What is the difference between mineral and chemical sunscreen?

Mineral sunscreens use zinc oxide or titanium dioxide to physically reflect UV rays away from the skin. They work immediately on application and tend to suit sensitive skin well because the actives sit on top rather than absorbing into skin. The trade-off is that traditional mineral formulas can leave a white cast, though modern formulations have improved significantly. Chemical sunscreens use filters like avobenzone and octisalate that absorb UV rays and convert them to heat. They tend to feel lighter under makeup but require about 20 minutes to become active after application. For mature, reactive skin, mineral or hybrid formulas are often the more comfortable choice.