Yes, it’s perfectly safe to use. The high concentration of niacinamide and caffeine in the serum can cause moisture to evaporate when exposed to air, leaving behind the "powder" form of the active ingredients, which may appear white. Simply wipe off any residue from the surface or cap, secure the lid tightly, and you can continue using the product as normal. The efficacy remains unaffected.

Caffeine in cosmetics only works on the skin and does not impact the nervous system, so it won’t interfere with your sleep. While it may have a stimulating effect on the skin, it will not disrupt your sleep.