Compatibility of Niacinamide and Vitamin C when Layered

The concern about using Niacinamide and Vitamin C (specifically L-Ascorbic Acid) together in the same formulation is mainly due to pH incompatibility. L-Ascorbic Acid requires a low pH for stability, while Niacinamide is typically formulated at a higher, more neutral pH. Mixing them in one product at an incompatible pH can lead to degradation or conversion of Niacinamide to Niacin, causing irritation.

However, applying them in separate products, even layered on the skin, is generally acceptable and widely practiced. The issue is with the stability within a single formula, not with them cancelling each other out on the skin's surface when applied from different products. Using separate products allows each ingredient to be formulated at its optimal pH for stability and effectiveness. You can apply one product, let it absorb, and then apply the other.

Therefore, layering separate products containing Niacinamide and Vitamin C is a common and effective way to use both ingredients without the compatibility issues encountered when formulating them together incorrectly.