The wrong lipstick color may spoil your mood—but the risk of the formula spoiling (or growing bacteria) is low since they don't contain any water, says Hammer. But since they're repeatedly exposed to the mouth area, he suggests replacing lip products after a year, or if you've recently been sick. Lipsticks and lip glosses contain oily ingredients that start to smell like stale cooking oil over time, according to Dubroff, who also says to look out for changes in texture. "You'll know a lipstick has gone bad when it gets hard and you can't spread the pigment on your lips; lip gloss will feel streaky and globby if you try to apply it."

　　tips：唇部用品1年更换一次。当唇油散发出不新鲜的烹饪油味道就说明已变质。

　　Nail Polish 指甲油

　　Nail polish may just be the Twinkie of the beauty world: It won't go bad from bacteria. Eventually though, lacquer will dry out and become thick and clumpy, with the pigments settling along the bottom of the bottle. Shake it, and if the formula remains separated, it's done-zo。

　　tips：指甲油不会滋生细菌，但是时间一长会干。如果摇晃之后，沉淀和油状还是分离态，就变质了。