Retinol & Alpha Hydroxy Acid: Both vitamin A derivatives, like retinol and retinoids, and alpha hydroxy acids (AHAs), like glycolic acid, are a dermatologist’s go-to for anti-aging because they speed skin cell turnover and increase collagen production for glowy, fine line–free skin. In this case, though, more is not better.
Retinol & Vitamin C: “Vitamin C is a tough ingredient to formulate with because it’s most effective in an acidic pH environment. Retinol works in a higher (more alkaline) pH. If using them together, they won’t work optimally,” says Sikora.
Retinol & Salicylic Acid: To fight the good fight against acne, you may also use salicylic acid, a beta hydroxy acid (BHA). But together they should be combined with caution. The risk is over-drying, which can lead to irritation and make the situation worse.