Wait for 1-2 minutes for the alpha arbutin to penetrate your skin's deeper layers before going in with your other serums or moisturizers.For brighter skin complexion, layer it with AHAs /BHAs. Apply direct acid, hyaluronic acid, and then alpha arbutin serum. People with sensitive skin can use niacinamide instead of AHA/BHA along with alpha arbutinSince it lessens the production of melanin, the skin should always be protected with a high SPF 30 and above sunscreen to avoid sunburn.Although this serum is proven to show effect in 4-5 weeks for full benefits, it is recommended to be used religiously for 2-3 months daily. Since it is also a preventive serum, keep using it to avoid new dark patches.Note: For external use only. Patch test recommended before use.