It’s worth casually mentioning that vitamin C serum side effects may cause some irritation among sensitive skin types, depending on the product’s potency. Vitamin C doesn’t always mix well with other ingredients either. Benzoyl peroxide and retinol are known to cancel out vitamin C when applied on top of one another. To prevent a fight between these ingredients, it’s best to rinse them off first before applying your vitamin C skincare. You can also wait 30 or so minutes in between product application.