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Unless you like the idea of smearing bacteria on your lips, don't keep your lip gloss longer than two years. It's unnatural for most women to throw out any cosmetic until it's completely used up or as hard as petrified rock, but beauty experts say your beloved makeup -- including lip gloss -- should be replaced regularly to head off deterioration and exploding germ populations. Store your lip gloss properly and you'll get the most out of those few, brief years the two of you have together.
Lip gloss kept for longer than two years starts to degrade. This is because the second that you pull the top off the tube, the compounds in the lip gloss are exposed to the oxidizing and deterioration-accelerating effects of air, heat, light and moisture. Lip gloss contains a lot of water. As the product ages, that water gradually evaporates, changing the overall chemical makeup of the gloss.
Dangers of Old Lip Gloss
You're not alone if you insist on sticking with your lip gloss well beyond the recommended shelf life date. "The Guardian" reports that one out of every five women between the ages of 30 and 40 regularly uses cosmetics that she purchased more than five years ago. The article goes on to quote Dr. Susan Blakeney, an adviser to the College of Optometrists in England, who notes that old lip gloss is infested with bacteria. The bacteria enters your body through your mouth when you are eating and drinking and can increase your chance of developing infections. Old lip gloss may also cause acne, rashes and skin irritation.
Keep your lip gloss looking good for as long as possible by storing it somewhere other than the bathroom. This may seem unnatural -- everyone keeps her makeup in the bathroom, right? -- but cosmetic chemist Ni'Kita Wilson told "Good Housekeeping" that the moisture, humidity and bright lights in the bathroom accelerate lip gloss degradation and encourage bacteria growth, not to mention yeast and mold. Keep it away from extreme heat -- for instance, don't toss it in your glove compartment during mid-July -- and never, never share it with someone else. Your lip gloss has enough bacteria on it from your mouth -- you don't need the bacteria from your friend's mouth as well. The best place to store lip gloss is in a cool, dry closet or drawer outside the bathroom.
When to Trash It
Even the most conscientiously stored lip gloss might go wonky on you before you reach the two year mark. If the texture of the lip gloss changes -- it gets clumpy, dry or appears to be separating -- get rid of it. Trash any lip gloss that's changed in color, looks oily or gives off a sharp or rancid odor. If in doubt, throw it out, especially if you purchased the lip gloss so long ago you can't remember how old it is or the last time you used it.