First Combo: Azelaic Acid + Vitamin C: Azelaic acid helps calm down inflammation, kills off acne causing bacteria and can treat post acne marks. When you use it with Vitamin C, it multiplies the effectiveness of the Azelaic Acid (helps even out the skin tone)
Second Combo: Retinol (Vitamin A) + Niacinamide: When you pair these together, the Niacinamide helps your skin tolerate the Retinol.
Third Combo: Hyaluronic Acid + Vitamin C: Pairing these two together, you are essentially getting an extra boost for brightening your skin. While Hyaluronic Acid is hydrating your skin, the Vitamin C will be brightening it. It also helps fight wrinkles :)
>>When layering products, make sure you apply them from thinnest to thickest.
>>It may not be the same for everyone.