AHA 10% and BHA 2% Formulation pH

Regarding your formulation with 10% AHA and 2% BHA at pH 4.08, both ingredients will have some exfoliating activity at this pH.

However, for optimal effectiveness, especially for Salicylic Acid (BHA), a lower pH is generally preferred. Salicylic Acid's activity is highly dependent on pH, with more free acid available at lower pH levels within its effective range of 2-4. At pH 4.08, a significant portion of the Salicylic Acid will be in its less active salt form.

Adjusting the pH down to 3.5 would increase the amount of free Salicylic Acid, making the 2% concentration significantly more potent for exfoliation and penetrating pores. Similarly, lowering the pH to 3.5 would also increase the effectiveness of the 10% AHA.

Therefore, while pH 4.08 provides some benefit, adjusting the pH to 3.5 would likely result in a more effective product in terms of exfoliation and treating concerns targeted by AHA and BHA.

Important Consideration: Lowering the pH increases the potency but also the potential for skin irritation, redness, and sensitivity, especially with a combined concentration of 10% AHA and 2% BHA. It is advisable to test the product on a small area first and introduce it gradually into your routine.