Formula Suitability, pH, and Combination of AHA, Tranexamic Acid, and Vitamin B3

Regarding your questions about the formula containing 10% Glycolic acid (AHA), 5% Tranexamic acid, and 5% Vitamin B3 for treating melasma, whitening, and exfoliation:

1. Is this formula usable and appropriate?
   This formula can be used, but it is recommended for nighttime use only, with strict avoidance of sun exposure during the day. The concentration of Tranexamic acid at 5% exceeds the limit allowed by the FDA for cosmetic products (which is a maximum of 3%). Using a concentration of 5% would require the product to be registered as a drug. The concentration of AHA at 10% is at the upper limit permitted for consumer cosmetics (FDA allows up to 10% with a pH of 3.5 or higher). Using these ingredients together at high concentrations, especially AHA and Tranexamic acid, may increase the potential for skin irritation.

2. Is a pH of 3.5-3.7 suitable, and what pH is optimal for Glycolic acid and Tranexamic acid efficacy?
   A pH of 3.5-3.7 is suitable. This pH range allows Glycolic acid (such as Glycopure or Ampho-Glycolic) to work effectively for exfoliation while also meeting the FDA requirements for consumer AHA products (pH not lower than 3.5). Glycolic acid's efficacy is significantly reduced at pH levels above 4.0. For Tranexamic acid (like Tranexamic Acid (Trans-White) or Nano-TXA), the optimal pH range is 3-8, so 3.5-3.7 is well within this range. Vitamin B3 (such as Safe-B3 or Extreme-B3) is also stable and effective in the pH range of 3-8, with 4.0-7.0 being considered optimal, so 3.5-3.7 is acceptable.

3. Should skin whitening and exfoliation be separate or combined?
   It is possible to combine ingredients for skin whitening and exfoliation in the same formula, particularly in a leave-on product intended for overnight use. Exfoliation with AHA helps to remove dead skin cells, which can improve the penetration and effectiveness of whitening ingredients like Tranexamic acid and Vitamin B3, potentially leading to faster results. Products like Specialist B3 Serum demonstrate that combining these ingredients is feasible. However, as mentioned earlier, combining multiple active ingredients at high concentrations increases the risk of skin irritation compared to using them separately or at lower concentrations. If you choose to combine them, start with caution and observe your skin's reaction.