It is common to read that vitamin C and niacinamide, although effective on their own, are not compatible. Their combination would neutralize their effects. Similarly, it is reported that the two compounds could potentially react to produce nicotinic acid, which can lead to skin reactions such as redness, itching, and temporary irritations. However, such a phenomenon occurred when pure vitamin C and niacinamide were formulated and maintained at high temperatures.
For improved chemical stability in topical formulations, most skincare products nowadays contain derivatives of Vitamin C, such as ascorbyl tetraisopalmitate, sodium ascorbyl phosphate, tetrahexyldecyl ascorbate, ascorbyl glucoside, etc.
However, given that they offer similar benefits and target the same skin concerns, it would be logical that their combined use could, in a sense, enhance their effects. Indeed, scientists suggest combining them. Even though they provide the same advantages, niacinamide and vitamin C work in synergy through different biological mechanisms to exert their effects. They thus address skin issues from different angles and would therefore be complementary.
It would therefore apparently be relevant to combine these two active ingredients to enhance their effects on the concerns they address, without skin reactions and without impacting their efficacy. Indeed, studies have shown that it is possible to safely mix them, whether together in the same formulation or in layers using different products, particularly as a solution to photoaging and irregular skin pigmentation.
Indeed, such a combination of active ingredients in a topical formula would have a more significant effect on the reduction of the melanogenesis than a single agent. Vitamin C results in a decrease in melanin synthesis by inhibiting tyrosinase, an enzyme necessary for its production, while the niacinamide prevents the transfer of melanosomes from melanocytes to epidermal keratinocytes.
This blend of active ingredients has also demonstrated a reduction in the synthesis and content of melanin pigments in the skin by modulating the oxidative stress induced by UV radiation (antioxidant property), a primary mediator of the melanogenesis process, but also by inhibiting the degradation of collagen and elastin fibers by metalloproteinases.