When you go to the beach or pool this summer, sunscreen is a must-have item. But leaving a bottle exposed to the sun can make it useless; high heat can kill the active ingredients in sunscreen, making your lotion worthless. To keep your sunscreen active, try placing it somewhere cool, like a cooler with ice. Or fill a reusable cup with cold water and place the bottle inside. And when you get home from a day of fun in the sun, store the sunscreen in a cool, dark place.