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年更換一次。當唇油散發出不新鮮的烹飪油味道就說明已變質。

　　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：指甲油不會滋生細菌，但是時間一長會干。如果搖晃之后，沉淀和油狀還是分離態，就變質了。