel texture begins to form. Avoid high-speed blending, as this can damage the polymer. You can also pre-disperse the Pro Polymer™ in the Propylene Glycol before step 1 for easier dissolution.
5. Once the gel has formed, add the Liquid Azelaic™ and Licorice Extract (Licochalcone A 1%, Water-Soluble). Stir gently to incorporate. Ensure the temperature is below 40°C when adding Liquid Azelaic™.
6. Check the pH of the final mixture. If you are using Licorice Extract and want to ensure its stability, adjust the pH upwards into the 3.5-6.5 range using a suitable pH adjuster (e.g., a dilute solution of sodium hydroxide). Be aware of the trade-off between Licorice stability and Salicylic Acid efficacy at higher pH.
7. Continue stirring gently until all ingredients are uniformly dispersed and the desired consistency is achieved.

Remember to test the final product on a small area of skin first to check for irritation, especially given the combination of active ingredients.